Cisco uBR7100 Series Software Configuration Guide
Chapter 3: Configuring the Cisco Cable Modem Card
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Configuring the Cisco Cable Interface

Table Of Contents

Configuring the Cisco Cable Interface

Configuring the Downstream Cable Interface

Activating the Downstream Carrier

Verifying the Downstream Carrier

Setting the Integrated Upconverter

Verifying the Integrated Upconverter Configuration

Setting the Downstream Channel ID

Verifying the Downstream Channel ID

Setting the MPEG Framing Format

Verifying the Downstream MPEG Framing Format

Setting the Downstream Modulation

Verifying the Downstream Modulation

Setting the Downstream Interleave Depth

Verifying the Downstream Interleave Depth

Setting the Downstream Helper Address

Verifying the Downstream Helper Address

Setting Downstream Rate Limiting

Verifying Downstream Rate Limiting

Configuring the Upstream Cable Interface

Setting the Upstream Frequency

Verifying the Upstream Frequency

Setting the Upstream Channel Width

Verifying Upstream Channel Width

Setting the Upstream Input Power Level

Verifying the Upstream Input Power Level

Activating Upstream Admission Control

Verifying Upstream Admission Control

Activating Upstream Forward Error Correction (FEC)

Verifying Upstream FEC

Specifying Upstream Minislot Size

Verifying Upstream Minislot Size

Activating the Upstream Scrambler

Verifying the Upstream Scrambler

Activating Upstream Differential Encoding

Verifying Upstream Differential Encoding

Activating Upstream Rate Limiting

Verifying Upstream Rate Limiting

Activating Upstream Frequency Adjustment

Verifying Upstream Frequency Adjustment

Activating Upstream Power Adjustment

Verifying Upstream Power Adjustment

Activating Upstream Timing Adjustment

Verifying Upstream Timing Adjustment

Activating the Upstream Ports

Verifying the Upstream Ports

Setting Upstream Backoff Values

Verifying Upstream Data Backoff Automatic

Enabling and Configuring Baseline Privacy

Introduction to the Baseline Privacy Interface (BPI)

BPI Key Management

Differentiating Traffic Streams

CM Communication with BPI

Enabling BPI

Configuring Baseline Privacy

Configuring Key Encryption Key (KEK) Privacy

Configuring Traffic Encryption Key (TEK) Privacy

Activating Baseline Privacy

Configuring and Activating Frequency Agility

Creating Spectrum Groups

Verifying Spectrum Groups

Configuring and Activating Spectrum Groups

Verifying Spectrum Group Configuration

Verifying Frequency Hopping

Configuring Spectrum Group Characteristics

Verifying Spectrum Group Characteristics

Assigning the Spectrum Group and the Upstream Ports

Verifying Spectrum Group and Upstream Port Assignments

Activating Cable Address Resolution Protocol Requests

Activating Cable Address Resolution Protocol (ARP) Requests

Verifying ARP Requests

Activating Host-to-Host Communication (Proxy ARP)

Activating Cable Proxy ARP Requests

Verifying Cable Proxy ARP Requests

Configuring DHCP Options

Activating Cable Relay Agent

Activating DHCP giaddr

Verifying DHCP giaddr Activation

Configuring Time-of-Day Service

Activating Time-of-Day Service

Verifying Time-of-Day Service

Setting Optional IP Parameters

Activating IP Multicast Echo

Verifying IP Multicast Echo

Activating IP Broadcast Echo

Verifying IP Broadcast Echo

Activating Packet Intercept Capabilities

Configuring Cable Modulation Profiles

Configuring Cable Modulation Profiles

Verifying Cable Modulation Profiles

Configuring QoS Profiles

Verifying QoS Profiles

Setting QoS Permission

Verifying QoS Permission

Enforcing a QoS Profile Assignment

Verifying a QoS Profile Assignment

Setting Quality of Service (QoS) for Higher Priority Traffic

Configuring a QoS Profile for Higher Priority Traffic

Monitoring and Maintaining QoS for Higher Priority Traffic

Setting and Viewing Concatenation

Setting Concatenation

Viewing Concatenation Status


Configuring the Cisco Cable Interface


The Cisco IOS software command-line interface (CLI) can be used to configure the Cisco cable modem interface for correct operation on the hybrid fiber coax cable (HFC) network. This chapter describes the following tasks required to configure the Cisco cable modem card.


Note For tasks marked optional below, default settings are typically adequate to configure the system. Change default settings only with careful prior analysis.


"Configuring the Downstream Cable Interface" section

"Configuring the Upstream Cable Interface" section

"Enabling and Configuring Baseline Privacy" section (Optional)

"Configuring and Activating Frequency Agility" section

"Activating Cable Address Resolution Protocol Requests" section

"Activating Host-to-Host Communication (Proxy ARP)" section (Optional)

"Configuring DHCP Options" section

"Configuring Time-of-Day Service" section

"Setting Optional IP Parameters" section (Optional)

"Activating Packet Intercept Capabilities" section (Optional)

"Configuring Cable Modulation Profiles" section

"Setting Quality of Service (QoS) for Higher Priority Traffic" section

"Setting and Viewing Concatenation" section (Optional)

Configuring the Downstream Cable Interface

The first step in configuring the Cisco CM interface is to configure the downstream cable interface, which generally entails the downstream frequency, symbol rate, compression, and modulation. Configuring the downstream cable interface consists of the following specific tasks:

"Activating the Downstream Carrier" section

"Setting the Integrated Upconverter" section

"Setting the Downstream Channel ID" section

"Setting the MPEG Framing Format" section

"Setting the Downstream Modulation" section

"Setting the Downstream Interleave Depth" section

"Setting the Downstream Helper Address" section

"Setting Downstream Rate Limiting" section


Note In most applications, default values for the commands used in these configuration steps are adequate to configure the Cisco uBR7100 series router. You do not need to specify individual parameters unless you want to deviate from system defaults.


For information on other configuration options, see the "Cisco Cable Modem Termination System Commands" chapter in the Broadband Command Consolidation Guide, available on Cisco.com and the Documentation CD-ROM.

Activating the Downstream Carrier

To activate a downstream port on a Cisco uBR7100 series cable interface card for digital data transmissions over the HFC network, complete the steps in the following table.

 
Command
Purpose

Step 1 

CMTS01> enable

Password: password

CMTS01#

Enter enable (privileged EXEC) mode.

Enter the password.

You have entered privileged EXEC mode when the prompt displays the pound symbol (#).

Step 2 

CMTS01# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

CMTS01(config)#

Enter global configuration mode. You have entered global configuration mode when the prompt displays (config)#.

This command can be abbreviated to config t.

Step 3 

CMTS01(config)# interface cable1/0
CMTS01(config-if)#

Enter cable interface configuration mode.

In this example, the interface is downstream port 0 on the cable interface card installed in slot 1 of the Cisco uBR7100 series CMTS.

Step 4 

CMTS01(config-if)# cable downstream if-output


CMTS01(config-if)#
no cable downstream if-output

Default. Activate downstream digital data from the Cisco uBR7100 series router.

Deactivate downstream digital data. This command mutes the IF output of the cable interface card and shuts down the interfaces.

Step 5 

CMTS01(config-if)# no shutdown

Place the downstream port in the "admin up" state.

Step 6 

CMTS01(config-if)# end
CMTS01#

%SYS-5-CONFIG_I: Configured from console by console

Return to privileged EXEC mode.


This message is normal and does not indicate an error.

Verifying the Downstream Carrier

To determine if the downstream carrier is active (up), enter the show controllers cable command for the downstream port that you just configured. For NTSC 6 MHz operations, see the following example:

CMTS01# show controllers cable1/0 downstream
Cable1/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
 FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4

Setting the Integrated Upconverter

The Cisco uBR7100 series router supports an integrated upconverter that outputs a DOCSIS RF signal on the DS0 RF downstream port. To enable the integrated upconverter, you must do the following:

Set the downstream frequency—The integrated upconverter must be configured for the digital carrier frequency, which is the center frequency of the downstream RF carrier (the channel) for the downstream port. The cable downstream frequency command configures the downstream center frequency for the integrated upconverter.


Note The cable downstream frequency command has no effect on external upconverters. If you are using an external upconverter, this command is informational only and you must configure the external upconverter separately, using its own command procedures.


Enable the integrated upconverter—The integrated upconverter is disabled by default and must be enabled with the no cable downstream rf-shutdown command.

Enable the cable interface—The cable interface on the Cisco uBR7100 series router must be enabled before the integrated upconverter will output an RF signal.

To configure the integrated upconverter, use the following commands in cable interface configuration mode.

Command
Purpose
ubr7100(config)# interface cable 1/0 

Enter interface configuration mode for the cable interface on the Cisco uBR7100 series router.

ubr7100(config-if)# cable downstream 
frequency down-freq-hz

Enter the fixed center frequency for your downstream RF carrier in Hz. Allowable DOCSIS center frequencies are 91,000,000 to 857,000,000 Hz (the default is 500,000,000 Hz).

ubr7100(config-if)# no cable downstream 
rf-shutdown 

Enable the integrated upconverter.

ubr7100(config-if)# no shutdown 

Enable the cable interface.


Verifying the Integrated Upconverter Configuration

To verify the configuration for the integrated upconverter, enter the show controllers cable downstream command. The following is a typical display with a correctly configured center frequency:

router# show controllers cable1/0 downstream
Cable1/0 Downstream is up
Frequency=525000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 0

Then enter the show controllers cable command, which also displays the center frequency, along with the power levels and whether the integrated upconverter is enabled. The following is a typical display when these values have been correctly configured:

ubr7100# show controllers cable1/0 
Interface Cable1/0
Hardware is IMC11
 BCM3210 revision=0x56B2
 Cable1/0 Upconverter is Enabled Output is Enabled
  Model: 74-2094-01 Serial Number: 0WAV04480010 CLEI Code:      CLEI#
  HW Rev:    PC2D0107 SW Rev: 007, NVRAM Rev: 006 ECI number 123456
  Downstream Frequency 525.0000 MHz
  IF Power 0.3 dBmv  RF Power 51.0 dBmv
...

If the center frequency has not been configured, the frequency is shown as "not set" as shown in the following example:

ubr7100# show controllers cable1/0 downstream
Cable1/0 Downstream is up
Frequency is not set. Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 0

If you are having trouble, make sure the cable connections are not loose or disconnected, and that you have calculated and entered the center frequency for your router accurately.

Setting the Downstream Channel ID

To assign a numeric channel ID to the downstream port on the Cisco cable modem card, use the following command in cable interface configuration mode. Acceptable range is 0 to 255.

CMTS01(config-if)# cable downstream channel-id id


Note The cable downstream channel-id command must be used with the following command:
cable downstream frequency 54000000-1000000000 broadcast frequency - h


The commands are used in instances where you want to send multiple downstream frequencies to a single region that contains CMs that can only connect to upstream ports on the same cable modem card. You must configure unique channel IDs for each downstream that any CM is capable of receiving. The downstream frequency setting must match the setting on the upconverter.


Caution After defining unique downstream IDs, test the CMs for correct operation. Cisco recommends when using this feature that you re-test each subsequent software release of CM code to verify correct operation, and ensure reasonable acquisition time for new installations. Failure to use these commands in conjunction or to test the involved CMs can result in customer service outages of indefinite duration.

Verifying the Downstream Channel ID

To verify the downstream channel ID, enter the show controllers cable command for the downstream port you have just configured. See the following example:

Router# show controllers cable1/0 downstream
Cable1/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 1

For EuroDOCSIS operations, a sample appears below:

Router# show controllers cable 1/0 downstream
Cable1/0 Downstream is up
Frequency 669.0000MHz, Channel Width 8MHz, 64-QAM, Symbol Rate
6.952000 Msps
FEC ITU-T J.83 Annex A, R/S Interleave I=12, J=17
Downstream channel ID: 1

Setting the MPEG Framing Format

The MPEG framing format must be compatible with DOCSIS or EuroDOCSIS specifications and your local cable plant operations.


Tip Annex B is the DOCSIS MPEG framing format standard for North America, supported on the Cisco uBR7111 and Cisco uBR7114 routers. Annex A is the European standard, supported on the Cisco uBR7111E and Cisco uBR7114E routers.



Note Annex A or B framing format is automatically set when configuring the cable interface. The downstream ports and the connected CMs on the network must be set to the same MPEG framing format and support DOCSIS or EuroDOCSIS operations as appropriate.


The following command appears in the Cisco uBR7100 series router configuration file to designate Annex B or Annex A operation. This command sets the downstream MPEG framing format.

CMTS01(config-if)# cable downstream annex {B}

Verifying the Downstream MPEG Framing Format

To verify the downstream MPEG framing format setting, enter the show controllers cable command for the downstream port you have just configured. See the following example:

router# show controllers cable1/0 downstream
Cable1/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 0

A sample output appears below for EuroDOCSIS operations:

Router# show controllers cable 1/0 downstream
Cable3/0 Downstream is up
  Frequency 669.0000MHz, Channel Width 8MHz, 64-QAM, Symbol Rate
  6.952000 Msps
  FEC ITU-T J.83 Annex A, R/S Interleave I=12, J=17
  Downstream channel ID: 0

Setting the Downstream Modulation

To set the downstream modulation, define the speed in symbols per second at which data travels downstream to the subscriber's CM. A symbol is the basic unit of modulation. QPSK encodes 2 bits per symbol, QAM-16 encodes 4 bits per symbol, QAM-64 encodes 6 bits per symbol, and QAM-256 encodes 8 bits per symbol.


Note Setting a downstream modulation rate of QAM-256 requires approximately a 6 dB higher signal-to-noise ratio (SNR) than QAM-64 at the subscriber's cable interface. If your network is marginal or unreliable at QAM-256, use the QAM-64 format instead. Also, consider the significance of your data.


Use the following command in cable interface configuration mode to set the downstream modulation. The standard DOCSIS modulation rate (and the Cisco default) is QAM-64.

CMTS01(config-if)# cable downstream modulation 64qam

Verifying the Downstream Modulation

To verify the downstream modulation setting, enter the show controllers cable command for the downstream port you have just configured. See the following example:

Router# show controllers cable1/0 downstream
Cable1/0 Downstream is up
 Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
 FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected.

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers

5. Verify the downstream carrier is active using the cable downstream if-output command

6. Verify that you have selected the default if you are not certain about the modulation rate needed.

Setting the Downstream Interleave Depth

Set the interleave depth for the downstream port on the Cisco cable modem card. A higher interleave depth provides more protection from bursts of noise on the HFC network; however, it will increase downstream latency.


Note The valid values are 8, 16, 32 (default), 64, and 128.


To set the downstream interleave depth in milliseconds, use the following command in cable interface configuration mode:

CMTS01(config-if)# cable downstream interleave-depth {8|16|32 |64|128}

Verifying the Downstream Interleave Depth

To verify the downstream interleave depth setting, enter the show controllers cable command for the downstream port you have just configured:

Router# show controllers cable1/0 downstream
Cable1/0 Downstream is up
 Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
 FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected.

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers.

5. Verify that the downstream carrier is active using the cable downstream if-output command.

Setting the Downstream Helper Address

Specify an IP address of a DHCP server where UDP broadcast (DHCP) packets will be sent. You can specify a DHCP server for UDP broadcast packets from cable interfaces, and a DHCP server for UDP broadcast packets from hosts.

To set a downstream helper address, use the following commands in cable interface configuration mode.

 
Command
Purpose

Step 1 

CMTS01(config-if)# cable helper-address 10.x.x.x cable-modem

Set the downstream helper address to the DHCP server at IP address 10.x.x.x for UDP broadcast packets from cable modems.

Note Use the IP address of the DHCP server. Both 10.x.x.x and 172.56.x.x are private ranges.

 

Step 2 

CMTS01(config-if)# cable helper-address 172.56.x.x host

Set the downstream helper address to the DHCP server at IP address 172.56.x.x for UDP broadcast packets from hosts.

Verifying the Downstream Helper Address

To verify the downstream helper address setting, enter the show running-config command and look for cable helper-address in the cable interface configuration information:

CMTS01# show running-config
Building configuration...

Current configuration:
!
interface Cable1/0
ip address 10.254.254.254 255.0.0.0
 no ip directed-broadcast
 cable helper-address 192.168.1.1
 no keepalive

Perform these steps if you are having difficulty with verification:

1. Check the cables, upconverters, RF levels, and frequencies if the cable interfaces do not find a downstream signal.

2. Check the cables, RF levels, and upstream frequencies, and enter a no shut command if the cable interfaces find a downstream signal, but not an upstream signal.

3. Check the provisioning servers, ping the DHCP server using the source IP address option—the primary IP address of a cable interface, check IP routing if the cable interfaces acquire an RF upstream and downstream lock, but do not stay up.

4. Check DHCP options and the IP address of the TOD server, ping the TOD server using the source IP address option, check IP routing, verify that the TFTP filename is correct, verify the TFTP file is in the correct directory on the TFTP server, ensure the TFTP file has read privileges, ping the TFTP server using the source IP address option, and check IP routing if the cable interfaces acquire an RF and a DHCP, but fail on TOD or TFTP.

Setting Downstream Rate Limiting

Downstream rate limiting enables you to use the token bucket policing algorithm with traffic shaping options or the weighted discard policing algorithm to buffer, shape, or discard packets that exceed a set bandwidth. Downstream rate limiting is disabled by default.

To enable downstream rate limiting for a downstream port on a Cisco cable modem card, use one of the following commands in cable interface configuration mode.

Command
Purpose

CMTS01(config-if)# cable downstream rate-limit token-bucket



CMTS01(config-if)# cable downstream rate-limit token-bucket shaping

CMTS01(config-if)# cable downstream rate-limit token-bucket shaping granularity 8


CMTS01(config-if)# cable downstream rate-limit token-bucket shaping max-delay 256

Enable rate limiting on the downstream port using the token bucket policing algorithm. With this command, the Cisco uBR7100 series router automatically drops packets that are in violation of the allowable bandwidth.

Enable rate limiting on the downstream port using the token bucket policing algorithm with traffic shaping.


Enable rate limiting on the downstream port using the token bucket policing algorithm with specific traffic shaping time granularity. Acceptable values are 1, 2, 4, 8, or 16 milliseconds.

Enable rate limiting on the downstream port using the token bucket policing algorithm with specific maximum traffic shaping buffering delay. Acceptable values are 128, 256, 512, or 1028 milliseconds.

CMTS01(config-if)# cable downstream rate-limit weighted-discard 3

Enable rate limiting on the downstream port using the weighted packet discard policing algorithm and assign a weight for exponential moving average of loss rate. Acceptable values are 1 to 4.

CMTS01(config-if)# ^Z 
CMTS01

Exit back to EXEC mode so that you can verify the steps.


Verifying Downstream Rate Limiting

To determine if downstream rate limiting is configured and activated, enter the show running-config command and look for the cable interface configuration information. If downstream rate limiting is configured and enabled, a rate limiting entry displays in the output. If downstream rate limiting is disabled, no rate limiting entry displays.

CMTS01# show running-config
Building configuration...

Current configuration:
!
interface Cable1/0
ip address 10.254.254.254 255.0.0.0
 no ip directed-broadcast
 cable helper-address 192.168.1.1
 no keepalive
 cable downstream rate-limit token-bucket shaping
 cable downstream annex B
 cable downstream modulation 64qam

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected.

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers

5. Verify that you selected the default if you are not certain about the modulation rate needed.

6. Verify the downstream carrier is active using the cable downstream if-output command.

Configuring the Upstream Cable Interface

Upstream cable interface commands configure the frequency and input power level of the upstream signal, in addition to error detection and correction of the upstream signal. The configuration of the upstream cable interface depends on the characteristics of your cable plant.

Perform the following tasks to configure the upstream cable interface.


Note For some of these tasks, default values are adequate to configure the device.


"Setting the Upstream Frequency" section

"Setting the Upstream Channel Width" section

"Setting the Upstream Input Power Level" section

"Activating Upstream Admission Control" section

"Activating Upstream Forward Error Correction (FEC)" section

"Specifying Upstream Minislot Size" section

"Activating the Upstream Scrambler" section

"Activating Upstream Differential Encoding" section

"Activating Upstream Rate Limiting" section

"Activating Upstream Frequency Adjustment" section

"Activating Upstream Power Adjustment" section

"Activating Upstream Timing Adjustment" section

"Activating the Upstream Ports" section

"Setting Upstream Backoff Values" section

Setting the Upstream Frequency

The upstream channel frequency of your RF output must be set to comply with the expected input frequency of your Cisco cable modem card. To configure upstream channel frequencies, perform one of the following tasks:

Configure a fixed frequency between 5 to 42 MHz for NTSC operations, then enable the upstream port.

Create a global spectrum group, assign the interface to it, and enable the upstream port.


Note You can also select a default that does not set a specific fixed value.



Note The upstream port is frequency-agile. If you define spectrum groups, the frequency can change while the interface is up and carrying traffic.


A modulation profile consists of a table of physical layer characteristics for the different types of upstream bursts; for example, initial maintenance, long grant, request/data, request, short grant, and station maintenance.


Note The upstream cable interface does not operate until you either set a fixed upstream frequency or create and configure a spectrum group.

If you are setting a fixed upstream frequency, make sure that the frequency selected does not interfere with the frequencies used for any other upstream applications running on the cable plant.


To set a fixed upstream frequency, use the following commands in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable upstream usport 
frequency up-freq-hz

Enter the fixed center frequency for your upstream RF carrier in Hz.

CMTS01(config-if)# no cable upstream 
usport shutdown

Place the upstream port in the "admin up" state.



Tip For NTSC operations, valid ranges are 5000000 to 42000000 Hz.



Caution Some cable systems cannot reliably transport frequencies near these band edges. The wider the upstream channel (in MHz), the more difficulty you might have. Enter a center frequency between 20 and 38 MHz if you have difficulty.


Note You can also select a default that does not set a specific fixed value. The Cisco uBR7100 series software commands the cable interfaces to use this frequency as the center frequency.


Verifying the Upstream Frequency

To verify the current value of the upstream frequency, enter the show controllers cable command for the upstream port you have just configured:

CMTS01# show controllers cable1/0 u0
Cable1/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
  Spectrum Group is overridden
  SNR 33.2560 dB
  Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
  Ranging Backoff automatic (Start 0, End 3)
  Ranging Insertion Interval automatic (60 ms)
  Tx Backoff Start 0, Tx Backoff End 4
  Modulation Profile Group 1
  

Note The upstream frequency displayed in the show controllers cable command output might not match the frequency that you entered when you set the upstream frequency. The Cisco uBR7100 series CMTS might select an upstream frequency close to the frequency you entered that offers better performance. The Cisco uBR7100 series CMTS selects the closest frequency available.


Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers.

5. Verify that you have selected a valid frequency for your router.

Setting the Upstream Channel Width

Enter the channel width in hertz (Hz). For NTSC operations, valid values are 200000 Hz (160 kilosymbols per second [ksps]), 400000 Hz (320 ksps), 800000 Hz (640 ksps), 1600000 Hz (1280 ksps), and 3200000 Hz (2560 ksps). The default is 1600000 Hz.

If no acceptable channels of the specified width are found, the spectrum management card automatically begins to scan the upstream spectrum for the next largest available channel width; for example, if the spectrum management card is unable to find a usable 1.6 MHz upstream channel, it automatically begins searching for usable 800 kHz channels.


Caution Higher symbol rates are more susceptible to RF noise and interference. If you use a symbol rate or modulation format beyond the capabilities of your HFC network, you might experience packet loss or loss of cable interface connectivity.


Note For QAM-16 channel widths of 400 kHz (320 ksps) or greater, Cisco recommends that you use QAM-16 modulation for long and short data, and that you use QPSK for request, initial, and station communications. For QAM-16 channel widths of 200 kHz (160 ksps), all communication must be able to use QAM-16. That is, 160 ksps with QAM-16 requires an exceptional signal-to-noise ratio (SNR) in your upstream channel(s). When you use QAM-16 for request, initial, and station maintenance messages with channel widths greater than 400 kHz, the QAM-16 preamble and message data take longer to transmit than the QPSK format.



Note To set the upstream channel width, use the following commands in cable interface configuration mode.


Command
Purpose
CMTS01(config-if)# cable upstream 
usport channel-width width

Enter the channel width for your upstream RF carrier in Hz.

CMTS01(config-if)# no cable upstream 
usport channel-width

Return the channel width to its default setting of 1600000 Hz.


Verifying Upstream Channel Width

To verify the current value of the upstream channel width, enter the show controllers cable command for the upstream port you just configured. A sample appears below:

CMTS01# show controllers cable1/0 u0
Cable1/0 Upstream 0 is up
  Frequency 24.016 MHz, Channel Width 0.800 MHz, QPSK Symbol Rate 0.640 Msps
  Spectrum Group is overridden
  SNR 33.2560 dB
  Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
  Ranging Backoff automatic (Start 0, End 3)
  Ranging Insertion Interval automatic (60 ms)
  Tx Backoff Start 0, Tx Backoff End 4
  Modulation Profile Group 1

Perform these steps if you are having difficulty with verification:

1. Use a valid combination of modulation format (QPSK/QAM-16), minislot size, frequency, and no shutdown.

2. Use a recommended or previously tested modulation profile. It is not uncommon to create a modulation profile that does not allow cable interface-to-headend communication. Because each message type is individually specified, some messages might not work.

3. Verify using IP ping packets of varying lengths (64 to 1500 bytes). Ping from the headend to the cable interface.

4. Verify with your cable interface vendor that CM software is fully certified or compatible with DOCSIS 1.0 or DOCSIS 1.0 extensions as appropriate.

Setting the Upstream Input Power Level

The Cisco uBR7100 series CMTS controls the output power levels of CMs to meet the desired upstream input power level. The nominal input power level for the upstream RF carrier is specified in decibels per millivolt (dBmV). The default setting of 0 dBmV is the optimal setting for the upstream power level.

The valid range for the input power level depends on the data rate. At 1.6 MHz, the valid range is -10 to 25 dBmV. If your power levels operate at greater than the maximum valid level, use an inline attenuator to bring the power level to within the valid range.


Caution If you increase the input power level, CMs on your HFC network will increase their transmit power level. This increases the carrier-to-noise ratio (C/N) on the network, but also increases distortion products. Composite Second Order Beat (CSO) and Composite Triple Beat (CTB) values worsen by 2 dB for every 1 dB-increased C/N. The return path laser immediately enters a nonlinear mode called clipping and all communication is no longer reliable. Many return lasers send "short" bursts above the clipping thresholds and fail on longer or successive bursts.

You should not adjust your input power level by more than 5 dB in a 30-second interval. If you increase the power level by more than 5 dB within 30 seconds, cable interface service on your network is disrupted. If you decrease the power level by more than 5 dB within 30 seconds, cable interfaces on your network are forced offline.


Note When you run the cable upstream 0 power-level command, Cisco recommends that the adjacent channel not have a large variation. The recommended maximum input power variance is 5 to 6 dBmV.


To set the upstream input power level in dBmV, use the following command in cable interface configuration mode. Default = 0 dBmV.

CMTS01(config-if)# cable upstream usport power-level dbmv

Verifying the Upstream Input Power Level

To verify the current value of the upstream input power level, enter the show controllers cable command for the upstream port you have just configured:

CMTS01# show controllers cable1/0 u0
Cable1/0 Upstream 0 is up
  Frequency 24.016 MHz, Channel Width 0.800 MHz, QPSK Symbol Rate 0.640 Msps
  Spectrum Group is overridden
  SNR 33.2560 dB
  Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
  Ranging Backoff automatic (Start 0, End 3)
  Ranging Insertion Interval automatic (60 ms)
  Tx Backoff Start 0, Tx Backoff End 4
  Modulation Profile Group 1
  

Perform these steps if you are having difficulty with verification:

1. Verify that the upstream amplitude of an optimal RF carrier injected at the fiber node reference input point reaches the cable modem card input point at a consistent level (node-to-node and port-to-port).

2. Verify that this absolute level, as installed, matches both the design and software settings on the Cisco uBR7100 series CMTS.


Note Software adjustments of 1 to 3 dB can be used to adjust for minor variations in measurement or setup and port-to-port calibration differences. These adjustments can significantly improve cable interface performance, especially in marginal situations. Larger adjustments should be made in conjunction with spectrum analyzer-support at the headend or distribution hub.


Activating Upstream Admission Control

The admission control is set as a percentage of the specified upstream channel capacity. The acceptable range is from 10 to 1000 percent. Admission control is disabled by default.

To set the upstream admission control as a percentage of the upstream channel capacity, use the following command in cable interface configuration mode. Valid range is from 10 to 1000 percent.

CMTS01(config-if)# cable upstream usport admission-control percentage

Verifying Upstream Admission Control

To determine if upstream admission control is configured and activated, enter the show running-config command in privileged EXEC mode and look for the cable interface configuration information. If upstream admission control is configured and enabled, an admission control entry displays in the show running-config output, indicating the user-defined percentage of upstream channel capacity allowable. If upstream admission control is disabled, no admission control entry displays in the output.

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers.

5. Verify that you selected a valid frequency for your router.

Activating Upstream Forward Error Correction (FEC)

The Cisco uBR7100 series CMTS uses forward error correction (FEC) to attempt to correct any upstream data that might have been corrupted. FEC is activated by default and should not be disabled. When FEC is activated, all cable modems on the network also activate FEC.


Note Although upstream FEC is an option, Cisco recommends that you use upstream FEC.


To activate the upstream forward error correction and to enable FEC, use the following command in cable interface configuration mode. FEC is enabled by default.

CMTS01(config-if)# cable upstream usport fec

Verifying Upstream FEC

To verify if FEC is activated or deactivated, enter the more system:running-config command and look for the cable interface configuration information. If FEC is enabled, an FEC entry displays in the show running-config output. If FEC is disabled, no FEC entry displays in the output.

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected.

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers.

5. Verify that you selected a valid frequency for your router.

Specifying Upstream Minislot Size

To specify the minislot size (in ticks) for specific upstream cable interfaces, use the following command in cable interface configuration mode. Acceptable values are 2, 4, 8, 16, 32, 64, and 128. Default = 8.

CMTS01(config-if)# cable upstream usport minislot-size size

Verifying Upstream Minislot Size

To verify upstream minislot size, enter the show controllers cable command for the upstream port you have just configured:

CMTS01# show controllers cable1/0 u0
Cable1/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
  Spectrum Group is overridden
  SNR 33.2560 dB
  Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
  Ranging Backoff automatic (Start 0, End 3)
  Ranging Insertion Interval automatic (60 ms)
  Tx Backoff Start 0, Tx Backoff End 4
  Modulation Profile Group 1
  part_id=0xFFFF, rev_id=0xFF, rev2_id=0xFF
  nb_agc_thr=0x0000, nb_agc_nom=0x0000
  Range Load Reg Size=0x58
  Request Load Reg Size=0x0E
  Minislot Size in number of Timebase Ticks is = 8
  Minislot Size in Symbols = 64
  Bandwidth Requests = 0xFE
  Piggyback Requests = 0xD
  Invalid BW Requests= 0x2
  Minislots Requested= 0x2963
  Minislots Granted  = 0x2963
  Minislot Size in Bytes = 16
  Map Advance = 4000 usecs
  UCD Count = 32964
  DES Ctrl Reg#0 = C000C043, Reg#1 = 0

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected.

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers.

5. Verify that you selected a valid frequency for your router.

Activating the Upstream Scrambler

The scrambler on the upstream RF carrier enables cable modems on the HFC network to use built-in scrambler circuitry for upstream data transmissions. The scrambler circuitry improves reliability of the upstream receiver on the cable modem card.


Caution The upstream scrambler is activated by default and should not be disabled under normal circumstances. Disabling it can result in corrupted packets. Disable it only for prototype modems that do not support the upstream scrambler.

To activate the upstream scrambler, use the following command in cable interface configuration mode. The upstream scrambler is enabled by default.

CMTS01(config-if)# cable upstream usport scrambler

Verifying the Upstream Scrambler

To determine if the upstream scrambler is activated, enter the more system:running-config command and look for the cable interface configuration information.

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected.

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers.

5. Verify that you selected a valid frequency for your router.

Activating Upstream Differential Encoding

To enable differential encoding on upstream traffic to a specified cable interface, use the following command in cable interface configuration mode. Upstream differential encoding is enabled by default.

CMTS01(config-if)# cable upstream usport differential-encoding

Verifying Upstream Differential Encoding

To determine if upstream differential encoding is activated, enter the show running-config command and look for the cable interface configuration information. If upstream differential encoding is enabled, a differential encoding entry displays in the show running-config output. If upstream differential encoding is disabled, no differential encoding entry displays in the output.

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected.

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers.

5. Verify that you selected a valid frequency for your router.

Activating Upstream Rate Limiting

Upstream rate limiting allows upstream bandwidth requests from rate-exceeding cable modems to be buffered without incurring TCP-related timeouts and retransmits. This enables the CMTS to enforce the peak upstream rate for each cable modem without degrading overall TCP performance for the subscriber CPEs. Upstream grant shaping is per cable interface (SID).

Token bucket policing with shaping is the per-upstream default rate-limiting setting at the CMTS. Shaping can be enabled or disabled for the token-bucket algorithm.

To enable upstream rate limiting for an upstream port on a Cisco cable modem card, use one of the following commands in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable upstream usport 
rate-limit  
 
 
CMTS01(config-if)# cable upstream usport 
rate-limit token-bucket 
 
 
 
 
 
CMTS01(config-if)# cable upstream usport 
rate-limit token-bucket shaping 

Enable rate limiting for the specified upstream cable interface.

Enable rate limiting for the upstream cable interface employing the token bucket policing algorithm. With this command the Cisco uBR7100 series CMTS automatically drops packets in violation of allowable upstream bandwidth.

Default. Enable rate limiting for the upstream cable interface employing the token bucket policing algorithm with traffic shaping.

CMTS01(config-if)# ^Z 
CMTS01

Exit back to the EXEC mode so that you can verify upstream rate limiting.


To disable upstream traffic shaping for an upstream port, enter the following command in cable interface configuration mode:

CMTS01(config-if)# no cable upstream usport rate-limit

Verifying Upstream Rate Limiting

To determine if upstream rate limiting is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream rate limiting is configured and enabled, a rate limiting entry displays in the show running-config output. If upstream rate limiting is disabled, no cable upstream rate-limit displays in the output.

You can also perform the following tasks to verify that rate limiting is enabled on the upstream channel:


Step 1 Configure a low-peak upstream rate limit for the cable modem in its QoS profile. Either use the command line interface to modify the modem's QoS profile, or edit the modem's TFTP config file.

Step 2 Use a regular rate-limiting algorithm on the upstream without rate shaping and note the drops of the excess bandwidth requests from this cable modem when it exceeds its peak upstream rate.

Use the show interface cx/y sid counters command to see the bandwidth request drops. Verify that the upstream rate received by that modem is less than its configured peak rate due to the timeouts and backoffs produced by the drop in bandwidth requests. Enter the show interface cx/y sid command to see the input rate at CMTS in bps.

Step 3 Enable grant shaping on the upstream channel by using the new shaping keyword extension to the token-bucket algorithm CLI command.

Step 4 Make the cable modem exceed its peak upstream rate by generating upstream traffic, and note the effect of grant buffering (shaping) at the CMTS. If you use cable modem-to-CMTS pings, you will see a perceivable slowing down of the pings.

Let the pings run for a period to let averages at the CMTS settle; then view the upstream rate received by this single modem. Use the show interface cx/y command and see the input rate in bps. This value should be close to the modem's peak upstream rate. Also note the drop counts for the modem's SID by using the show interface sid counters command and verify that the CMTS no longer drops the bandwidth requests from the cable modem.

The bandwidth request drop count (from previous non-shaping test) remains unchanged when upstream rate shaping is used, indicating that the CMTS is actually shaping (buffering) the grants for the modem. Verify that the input rate at the CMTS (from the single rate-exceeded CM) stabilizes close to the configured peak rate of 128 Kbps.


Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected.

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers.

5. Verify that you selected a valid frequency for your router.

Activating Upstream Frequency Adjustment

To enable automatic upstream frequency adjustment for a specified cable interface, use the following commands in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable upstream 
usport frequency-adjust averaging 
percentage

Set the minimum number of frequency adjustment packets required to justify changing the upstream frequency adjustment method as a percentage. Acceptable range is 10 to 100 percent.
Default = 30 percent.

CMTS01(config-if)# end  
CMTS01#

Return to enable (privileged EXEC) mode.


To return the automatic upstream frequency adjustment percentage to the default value of 30 percent, enter the following command in cable interface configuration mode:

CMTS01(config-if)# no cable upstream usport frequency-adjust averaging

Verifying Upstream Frequency Adjustment

To determine if upstream frequency adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream frequency adjustment is enabled, frequency adjustment entries are displayed in the show running-config output. If frequency adjustments are disabled, no frequency adjustment entry displays in the output.

Perform these steps if you are having difficulty with verification:

1. Ensure the cable connections are not loose or disconnected

2. Ensure the cable modem card is firmly seated in its chassis slot.

3. Ensure the captive installation screws are tight.

4. Verify that you have entered the correct slot and port numbers; you selected a valid frequency for your router.

Activating Upstream Power Adjustment

To enable upstream power adjustment for a specified cable interface, use one of the following commands in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable upstream usport 
power-adjust continue db  

Set the minimum power adjustment in dB that allows continued ranging status. Valid values are 2 to 15 dB. Default = 2 dB.

CMTS01(config-if)# cable upstream usport 
power-adjust noise percentage 

Set the minimum number (percentage) of power adjustment packets required to justify changing the upstream power rating. Valid values are 10 to 100 percent. Default = 30 percent.

CMTS01(config-if)# cable upstream 0 power-adjust 
threshold db

Set the power adjustment threshold in dB. Valid values are 0 to 2 dB. Default = 1 dB.

CMTS01(config-if)# end  
CMTS01#

Return to enable (privileged EXEC) mode.


To return the automatic upstream power adjustment ranging value to the default of 2 dB, enter the following command in cable interface configuration mode:

CMTS01(config-if)# no cable upstream usport power-adjust continue 

To return the automatic upstream power adjustment noise value to the default of 30 percent, enter the following command in cable interface configuration mode:

CMTS01(config-if)# no cable upstream usport power-adjust noise

To return the upstream power adjustment threshold value to the default of 1 dB, enter the following command in cable interface configuration mode:

CMTS01(config-if)# no cable upstream usport power-adjust threshold

Verifying Upstream Power Adjustment

To determine if upstream power adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream power adjustment is enabled, any or all three of the continue, noise, and threshold power adjustment entries are displayed in the show running-config output. If all three continue, noise, and threshold upstream power adjustments are disabled, no power adjustment entry displays in the show running-config output.

Activating Upstream Timing Adjustment

To enable upstream timing adjustment for a specified cable interface, use one of the following commands in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable upstream usport 
time-adjust continue seconds 

Set the minimum timing adjustment that allows continued ranging status. Valid values are 2 to 64 seconds. Default = 2 seconds.

CMTS01(config-if)# cable upstream usport 
time-adjust threshold seconds 

Set the timing adjustment threshold value in seconds. Valid values are 1 to 32 seconds. Default = 1 second.

CMTS01(config-if)# end  
CMTS01#

Return to enable (privileged EXEC) mode.


To return the upstream time adjustment ranging value to the default of 2 seconds, enter the following command in cable interface configuration mode:

CMTS01(config-if)# no cable upstream usport time-adjust continue

To return the upstream time adjustment threshold value to the default of 1 second, enter the following command in cable interface configuration mode:

CMTS01(config-if)# no cable upstream usport time-adjust threshold

Verifying Upstream Timing Adjustment

To determine if upstream timing adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream timing adjustment is enabled, either or both of the continue and threshold timing adjustment entries are displayed in the show running-config output. If both the continue and threshold upstream timing adjustments are disabled, no timing adjustment entry displays in the show running-config output.


Tip If you are having difficulty with verification, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers.


Activating the Upstream Ports

Each upstream port must be activated to enable upstream data transmission from the cable modems on the HFC network to the Cisco uBR7100 series CMTS.


Note The upstream cable interface does not operate until you either set a fixed upstream frequency or create and configure a spectrum group. Refer to the "Setting the Upstream Frequency" section, or the "Creating Spectrum Groups" section for details.


To activate the upstream ports, use the following commands in global configuration mode.

Command
Purpose
CMTS01(config)# interface cable slot/port

Specify a cable interface and enter cable interface configuration mode.

CMTS01(config-if)# no cable upstream 
usport shutdown

Enable upstream data traffic.


Verifying the Upstream Ports

To determine if the upstream ports are activated or deactivated, enter the show interface cable command for the upstream port just configured:

router# show interface cable1/0
Cable1/0 is up, line protocol is up
 Hardware is BCM3210 FPGA, address is 00e0.1e5f.7a60 (bia 00e0.1e5f.7a60)
 Internet address is 1.1.1.3/24
 MTU 1500 bytes, BW 27000 Kbit, DLY 1000 usec, rely 255/255, load 1/255
 Encapsulation, loopback not set, keepalive not set
 ARP type: ARPA, ARP Timeout 04:00:00
 Last input 00:00:25, output 00:00:00, output hang never
 Last clearing of "show interface" counters never
 Queuing strategy: fifo
 Output queue 0/40, 0 drops; input queue 0/75, 0 drops
 5 minute input rate 0 bits/sea, 0 packets/sec
 5 minute output rate 0 bits/sec, 0 packets/sec
     10878 packets input, 853740 bytes, 0 no buffer
     Received 3679 broadcasts, 0 runts, 0 giants, 0 throttles
     3 input errors, 3 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     5401 packets output, 645885 bytes, 0 underruns
     0 output errors, 0 collisions, 9 interface resets
     0 output buffer failures, 0 output buffers swapped out

Setting Upstream Backoff Values

The DOCSIS-specified method of contention resolution for cable modems wanting to transmit data or requests on the upstream channel is a truncated binary exponential backoff, with the initial backoff window and the maximum backoff window controlled by the CMTS. The Cisco uBR7100 series CMTS specifies backoff window values for both data and initial ranging, and sends these values downstream as part of the Bandwidth Allocation Map (MAP) MAC message.

The values are configurable on the Cisco uBR7100 series software and are power-of-two values. For example, a value of 4 indicates a window between 0 and 15; a value of 10 indicates a window between 0 and 1023. You can set fixed start and end values for data backoff on the upstream ports, or you can set the upstream ports for automatic data backoff. You have the same options for ranging backoff. For both backoff windows, the default start value is 0; the default end value is 4. Valid values are from 0 to 15.


Note Cisco does not recommend you adjust default values, but enable the automatic dynamic backoff algorithm. Refer to the "Configuring Dynamic Contention Algorithms (Cable Insertion Interval, Range, and Data Backoffs)" section on page 5-4.


To set data or ranging backoff values for an upstream port, use one or more of the following commands, in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable upstream 
usport data-backoff start end  
 
 
or 
 
CMTS01(config-if)# cable upstream 
usport data-backoff automatic

The automatic setting is optimized for as many as 250 cable interfaces per upstream port. Set manual values for data backoff windows only when operating with more than 250 cable interfaces per upstream port.

This command configures the default backoff window values of 0 and 4.

CMTS01(config-if)# cable upstream 
usport range start end  
 
 
or 
 
CMTS01(config-if)# cable upstream 
usport range automatic

The automatic setting is optimized for as many as 250 cable interfaces per upstream port. Set manual values for data backoff windows only when operating with more than 250 cable interfaces per upstream port.

This command configures the default backoff window values of 0 and 4.


When considering whether to adjust backoff values, keep the following in mind:

The cable interface reconnection time after a power outage is related to the following factors:

DHCP, TOD, and TFTP server capacity. These servers often operate well below 1% load under normal situations, but can jump to over 100% after an outage.

Adjusting the backoffs to larger numbers slows cable interface reconnection and reduces server load.

Backoffs which are too small result in cable interfaces failing to range the upstream RF levels correctly and cycling to maximum power, thus increasing connection time and reducing network performance.

Backoffs which are too large result in increased recovery time after a large service outage.

There is significant variation in cable interface performance (brand to brand) in cable interface restart time.

All cable interfaces should recover between approximately 0 to 10 minutes after all services are restored (Cisco uBR7100 series, RF transport, DHCP/TFTP/TOD servers). Cable modems taking longer than 10 minutes could indicate a problem in the cable modem, in CMTS settings, or in the DOCSIS provisioning servers.


Note Upstream segments serving a relatively large number of cable interfaces (for example, more than 1600) might suffer recovery times greater than 10 minutes.


Verifying Upstream Data Backoff Automatic

To verify backoff window settings, enter the show controllers cable command for the upstream port you have just configured:

CMTS01# show controllers cable1/0 u0
Cable1/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
  Spectrum Group is overridden
  SNR 33.2560 dB
  Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
  Ranging Backoff automatic (Start 0, End 3)
  Ranging Insertion Interval automatic (60 ms)
  Tx Backoff Start 0, Tx Backoff End 4
  Modulation Profile Group 1
  part_id=0x3137, rev_id=0x03, rev2_id=0xFF
  nb_agc_thr=0x0000, nb_agc_nom=0x0000
  Range Load Reg Size=0x58
  Request Load Reg Size=0x0E
  Minislot Size in number of Timebase Ticks is = 8
  Minislot Size in Symbols = 64
  Bandwidth Requests = 0xFE
  Piggyback Requests = 0xD
  Invalid BW Requests= 0x2
  Minislots Requested= 0x2963
  Minislots Granted  = 0x2963
  Minislot Size in Bytes = 16
  Map Advance = 4000 usecs
  UCD Count = 32964
  DES Ctrl Reg#0 = C000C043, Reg#1 = 0

Enabling and Configuring Baseline Privacy

Introduction to the Baseline Privacy Interface (BPI)

BPI gives subscribers data privacy across the RF network, encrypting traffic flows between the CMTS and CM. The level of data privacy is roughly equivalent to that provided by dedicated line network access services such as analog modems or digital subscriber lines (DSL). BPI provides basic protection of service, ensuring that a CM, uniquely identified by its MAC address, can obtain keying material for services only it is authorized to access.


Note Encryption/decryption is subject to export licensing controls.



Note Because DOCSIS 1.0 BPI does not authenticate CMs, it does not protect against users employing cloned CMs, masquerading as authorized CMs. Specific Cisco IOS releases provide protection against spoofing, and support commands that can be used to configure source IP filtering on RF subnets to prevent a user from using a source IP address that is not valid for the connected IP subnet.


BPI is defined as a set of extended services within the DOCSIS MAC sublayer. Refer to the DOCSIS Baseline Privacy Interface Specification for detailed requirements.

BPI extends the definition of the MAC sublayer's SID. The DOCSIS RF Interface Specification defines a SID as a mapping between CMTS and CM to allocate upstream bandwidth and class of service management. When BPI is activated, the SID also identifies a particular security association and has upstream and downstream significance. When BPI is operational, downstream multicast traffic flow that typically does not have a SID associated with it, now has a SID. The Privacy Extended Header Element includes the SID associated with the MAC Packet Data Physical Data Unit (PDU). The SID and other components of the extended header element identify to a CM the keying material required to decrypt the MAC PDU's packet data field.

BPI's key management protocol runs between the CMTS and the CM. CMs use the protocol to obtain authorization and traffic keying material relevant to a particular SID from the CMTS, and to support periodic reauthorization and key refresh.

The key management protocol uses RSA—a public key encryption algorithm—and the electronic codebook (ECB) mode of DES to secure key exchanges between the CMTS and a CM. Privacy is in the form of 56-bit (the default) or 40-bit encryption between the CMTS and CM. Since BPI is part of DOCSIS, all DOCSIS-certified CMs and qualified CMTS are fully interoperable. Figure 3-1 shows a BPI architecture.


Note CMs must have factory-installed RSA private/public key pairs to support internal algorithms to generate key pairs prior to first BPI establishment.


A SID's keying material has a limited life span. When the CMTS delivers SID keying material to a CM, it also provides the CM with the lifetime value.

Figure 3-1 BPI Network Example

BPI Key Management

BPI initialization begins with the CM sending the CMTS an authorization request, containing data identifying:

CM—48-bit IEEE MAC address

CM's RSA public key

List of zero or more assigned unicast SIDs that have been configured to run BPI

At that time, BPI provides basic protection against theft of service by ensuring the CM, identified by its MAC address, can obtain keying materials only it is authorized to access. The CMTS replies with a list of SIDs on which to run BPI. The reply also includes an authorization key from which the CM and CMTS derive the keys needed to secure a CM's subsequent requests for additional encryption keys. After obtaining the traffic encryption key, the CMs begin to transmit encrypted data.

Differentiating Traffic Streams

BPI only encrypts data on the cable network and only encrypts the user data itself, not cable MAC headers. BPI also does not encrypt MAC management messages.

After BPI is enabled, however, and encryption has been negotiated for a given SID, all user data sent using that SID is encrypted. BPI differentiates traffic, based on the SID alone.

CM Communication with BPI

Figure 3-2 illustrates BPI communications. When user A sends packets to user B, the CM encrypts those packets using special keys specific to the user's CM. Packets are then transmitted to the CMTS where they are decrypted.

If user B is attached to the cable TV network, the CMTS then re-encrypts the information using a key specific to user B, and the encrypted data is passed to user B's CM where it is decrypted and sent to user B. In this manner, an unauthorized user is not able to see unencrypted traffic between user A and user B.


Caution Since BPI occurs only on the cable TV network, however, all traffic going upstream is decrypted as it passes the CMTS. If user A is attempting to communicate with someone beyond the cable network—user C—all traffic beyond the CMTS is not encrypted.

Figure 3-2 BPI Encrypted Data on the Cable TV Network

Enabling BPI

To enable BPI, choose software images at both the CMTS and CM that support the mode of operation. For the Cisco uBR7100 series software, choose an image with "k1" in its file name or BPI in the feature set description. For Cisco uBR924 cable access routers, all CM images from Cisco IOS Release 12.0(5)T1 or later support this by default. For earlier Cisco IOS release CM images, choose an image with "k1" in its file name or BPI in the feature set description.


Note For the CMTS, BPI is enabled by default when you select an image that supports BPI. For CMs, enable BPI using the DOCSIS configuration file using the instructions that follow in this section.


When baseline privacy is enabled, the Cisco uBR7100 series router generates traffic encryption keys (TEKs) for each applicable SID; 56-bit encryption/decryption is the default for Cisco uBR7100 series equipment.

The router uses the keys to encrypt downstream data and decrypt upstream traffic from two-way cable interfaces. The Cisco uBR7100 series router generates keys for unicast, broadcast, and multicast operation as appropriate. Keys are refreshed periodically and have a default lifetime of 12 hours.

Configuring Baseline Privacy


Note Both the CMTS and the CM must support baseline privacy and have BPI enabled.


To configure baseline privacy (deviating from default values), follow procedures in this section:

"Configuring Key Encryption Key (KEK) Privacy" section

"Configuring Traffic Encryption Key (TEK) Privacy" section

"Activating Baseline Privacy" section

Configuring Key Encryption Key (KEK) Privacy

A lifetime KEK can be set from 86400 to 6048000 seconds. If you do not set a KEK value, the default values are used.

To configure KEK data privacy on the HFC network, enter one of the following commands in cable interface configuration mode.

Command
Purpose

CMTS01(config-if)# cable privacy kek life-time seconds

Set the cable privacy KEK lifetime in seconds. Valid values are from 86400 to 6048000 seconds.
Default = 604800.

Verifying KEK Privacy

To verify the KEK lifetime values that are set, enter the show cable privacy kek command:

CMTS01# show cable privacy kek
Configured KEK life time value = 750000

Tip If you are having difficulty with verification, make sure you have entered a valid value for lifetime.


Configuring Traffic Encryption Key (TEK) Privacy

A lifetime TEK can be set from 1800 to 604800 seconds. If you do not set a TEK value, the defaults are used.

To configure TEK data privacy on the HFC network, use the following commands in cable interface configuration mode.

Command
Purpose

CMTS01(config-if)# cable privacy tek life-time seconds

Set the cable privacy TEK life time in seconds. Valid values are from 1800 to 604800 seconds.
Default = 43200 seconds.

Verifying TEK Privacy

To verify the TEK lifetime values that are set, enter the show cable privacy tek command:

CMTS01# show cable privacy tek
Configured TEK life time value = 56000

Activating Baseline Privacy

BPI is activated by default when using an image that supports baseline privacy. Commands in the cable interface configuration mode are as follows:

Command
Purpose
CMTS01(config-if)# cable privacy enable

Activate cable privacy. This is the default.

CMTS01(config-if)# cable privacy mandatory

Activate cable privacy and do not allow access for any unencrypted cable modem connections.


Verifying Baseline Privacy

To determine if baseline privacy is activated, enter the show interface privacy command. When using a Cisco uBR7100 series "k1" image, cable privacy is enabled by default and can only be disabled with the no cable privacy command. The cable modem must also be configured to support baseline privacy.


Tip If you are having difficulty with verification, make sure you entered a valid value for lifetime for KEK and TEK privacy.



Note If you entered the cable privacy mandatory command, then cable interfaces do not operate unless the cable interface configuration file specifies that privacy is on.


Configuring and Activating Frequency Agility

Set upstream port frequency to a fixed value during system installation and testing. Choose this value from your frequency allocation plan for the RF plant segment connected to the upstream.

When the system has reached sufficient stability, the RF domain topology can be entered into the configuration file to enable spectrum management. Spectrum management or frequency agility is configured and activated using spectrum groups.

Frequency-hopping policies supported on all Cisco cable modem cards include combined blind and scheduled specifications, as well as guided frequency hops.


Note The cable interface will not operate until you either create and configure a spectrum group or set a fixed upstream frequency. From the interface configuration prompt, an interface is assigned membership in a spectrum group. From the interface point of view, the spectrum group also represents the set of upstreams connected to the same group of fiber nodes. This allows the spectrum manager to know if upstream frequencies need to be managed together.


To configure and activate frequency agility, perform the following tasks:

"Creating Spectrum Groups" section

"Configuring and Activating Spectrum Groups" section

"Configuring Spectrum Group Characteristics" section

Creating Spectrum Groups

To create a spectrum group, use one of the following general commands in global configuration mode.

Command
Purpose
CMTS01(config)# cable spectrum-group 
group-number type scheduled daily

Create a scheduled spectrum group that can change its frequency and power level at the same time every day.

CMTS01(config)# cable spectrum-group 
group-number type scheduled periodic-sec seconds

Create a scheduled spectrum group that can change its frequency and power level at a specified interval in seconds.


Frequency agility is configured and activated using spectrum groups. You can create from 1 to 32 spectrum groups for each cable interface card upstream port.

To create spectrum groups, specify a list of upstream frequencies and nominal power levels that each spectrum group can use when an upstream frequency change is necessary. Each spectrum group should have its own list of upstream frequencies.

After you have created one or more spectrum groups, you can add characteristics to them, providing more definitive control over frequency usage and frequency hopping. See the "Configuring and Activating Spectrum Groups" section.

Verifying Spectrum Groups

To verify that a spectrum group is created, enter the show cable spectrum-group command:

CMTS01# show cable spectrum-group
spectrum-group 1
spectrum-group 2
spectrum-group 3

Tip If you are having difficulty with verification, make sure you have entered a valid spectrum group number and type.


Configuring and Activating Spectrum Groups

After you create a spectrum group, configure a list of upstream frequencies and optional nominal power levels that each spectrum group can use when an upstream frequency change is necessary. Each spectrum group should have its own list of upstream frequencies.


Note Valid frequencies are 5,000,000 to 42,000,000 Hz for NTSC operations and 5,000,000 to 65,000,000 for EuroDOCSIS 8 MHz operations.


To configure and activate a spectrum group, use the following commands in global configuration mode.

Command
Purpose
CMTS01(config)# cable spectrum-group 
group-number [time day hh:mm:ss] [delete] 
frequency ctr-freq-hz [power-level-dbmv] 
 
 
 
 
 
 
 
 
 
CMTS01(config)# cable spectrum-group 
group-number [time day hh:mm:ss] [delete] band 
start-freq-hz end-freq-hz [power-level-dbmv]

Add the upstream frequency to the list of valid frequencies with a default power level for a spectrum group.

Note If the time parameter is configured, the frequency setting or band is either made available or deleted at the specified time.

The power level value should only be changed if you want to change the power level as part of spectrum management. The standard power level is 0 dBmV.



Note Configuring a spectrum group enables frequency agility and disables the fixed upstream frequency setting.



Tip You must repeat one of the previous command for each frequency or power level that you want to add to a spectrum group's list of valid values.


If your cable plant has an upstream noise characteristic on a weekly cycle, use time-scheduled spectrum allocation:

CMTS01(config)# cable spectrum-group 1 time Mon 08:00:00 frequency 21600000

Deletion is performed using the delete keyword:

CMTS01(config)# cable spectrum-group 1 time Mon 18:00:00 delete frequency 21600000

The following example displays a spectrum group configuration that is designed to perform minor equalization as a function of frequency.

CMTS01(config)# cable spectrum-group 1 frequency 21600000
CMTS01(config)# cable spectrum-group 1 frequency 24800000 1
CMTS01(config)# cable spectrum-group 1 frequency 28000000 2

In the previous example, the upstream port nominal receive power at 21.6 MHz is 0 dBmV, at 24.8 MHz is 1 dBmV, and at 28.0 MHz is 2 dBmV. At any time, the power level set in the interface configuration overrides the spectrum group power level.

The following example enables spectrum management for all upstream ports, assuming that all combiner groups use the frequency band from 20 to 26 MHz:

CMTS01(config)# cable spectrum-group 1 band 20000000 26000000
CMTS01(config)# cable spectrum-group 2 shared
CMTS01(config)# cable spectrum-group 2 band 20000000 26000000
CMTS01(config)# cable spectrum-group 3 shared
CMTS01(config)# cable spectrum-group 3 band 20000000 26000000
CMTS01(config)# interface Cable1/0
CMTS01(config-if)# cable spectrum-group 1
CMTS01(config-if)# cable upstream 2 spectrum-group 2
CMTS01(config-if)# cable upstream 3 spectrum-group 2
CMTS01(config-if)# exit

For the 20 to 26 MHz band of each RF domain, the spectrum is channelized according to the channel width settings of each member port. For example, if the ports U2 and U3 of Cable1/0 are set to 3.2 MHz and 1.6 MHz channel widths, respectively, then spectrum group 2 uses the following channelization:


> Channel Width Start Stop Center
>           (Mhz) (Mhz) (Mhz) (Mhz)
> 1        3.2    20.0 23.2 21.6
> 2*       1.6    20.0 21.6 20.8
> 3*       1.6    21.6 23.2 22.4
> 4        1.6    23.2 24.8 24.0

Note Channels 2 and 3 are not available when channel 1 is in use.


Because the group is shared, ports U2 and U3 will be assigned channels 1 and 4, respectively, to prevent overlap.


Note There are no alternate frequency assignments for either port and bandwidth is wasted from 24.8 to 26.0 MHz. To create alternate channels, increase the upper boundary from 26.0 to 28.0 MHz.


> Channel  Width  Start Stop  Center
>           (Mhz)  (Mhz) (Mhz) (Mhz)
>  1        3.2    20.0  23.2  21.6
>  2        3.2    23.2  26.4  24.8
>  3        1.6    20.0  21.6  20.8
>  4        1.6    21.6  23.2  22.4
>  5        1.6    23.2  24.8  24.0
>  6        1.6    24.8  26.4  25.6
>  7        1.6    26.4  28.0  27.4

Care should be taken to reduce the spectrum allocation when used with small channel widths. Otherwise, there will be a large number of upstream channel slots.

For example, if the allocation is from 20.0-to-28.0 MHz and an upstream port has its channel width set to 0.2 MHz, there are 40 possible slots for that channel width. Blind frequency hopping can require a long time to find the clean slot, because it tries each available slot, one at a time for several seconds during each try.

Verifying Spectrum Group Configuration

To verify if spectrum groups are configured and activated, enter the show cable spectrum-group command:

CMTS01# show cable spectrum-group
22:07:46: %SYS-5-CONFIG_I: Configured from console by console
Group  Frequency      Upstream     Weekly Scheduled            Power   Shared
No.    Band           Port         Availability                Level   Spectrum
       (Mhz)                       From Time:    To Time:      (dBmV)
1       5.000-15.000                                           0       Yes
1      12.000                                                  0       Yes
1      22.000                                                  7       Yes
2      29.000                                                  6       No
2      26.000                                                  0       No
3      35.000-41.000                                           0       No
3      16.000-19.000                                           5       No
5*      5.000-10.000               Thu 21:50:00  Thu 21:45:00  0       Yes 

Verifying Frequency Hopping

To verify frequency hopping on the Cisco uBR7100 series CMTS, note the following:

The controller must report being up.

The comparison of the number of errors versus the number of error-free packets is a measure of the link quality. The percentage of errors should be less than 1%.

After you have established basic operation, inject a tone to the upstream port. For example, if the upstream frequency is currently 22.4 MHz, inject a 22.4 MHz tone at approximately the same power level as the modem. If the power level at the modem is 40 dBmV, set the tone power to 40 dBmV. The interfering carrier should shut down the channel and cause the frequency to change to the next configured value. In this example, it would be 24.0 MHz.

If you do not have an RF tone generator, use another cable modem card and modem that carries traffic. Connect the upstream to the same combiner group, and use the data carrier as an interfering signal by setting it to the same frequency. For example, to test frequency hopping on c1/0, install c1/0 and connect both upstreams together using a combiner. If the upstream frequency of c1/0 is currently 22.4 Mhz, set c1/0 to 22.4 MHz while c1/0 is carrying traffic. This should force c1/0 to change the frequency to the next configured value.


Tip If you are having difficulty with verification, make sure you entered a valid spectrum group number, time, frequency, and input power level.

When defining your spectrum, avoid frequencies with known ingress problems such as amateur radio bands or short-wave bands and spectrum below 20 MHz; allow extra bands for frequency hopping; place upstream ports in the same combiner group in a shared spectrum group; use the receive power level setting to perform slight equalization adjustments.


Configuring Spectrum Group Characteristics

After you have created one or more spectrum groups, add characteristics to them. As stated in the DOCSIS RFI specification, RF channel migration occurs by broadcasting a change in the upstream channel descriptor (UCD) message to all cable interfaces. The UCD message contains the upstream frequency and transmission parameters associated with an upstream channel.

The speed of channel migration via the UCD message is typically less than 20 milliseconds (ms). During this time, upstream transmission is interrupted until the cable interface transmitter adjusts to its new frequency. Data is stored in the cable interface's buffers during this time and is sent when the frequency hop is complete.

Also, per the DOCSIS RFI, station maintenance intervals are used to perform per-modem keepalive polling. The Cisco uBR7100 series poll each cable interface. When ingress noise causes loss of keepalive messages from a configurable percentage of all cable interfaces, resulting in those cable modems going offline, a new frequency is selected from the allocation table and a UCD update is performed.


Note Also see the "Polling Cable Modems" section on page 5-15.


The migration time is 10 seconds (maximum) for the decision and 20 ms for the frequency hop. The percentage threshold method prevents a single failing cable interface from affecting service to other good cable interfaces. The system will not hop endlessly because one cable interface is generating 90% of the errors and 90% of the traffic.

The minimum period between frequency hops is also configurable, with a default setting of 300 seconds. If the destination channel is expected to be impaired, the minimum period between frequency hops can be reduced to a small value such as 10 seconds. This allows the frequency hop to continue more rapidly until a clear channel is found. If excessive frequency hop is an issue, the minimum period between hops can be increased.

To adjust the frequency hop threshold percentage or the minimum period between frequency hops, use the following commands in global configuration mode.

Command
Purpose
CMTS01(config)# cable spectrum-group 
groupnum hop threshold percent

Set the percentage of all cable modems losing keepalive messages (going offline) that will cause a frequency hop.

CMTS01(config)# cable spectrum-group 
groupnum hop period seconds

Set the minimum time between frequency hops in seconds. Valid values are from 1 to 3600 seconds.


To specify that a particular spectrum group is a shared RF spectrum group, use the following command in global configuration mode.

Command
Purpose
CMTS01(config)# cable spectrum-group 
groupnum shared

Specifying a given spectrum group as "shared" tells the Cisco uBR7100 series CMTS that you want to be sure that upstream frequencies assigned to upstream interfaces are not assigned to additional upstream interfaces.


Table 3-1 describes the spectrum-group parameters.

Table 3-1 spectrum-group parameters

Syntax
Valid Values
group number

Specifies the spectrum group for which you are specifying a parameter value or specifies the number of the spectrum group you wish to remove from your router configuration. Valid range is from 1 to 32.

parameter

The spectrum group values that can be changed or added are:

Frequency—Specifies the center frequency for the given spectrum group. Entering additional
cable spectrum-group group number frequency commands for the same spectrum group creates a collection of allowable center frequencies for spectrum group hopping.

Band—Specifies a range of center frequencies the Cisco uBR7100 series router can scan in order to find an acceptable channel to which the spectrum group can hop.

Time—Specifies a time of day that the Cisco uBR7100 series router should automatically perform a frequency hop for the given upstream spectrum group.

Note The time command can be combined with the frequency and band commands.

Hop period—Specifies the minimum period (in seconds) before which a frequency hop can occur.

Hop threshold—The threshold value (expressed as a percentage) of the number of "offline" modems identified before the Cisco uBR7100 series router initiates an automatic frequency hop.

Shared—Specifies that a particular spectrum group is a shared RF spectrum group; upstream frequencies assigned to upstream interfaces are not to be assigned to additional upstream interfaces.

value

The corresponding parameter value for the parameter you are defining for a given spectrum group.


Examples are provided to configure differing spectrum groups:

Use the following example to configure spectrum group 1 with an upstream frequency of 6,500,000 Hz and a default power level of 0 dBmV:

Router(config)# cable spectrum-group 1 frequency 6500000

Use the following example to add the upstream frequency 7,000,000 Hz to the list of valid frequencies with a default power level of 0 dBmV for spectrum group 1:

Router(config)# cable spectrum-group 1 frequency 7000000

Use the following example to configure spectrum group 2 with an upstream frequency 7,500,000 Hz and change the power level to 5 dBmV:

Router(config)# cable spectrum-group 2 frequency 7500000 5

Use the following example to configure spectrum group 3 with an upstream band of 12,000,000 to 18,000,000 Hz and default power level of 0 dBmV:

Router(config)# cable spectrum-group 3 band 12000000 18000000

Use the following example to add the upstream band 20,000,000 to 24,000,000 Hz to the list of valid bands with a change in the power level of 13 dBmV for spectrum group 3:

Router(config)# cable spectrum-group 3 band 20000000 24000000 13

Use the following example to configure a continuous band between 5,000,004 and 40,000,000 Hz for scheduled spectrum group 4 with a default power level of 0 dBmV. The spectrum group will be available to the spectrum group starting at 12:00 p.m. local time each Monday:

Router(config)# cable spectrum-group 4 time Monday 12:00:00 band 5000004 40000000

Use the following example to add the upstream frequency 9,500,000 Hz to the list of valid frequencies and change the nominal power level to 5 dBmV. The spectrum manager adjusts frequencies and power levels on this group at 2:00 a.m. local time each day:

Router(config)# cable spectrum-group 3 time 02:00:00 frequency 9500000 5

Use the following example to configure the minimum period before which a frequency hop can occur in seconds:

Router(config)# cable spectrum-group 3 hop period 800

Use the following example to configure the threshold value (expressed as a percentage) of the number of "offline" modems identified before the Cisco uBR7100 series router initiates an automatic frequency hop:

Router(config)# cable spectrum-group 3 hop threshold 40

Use the following example to configure a particular spectrum group as a shared RF spectrum group. Specifying a given spectrum group as "shared" tells the Cisco uBR7100 series router that you want to be sure that upstream frequencies assigned to upstream interfaces are not assigned to additional upstream interfaces:

Router(config)# cable spectrum-group 3 shared

Use the following example to remove a specified spectrum group from your configuration:

Router(config)# no cable spectrum-group 3

Verifying Spectrum Group Characteristics

To verify spectrum group characteristics and to determine if a spectrum group is shared, use the
show cable spectrum-group command:

CMTS01# show cable spectrum-group
22:07:46: %SYS-5-CONFIG_I: Configured from console by console
Group  Frequency      Upstream     Weekly Scheduled            Power   Shared
No.    Band           Port         Availability                Level   Spectrum
       (Mhz)                       From Time:    To Time:      (dBmV)
1       5.000-15.000                                           0       Yes
1      12.000                                                  0       Yes
1      22.000                                                  7       Yes
2      29.000                                                  6       No
2      26.000                                                  0       No
3      35.000-41.000                                           0       No
3      16.000-19.000                                           5       No
5*      5.000-10.000               Thu 21:50:00  Thu 21:45:00  0       Yes 

Tip If you are having difficulty with verification, make sure you entered a valid spectrum group number and type in global cable configuration mode.


Assigning the Spectrum Group and the Upstream Ports

After determining which upstream ports you want assigned to a combiner group, perform the following steps to configure a frequency hop table.

 
Command
Purpose

Step 1 

CMTS01(config)# interface cable slot/port

Enter cable interface configuration mode for the interface to which you wish to assign a spectrum group.

Step 2 

CMTS01(config-if)# cable spectrum-group usport 

Assign the spectrum group to the interface.

Step 3 

CMTS01(config-if)# cable upstream number 
spectrum-group usport 

Assign the upstream ports to the spectrum group for the interface.

Step 4 

CMTS01(config-if)# no cable upstream slot/port 
shutdown

Place the upstream port in the "admin up" state.

Step 5 

CMTS01(config-if)# exit
CMTS01# test cable hop c1/0
CMTS01# test cable hop c1/0

Exit configuration mode and force the system to hop.

Verifying Spectrum Group and Upstream Port Assignments

Use the show cable spectrum-group command to display the current allocation table and frequency assignments.

Activating Cable Address Resolution Protocol Requests

Address Resolution Protocol (ARP) is an Internet protocol used to map IP addresses to MAC addresses on computers and other equipment installed in a network. You need to activate ARP requests on the cable interface so that the Cisco uBR7100 series CMTS can perform IP address resolution on the downstream path.


Note The default values for the commands used in this configuration step are adequate in most cases to configure the Cisco uBR7100 series CMTS.


Activating Cable Address Resolution Protocol (ARP) Requests

To activate ARP requests, use the following command in cable interface configuration mode:

Command
Purpose
CMTS01(config-if)# cable arp

Enable ARP. This is the default.


Verifying ARP Requests

To verify if cable ARP is activated, enter the more system:running-config and look for the cable interface configuration information. If ARP is activated, it does not appear in this output. If ARP is deactivated, it appears in the output as no cable arp.

CMTS01# more system:running-config
Building configuration...
 
Current configuration:
!
interface Cable1/0
ip address 1.1.1.1 255.255.255.0
 no keepalive
 no cable arp 
 cable downstream annex B
 cable downstream modulation 64qam
 cable downstream interleave-depth 32
 cable downstream symbol-rate 5056941
 cable upstream 0 frequency 15008000
 no cable upstream 0 shutdown

Tip If you are having difficulty with verification, make sure you entered the correct port and cable modem card slot number when you activated ARP and when you entered the
show interface cable command.


Activating Host-to-Host Communication (Proxy ARP)

Cable proxy ARP allows the Cisco uBR7100 series CMTS to issue cable ARP requests on behalf of cable modems on the same cable network subnet.


Note Because the downstream and upstreams are separate interfaces, modems cannot directly perform ARP with other modems on the cable plant.



Note The default values for the commands used in this configuration task are adequate in most cases to configure the Cisco uBR7100 series CMTS.


Activating Cable Proxy ARP Requests

To activate cable proxy ARP for host-to-host communications, use the following command in cable interface configuration mode.

Table 3-2 Instructions to Activate Cable Proxy ARP Requests

Command
Purpose
CMTS01(config-if)# cable proxy-arp

Enable proxy ARP on the cable interface. This is the default.


Verifying Cable Proxy ARP Requests

To verify if cable proxy ARP has been activated or deactivated, enter the more system:running-config and look for the cable interface configuration information. If cable proxy ARP has been activated, it does not appear in the output. If cable proxy ARP has been deactivated, it appears in the output as no cable proxy-arp.

CMTS01# more system:running-config
Building configuration...
 
Current configuration:
!
interface Cable1/0

 ip address 1.1.1.1 255.255.255.0
 no keepalive
 no cable proxy-arp
 cable downstream annex B
 cable downstream modulation 64qam
 cable downstream interleave-depth 32
 cable downstream symbol-rate 5056941
 cable upstream 0 frequency 15008000
 no cable upstream 0 shutdown

Tip If you are having difficulty with verification, make sure you entered the correct port and cable modem card slot number when you activated cable proxy ARP.


Configuring DHCP Options

Activating Cable Relay Agent

The cable relay agent is for use with DOCSIS-based DHCP servers that utilize option 82 to automatically map the Ethernet MAC address of a host (subscriber PC) with the cable interface to which it is connected.

With the cable relay agent activated, the Cisco uBR7100 series CMTS inserts the cable interface MAC address into a DHCP packet when the packet is received from a cable interface or another host. The Cisco uBR7100 series CMTS then forwards the packet to the DHCP server.

To activate the cable relay agent, use the following command in cable interface configuration mode.

Command
Purpose
CMTS01(config)# cable relay-agent-option

Activate the cable relay agent. This is the default.



Tip If you are having difficulty with verification, make sure you entered the correct port and cable interface card slot number when you activated the cable relay-agent-option.



Note A DOCSIS-based DHCP server is required. The DHCP server verifies that the defined IP address, if any, returned to the host is valid for the IP subnet on that downstream interface. The IP address must be unique and valid in the subnet for the subscriber to obtain connectivity.


Activating DHCP giaddr

Configure the Cisco uBR7100 series CMTS so it will either assign primary addresses to cable modems and remote hosts, or assign primary addresses to cable modems and secondary addresses to remote hosts.

To configure cable DHCP giaddr functionality, use one of the following commands in cable interface configuration mode.

Command
Purpose

CMTS01(config)# cable dhcp-giaddr primary

or

CMTS01(config-if)# cable dhcp-giaddr policy

Enable cable DHCP giaddr functionality so that primary addresses are assigned to both cable modems and remote hosts.

Enable cable DHCP giaddr functionality so that primary addresses are assigned to cable modems and secondary addresses are assigned to remote hosts.


To disable cable DHCP giaddr functionality (the default) after it has been enabled, enter the no cable dhcp-giaddr command in cable interface configuration mode.

Verifying DHCP giaddr Activation

To determine if DHCP giaddr is activated, enter the show running-config command and look for the cable interface configuration information. If DHCP giaddr is activated, a notation appears in this output. If DHCP giaddr is deactivated, no entry appears in this output.

Configuring Time-of-Day Service

Activating Time-of-Day Service

To activate Time-of-Day (ToD) service for the Cisco uBR7100 series CMTS, use the following command in global configuration mode.

Command
Purpose
CMTS01(config)# cable time-server enable

Enable Time-of-Day (ToD) service for the Cisco uBR7100 series CMTS


To disable ToD service (the default) after it has been enabled, enter the no cable time-server command or the cable time-server disable command in global configuration mode.

Verifying Time-of-Day Service

To determine if ToD service is activated, enter the show running-config command and look for the global cable configuration information. If ToD service is activated, an entry appears in this output. If ToD service is deactivated, no entry appears in this output.

Setting Optional IP Parameters

You can set additional IP parameters to enable downstream echoing of upstream data. To configure these optional IP parameters, perform the following tasks:

"Activating IP Multicast Echo" section

"Activating IP Broadcast Echo" section


Note The default values for the commands used in these configuration steps are adequate in most cases to configure the Cisco uBR7100 series CMTS.


Activating IP Multicast Echo

The Cisco uBR7100 series CMTS echos IP multicast packets by default. To activate IP multicast echo if it has been previously disabled, use the following command in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable ip-multicast-echo

Enable IP multicast echo. This is the default.


To disable IP multicast echo, enter the no cable ip-multicast-echo command in cable interface configuration mode.

Verifying IP Multicast Echo

To determine if IP multicast echo is activated or deactivated, enter the more system:running-config command and look for the cable interface configuration information. If IP multicast echo is activated, there is no notation in the output, because this is the default setting. If IP multicast echo is deactivated, a notation appears in the output:

CMTS01# more system:running-config
Building configuration...
 
Current configuration:
!
interface Cable1/0

 ip address 1.1.1.1 255.255.255.0
 no keepalive
 no cable ip-multicast-echo 
 cable downstream annex B
 cable downstream modulation 64qam
 cable downstream interleave-depth 32
 cable upstream 0 frequency 15008000
 no cable upstream 0 shutdown

Tip If you are having difficulty with verification, make sure that you have entered the correct slot and port numbers when you entered cable interface configuration mode.


Activating IP Broadcast Echo

By default, the Cisco uBR7100 series CMTS does not echo IP broadcast packets. To activate IP broadcast echo, use the following command in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable ip-broadcast-echo

Enable IP broadcast echo.


To disable IP broadcast echo when it is enabled, enter the no cable ip-broadcast-echo command in cable interface configuration mode.

Verifying IP Broadcast Echo

To determine if IP broadcast echo is activated or deactivated, enter the more system:running-config command, and look for a notation in the cable interface configuration information:

CMTS01# more system:running-config
Building configuration...
 
Current configuration:
!
interface Cable1/0

 ip address 1.1.1.1 255.255.255.0
 no keepalive
 cable ip-broadcast-echo 
 cable downstream annex B
 cable downstream modulation 64qam
 cable downstream interleave-depth 32
 cable upstream 0 frequency 15008000
 no cable upstream 0 shutdown

Activating Packet Intercept Capabilities

To activate packet intercept functionality, use the following commands in cable interface configuration mode.

Command
Purpose
CMTS01(config-if)# cable intercept 
xxxx.xxxx.xxxx

Specify a MAC address on the cable network for which interception capabilities are to be activated. A limit of 10 MACs exist.

CMTS01(config-if)# no cable intercept 
xxxx.xxxx.xxxx

Disable interception after it is enabled.


Configuring Cable Modulation Profiles

To configure cable profiles (deviating from defaults), perform the following as necessary:

"Configuring Cable Modulation Profiles" section

"Configuring QoS Profiles" section

"Setting QoS Permission" section

"Enforcing a QoS Profile Assignment" section (Optional)

"Monitoring and Maintaining QoS for Higher Priority Traffic" section.

Configuring Cable Modulation Profiles

In this step, you are defining the elements used in a cable modulation profile. The Cisco uBR7100 series CMTS supports as many as 8 cable modulation profiles. Profile 1 is the default.


Caution If you modify a cable modulation profile from default parameters, you are changing the physical layer. Changing physical layer characteristics affects router performance and function; therefore, only an expert should perform this task.

The following modulation profile values are configurable:

Interval usage code (iuc)—Valid values are initial, long, reqdata, request, short, and station.

Fec-tbytes—The number of bytes that can be corrected per FEC codeword. Valid range is 0 to 10 bytes, where 0 means no FEC. This is the number of bytes that the FEC decoder can correct within a codeword. A codeword consists of information bytes, called k-bytes and parity bytes for error correction. The number of parity bytes is equal to two times the number of correctable error (T). The size of T is dictated by channel impairments.

Fec-len—FEC codeword length. Valid range is 16 to 254 bits. This value enables an efficiency mode wherein all codewords are fixed in size. In a fixed operation, all codewords are the same size with the last codeword padded with nulls if there are not enough information bytes to fill it entirely. The efficiency is gained by not having to transmit the nulls that pad the last codeword.

Burst-len—Maximum burst length in bytes. 0 means no limit on burst length. This is used to determine the breakpoint between packets that use the short data grant burst profile and packets that use the long data grant burst profile. If the required upstream time to transmit a packet is greater than this value, the long data grant burst profile is used. If the time is less than or equal to this value, the short data grant burst profile is used.

Guard-t—Guard time in symbols. This is the time between successive bursts. It is the blank time at the end of a burst transmission that exists to ensure that one burst ends before another burst starts.

Mod—Modulation. Valid values are "16qam" and "qpsk". Modulation type is used to select between four bits per modulation symbol (QAM-16) or two bits per modulation symbol (QPSK). QAM-16 uses both phase and amplitude to carry information. QPSK carries information in the phase of the signal carrier. QAM-16 requires approximately 7 dB higher C/N to achieve the same BER as QPSK, but it transfers information at two times the rate of QPSK.

Scrambler—Enable or disable scrambler. Valid values are scrambler and no-scrambler. Scrambler is used to create an almost random sequence of transmission symbols, which ensures an even spectral distribution of energy transmitted within the channel. The scrambler seed is an initial value that is used to start the pseudo-randomizer to scramble the bits. Because both the transmitter and receiver know the seed value, the scrambling can be reversed at the receiver, leaving only the original data.

Seed—Scrambler seed in hexadecimal format. Valid range is 0x0000 to 0x7FFF.

Diff—Enable or disable differential encoding. Valid values are diff and no-diff. Differential encoding is a technique wherein the information is transmitted by the phase change between two modulation symbols instead of by the absolute phase of a symbol. This technique makes the absolute phase of the received signal insignificant and has the effect of doubling the BER for the same C/N.

Pre-len—Preamble length in bits. Valid range is 2 to 128 bits. Preamble length (and Preamble offset) are used to define a synchronizing string of modulation symbols used to let the receiver find the phase and timing of the transmitted burst.

Last-cw—Handling of FEC for last codeword. Valid values are fixed for fixed codeword length, and shortened for shortened last code word.

Uw-len—Upstream unique word length. Enter uw8 for 8-bit unique words, or uw16 for 16-bit unique code words.

To create or change a cable modulation profile, use the following command in global configuration mode.

Command
Purpose

CMTS01(config)# cable modulation-profile profile iuc fec-tbytes fec-len burst-len guard-t mod scrambler seed diff pre-len last-cw uw-len

Create a new cable modulation profile with a profile number or modify an existing profile.


In the following example, the request burst for cable modulation profile 2 is defined to have 0 fec-tbytes, 16 kbytes fec-len, a burst-len of 1, a guard time of 8, a mod value of qpsk, scrambler enabled with a seed value of 152, differential encoding disabled, a preamble length of 64 bits, a fixed code word length, and 8-bit unique words for upstream unique word length.

CMTS01(config)# cable modulation-profile 2 request 0 16 1 8 qpsk scrambler 152 no-diff 64 
fixed uw8

To remove a cable modulation profile, use the no cable modulation-profile profile command in global configuration mode. You can use this command to remove all modulation profiles except for modulation profile 1.


Tip Entering no cable modulation-profile 1 sets all parameters in profile 1 to the default values.


Verifying Cable Modulation Profiles

To determine if a cable modulation profile is created, enter the show cable modulation-profile command.

A sample output is shown in the following example:

CMTS01# show cable modulation-profile
Mo IUC     Type  Preamb Diff FEC err FEC   Scrambl Max  Guard Last Scrambl Preamb 
                 length enco correct T     seed    B    time  CW           offset 
                                         bytes          size size   short
1  request qpsk  64     no   0x0     0x10  0x152   1    8     no   yes     56 
1  initial qpsk  128    no   0x5     0x22  0x152   0    48    no   yes     0 
1  station qpsk  128    no   0x5     0x22  0x152   0    48    no   yes     0 
1  short   qpsk  72     no   0x5     0x4B  0x152   0    8     no   yes     48 


Note If you have CBR scheduling parameters and IP precedence rate limits defined in the QoS profile, the command output reveals this. Refer to the "Monitoring and Maintaining QoS for Higher Priority Traffic" section. The show cable modulation-profile and show interface cable commands are enhanced to reflect the state of the new MAC scheduler for the specified upstream port.



Tip If you are having difficulty with verification, ensure that the system is in global configuration mode, and that you typed the correct modulation profile number and elements when you entered the command.


The preamble offset is calculated from the modulation profile entries. The preamble offset is the distance the CMTS looks into the preamble to determine where the preamble starts. The CMTS does not need to look at the entire preamble in all instances. A shorter preamble has less overhead and time associated with that type of burst request. In general, you should use an offset of "0" for initial/station maintenance because you need to separate these packets as distinctly as possible.

The offset for QPSK is shorter because of the way DOCSIS specifies the preamble. For QPSK, it only takes a preamble length of 256 bits to separate frames, whereas with QAM-16, the date rate is much higher. Utilization of a larger preamble is necessary.

Configuring QoS Profiles

The Cisco uBR7100 series CMTS supports multiple QoS profiles. QoS profile 1 is used during cable interface registration and QoS profile 2 is the default QoS profile. Both of these profiles are preconfigured and cannot be removed. However, you can modify these profiles and create additional Q0S profiles for various traffic flows.

To create or change a QoS profile, use the first command below, plus as many of the additional commands as are necessary to make the changes you require. All of the QoS profile commands are global configuration commands.

Command
Purpose
CMTS01(config)# cable qos-profile 
groupnum

Create a new QoS profile with a profile number of groupnum, or modify an existing profile.

CMTS01(config)# cable qos-profile 
groupnum ip-precedence bits

Set the bits in the Type of Service (ToS) byte that enable you to configure individual data rate limits on a per-modem basis. Valid values are from 0 to 7.

CMTS01(config)# cable qos-profile 
groupnum guaranteed-upstream rate

Set the guaranteed minimum upstream rate in kbps. Valid values are from 0 to 100000 kbps. Default = 0 (no reserved rate).

CMTS01(config)# cable qos-profile 
groupnum max-burst size

Set the maximum upstream transmit burst size in minislots that the cable modem can send for any single transmit burst. Valid values are from 0 to 255 minislots. Default = 0 (no limit).

CMTS01(config)# cable qos-profile 
groupnum max-upstream rate

Set the maximum upstream data rate in kbps that a cable modem using this QoS profile will send. Valid values are from 0 to 100000 kbps. Default = 0 (no upstream rate limit.)

CMTS01(config)# cable qos-profile 
groupnum max-downstream rate

Set the maximum downstream data rate in kbps that a cable modem using this QoS profile will receive. Valid values are from 0 to 100000 kbps. Default = 0 (no downstream rate limit.)

CMTS01(config)# cable qos-profile 
groupnum priority number 

Assign a relative priority number for the upstream traffic associated with this QoS profile. Valid values are from 0 to 7, with 7 being the highest priority. Default = 0.

CMTS01(config)# cable qos-profile 
groupnum tos-overwrite value

Overwrite the ToS byte in the IP datagrams received on the upstream before forwarding them downstream. Set the mask bits to a hexadecimal value to help the CMTS identify datagrams for QoS on the backbone.



Note You can use a single cable qos-profile command to configure multiple parameters for the selected QoS profile number.



Tip Use the no cable qos-profile groupnum command to remove an optional QoS profile, or in the case of QoS profiles 1 and 2, to return the parameters to their default values.


Verifying QoS Profiles

To determine if a QoS profile has been created, and to see how it is configured, enter the
show cable qos profile command:

CMTS01# show cable qos profile
Service Prio Max       Guarantee Max        Max tx TOS  TOS   Create     B		 	 	 	 	 	 	IP
class        upstream  upstream  downstream burst  mask value by         priv	 	 	 	 prec
             bandwidth bandwidth bandwidth                               enab	 	 	 	enab
1       0    0         0         0          0      0x0  0x0   cmts       no	 	 	 	 	 	no
2       0    64000     0         1000000    0      0x0  0x0   cmts       no	 	 	 	 	 	no
3       0    3120 	 	 	 	 	 	31200 	 	 	 	 	0       	 	 	 	0      0x0  0x0   cmts       yes	 	 	
 	 		no
4       7    87200 	 	 	 	 87200 	 	 	 	 	0    	 	 	 	 	 	 0      0x0  0x0   cmts 	 	 	 	 	 	 yes	 	
 	 	 	yes
5	 	 	 	 	 	 	 	0 		 	 	 256000 	 	 	 	128000    1000000    0      
0x0  0x0   cm         no	 	 	 	 	 yes


Tip If you are having difficulty with verification, make sure you typed the correct QoS profile number and profile elements when you entered the command in global configuration mode.



Note Cable modems that register continuously and fail consume more resources than cable interfaces that stay registered. Assign customers who do not pay for service to QoS profile 3.



Caution DOCSIS 1.0-certified cable interfaces that are given a short max-burst size might be unable to transmit large packets to the headend.

Setting QoS Permission

The Cisco uBR7100 series CMTS supports the creation of QoS table entries by SNMP or by CM registration requests. You can also configure a Cisco uBR7100 series CMTS to dynamically update QoS table entries via SNMP.

To set QoS table access, use one or more of the following commands in global configuration mode.

Command
Purpose

CMTS01(config)# cable qos permission create-snmp

Enable SNMP access to create entries in the QoS tables.

CMTS01(config)# cable qos permission update-snmp

Enable SNMP access to dynamically update entries in the QoS tables.

CMTS01(config)# cable qos permission modems

Enable QoS table entries to be created using a CM registration requests.

CMTS01(config)# no cable qos permission

Disable both SNMP access and CM registration access to the QoS tables.


Verifying QoS Permission

To verify QoS permissions, enter the show cable qos permission command:

CMTS01# show cable qos permission
Create by SNMP  Update by SNMP  Create by modems
no              no              yes

Tip If you are having difficulty with verification, make sure you typed the correct QoS profile number and profile elements in global configuration mode.



Note QoS profiles can be changed dynamically, permitting service tiers that are time-sensitive. This provides more bandwidth during business hours than on weekends for telecommuter applications.


Enforcing a QoS Profile Assignment

To override the provisioned QoS profile of a CM and enforce a CMTS-specified QoS profile, use the following command in global configuration mode.

Command
Purpose
CMTS01(config)# cable qos permission enforce 
index

Assigns the QoS profile, specified by the index number, to all CMs attempting to connect to theCisco uBR7100 series CMTS.


Verifying a QoS Profile Assignment


Step 1 Load the Cisco uBR7100 series CMTS and wait for the CMs to come online as indicated by the show cable modem command.

Notice that the CMs are getting their provisioned class of service as indicated by the
show cable modem and show cable qos profile commands.

Step 2 Configure any QoS profile at the CMTS with a specific index number (for example index 1) by using the SNMP/CLI.

Step 3 Enter the global command cable qos permission enforce 1.

Step 4 Enter the clear cable modem all reset global configuration command to force the CMs to reregister with the CMTS.

Notice that the CMs are assigned temporarily the CMTS-defined PRE_REGISTRATION QoS profile with index 2 until the CMs register with the CMTS.

Step 5 Use the debug cable reg command to see that the provisioned QoS parameters of the CMs are overwritten at the CMTS during registration. Notice that at the end of the registration, the CM gets the user-enforced QoS profile as indicated by the show cable modem and show cable qos profile commands.


Setting Quality of Service (QoS) for Higher Priority Traffic

This feature describes the software enhancements and procedures that support QoS for higher priority traffic. These enhancements include improved support for:

Delay/jitter requirements of higher priority traffic

Increase in per-modem data throughput

New MAC scheduler

MAC messaging enhancements to better support real time responses to high priority service requests

Refer to the following procedures for setting QoS for higher priority traffic:

"Configuring a QoS Profile for Higher Priority Traffic" section

"Monitoring and Maintaining QoS for Higher Priority Traffic" section

Configuring a QoS Profile for Higher Priority Traffic

Perform these steps to configure a QoS modulation profile:

 
Command
Purpose

Step 1 

Router(config)# cable qos-profile n name

Assigns a name to the QoS profile.

Step 2 

Router(config)# cable qos-profile n priority

Sets the upstream traffic priority.

Step 3 

Router(config)# qos-profile n max-upstream

Sets the maximum upstream traffic rate.

Step 4 

Router(config)# qos-profile n guaranteed-upstream

Sets the guaranteed upstream traffic rate.

Step 5 

Router(config)# qos-profile n grant-size

Sets the size for unsolicited grants.

Step 6 

Router(config)# qos-profile n grant-interval

Sets the interval for unsolicited grants.

Step 7 

Router(config)# qos-profile n max-burst

Sets the maximum rate for upstream transmission bursts.

Step 8 

Router(config)# qos-profile n ToS-overwrite

Sets the mask bits to overwrite the Type of Service byte.

Step 9 

Router(config)# qos-profile n max-downstream

Sets the maximum downstream traffic rate.

Step 10 

Router(config)# qos-profile n privacy

Enables baseline privacy.

Step 11 

Router(config)# qos-profile n ip-precedence

Downstream settings are based on IP precedence.

Monitoring and Maintaining QoS for Higher Priority Traffic

Use the following commands to monitor and maintain QoS for higher priority traffic.

Command
Purpose
Router# show cable qos profile n 

Displays the configuration for the specified profile.

Router# show interface cable x/y sid

Displays each QoS profile configured for the specified cable interface.

Router# show interface cable x/y upstream 

Displays QoS statistics for the upstream channel.


The following example shows how the cable router (mgmt) creates a CM with a QoS profile 30:

Router(config)# cable qos profile 30 name qostest
Router(config)# cable qos profile 30 grant-int 55
Router(config)# cable qos profile 30 grant-size 100
Router(config)# cable qos profile 30 guaranteed 60000
Router(config)# cable qos profile 30 ip-prec 7
Router(config)# cable qos profile 30 max-bur 256
Router(config)# cable qos profile 30 max-down 3000
Router(config)# cable qos profile 30 max-up 6000
Router(config)# cable qos profile 30 prior 7
Router(config)# cable qos profile 30 privacy
 
router# show cable qos profile 30
ID Prio Max       Guarantee Max         Max   ToS  ToS   Create  B     IP prec.
        upstream  upstream  downstream  tx    mask value by      priv  rate
        bandwidth bandwidth bandwidth   burst                    enab  enab
30 7    6000000   60000000  100000000   256   0x0  0x0    mgmt    yes   no

To configure a QoS profile, enter the cable qos profile global configuration command. To set default values for profile group numbers 1 or 2, or to remove the QoS profile if no specific parameters remain, enter the no form of this command.

cable qos profile {groupnum | grant-interval {interval}| grant-size {size} | guaranteed-upstream {rate} | ip-precedence {value} | max-burst {rate} | max-downstream {rate} | max-upstream {rate} | name {string} | priority {value} | privacy | ToS-overwrite {value}}

no cable qos profile {groupnum | grant-interval {interval} | grant-size {size} | guaranteed-upstream {rate} | ip-precedence {value} | max-burst {rate} | max-downstream {rate} | max-upstream {rate} | name {string} | priority {value} | privacy | ToS-overwrite {value}}

The following table describes the syntax and values for these commands.

Syntax
Valid Values

groupnum

QoS profile group number. Qos profiles 1 and 2 are required by the system. QoS profile 1 is used during registration, and QoS profile 2 is the default QoS profile. Both profiles are preconfigured and cannot be removed. However, you can modify these profiles.

grant-interval

The periodic interval in microseconds at which the CM wants to send the fixed-sized upstream MAC frames. This value is used to compute the period between constant bit rate (CBR) slots for the CM. Valid range is 0 to 65535.

grant-size

The size of the DOCSIS MAC frame the CM wants periodically to send on the upstream transmission. This value in bytes does not include any PHY layer overhead. It includes the complete fixed MAC frame size starting from the frame control byte to the CRC of the protocol data unit (PDU). This parameter is used by the CMTS to set the size of the periodic CBR slot for the CM after adding the PHY overhead.

guaranteed-upstream

Guaranteed minimum upstream rate in kilobytes per second. Valid values are 0 through 100000. Default value is 0 (no reserved rate).

ip-precedence

Bits in the ToS byte that enable you to configure individual data rate limits on a per modem basis. Valid values are 0 to 7.

max-burst

Maximum upstream transmit burst size in bytes that the modem can send for any single transmit burst. Valid values are 0 to 65535 bytes. Default value is 0 (no limit).

max-downstream

Maximum downstream data rate in kilobytes per second that a modem using this QoS profile receives. Valid values are 0 to 100000. Default value is 0 (no downstream rate limit).

max-upstream

Maximum upstream data rate in kilobytes per second that a modem using this QoS profile receives. Valid values are 0 to 255. Default value is 0 (no upstream rate limit).

name

QoS name string.

priority

Relative priority number assigned to upstream traffic by this QoS profile. Valid values are 0 to 7, with 7 being the highest priority. Default value is 0.

privacy

Enables cable baseline privacy.

ToS-overwrite

Overwrite the ToS field in the IP datagrams received on the upstream before forwarding them downstream (or IP backbone). This parameter sets the hexadecimal mask bits to a hexadecimal value, thereby helping the CMTS identify datagrams for QoS on the backbone. Valid range is 0x0 to 0xFF.

value

The value substituted for the ToS value. See ToS-overwrite.


Refer to the following example to configure QoS profile 4 with guaranteed upstream of 2 kbps, maximum transmission burst of 2, an IP precedence of 7, a maximum downstream rate of 300 kbps, with a priority of 4, cable baseline privacy set, and a ToS-overwrite mask and value byte (in hex) of 0x7:

Router(config)# cable qos profile 4 name Mondayqos
Router(config)# cable qos profile 4 guaranteed-upstream 2
Router(config)# cable qos profile 4 max-burst 2
Router(config)# cable qos profile 4 ip-precedence 7 max-downstream 300
Router(config)# cable qos profile 4 priority 4
Router(config)# cable qos profile 4 ToS-overwrite 0x7

To display QoS profiles, use the show cable qos profile privileged EXEC configuration command.


Note An optional "verbose" parameter is added:
show cable qos profile qos profile index verbose
The qos profile index option displays the index of the specified QoS profile. The verbose option displays all details for the specified QoS profile index.


The following example shows the full QoS table for profile 30:

router# show cable qos profile 30 verbose
Profile Index                           30
Name                                    test
Upstream Traffic Priority               7
Upstream Maximum Rate (bps)             6000000
Upstream Guaranteed Rate (bps)          60000000
Unsolicited Grant Size (bytes)          100
Unsolicited Grant Interval (usecs)      55000
Upstream Maximum Transmit Burst (bytes) 256
IP Type of Service Overwrite Mask       0x0
IP Type of Service Overwrite Value      0x0
Downstream Maximum Rate (bps)           100000000
Created By                              mgmt
Baseline Privacy Enabled                yes
IP precedence rate limits
 IP precedence						                            2
 Rate Limit                             100000

Table 3-2 describes the fields shown in the show cable qos profile displays.

Field
Description

Profile Index

Profile number.

Name

The name string for this profile.

Upstream Traffic Priority

Priority level for upstream traffic.

Upstream Maximum Rate (bps)

Maximum upstream transmission rate in bits per second.

Upstream Guarantee Rate (bps)

Guaranteed minimum upstream rate in bits per second.

Unsolicited Grant Size (bytes)

Number of grant-size parameters in bytes. Grant size is used by the CMTS to set the size of the periodic CBR slot for the CM after adding the PHY overhead.

Unsolicited Grant Interval (usecs)

Number of unsolicited grant intervals in microseconds. The grant-interval parameter is used to compute the period between CBR slots for the CM.

Upstream Maximum Transmit Burst (bytes)

Maximum transmit burst size in bytes.

IP Type of Service Overwrite Mask

Hex value of the mask bits.

IP Type of Service Overwrite Value

Value of the mask byte. This is the value the CMTS will overwrite into the ToS field (after masking bits specified in the ToS-mask parameter) of the IP datagram before forwarding the datagram into IP backbone/downstream. The IP ToS overwrite feature helps to propagate cable access QoS onto the IP backbone.

Downstream Maximum Rate (bps)

Minimum upstream transmission rate in bits per second.

Created by

Identity of the profile creator.

Baseline Privacy Enabled

Reports yes if Baseline Privacy is enabled for this QoS profile. Reports no if Baseline Privacy is not enabled for this Qos profile.

IP Precedence rate limits

Value of the IP precedence and the transmission rate limit in bits per second.


Table 3-3 Related Commands

Command
Description

cable qos permission

Sets permissions for updating QoS tables.

cable qos profile

Configures QoS profiles.

show cable qos permission

Displays the status of permissions for updating QoS tables.


In the sample show cable qos profile output response, note the added IP precedence column:

CMTS01# show cable qos profile
Service Prio Max       Guarantee Max        Max tx TOS  TOS   Create     B		 	 	 	 	 	 	IP
class        upstream  upstream  downstream burst  mask value by         priv	 	 	 	 prec
             bandwidth bandwidth bandwidth                               enab	 	 	 	enab
1       0    0         0         0          0      0x0  0x0   cmts       no	 	 	 	 	 	no
2       0    64000     0         1000000    0      0x0  0x0   cmts       no	 	 	 	 	 	no
3       0    3120 	 	 	 	 	 	31200 	 	 	 	 	0       	 	 	 	0      0x0  0x0   cmts       yes	 	 	
 	 		no
4       7    87200 	 	 	 	 87200 	 	 	 	 	0    	 	 	 	 	 	 0      0x0  0x0   cmts 	 	 	 	 	 	 yes	 	
 	 	 	yes
5	 	 	 	 	 	 	 	0 		 	 	 256000 	 	 	 	128000    1000000    0      
0x0  0x0   cm 	 	 	 	 	 	 	 	 no	 	 	 	 	 yes

The software provides QoS based on the CM SID. Every QoS profile carries a parameter maximum downstream rate which is used to provide peak rate limiting and traffic shaping on the downstream. When the particular CM supports combined high priority and data traffic, rate exceeded data packets might shut out or delay higher priority packets, degrading quality. As a solution, IP precedence bits are used as a basic differentiator to provide independent rate limits for different traffic streams as desired.

The show interface cable x/y upstream port # command is also enhanced to reflect the current state of the new MAC scheduler for the specified upstream port as shown in the following example:

cmts# show interface cable 1/0 upstream 0
Cable1/0: Upstream 0 is up
     Received 68 broadcasts, 0 multicasts, 20811 unicasts
     0 discards, 99 errors, 0 unknown protocol
     20879 packets input, 0 corrected, 0 uncorrectable
     99 noise, 0 microreflections
     Total Modems On This Upstream Channel : 2 (2 active)
     Default MAC scheduler
     Queue[Cont Mslots]  1/104, fifo queuing, 0 drops
     Queue[Rng Polls]  0/20, fifo queuing, 0 drops
     Queue[CIR Grants]  0/20, fair queuing, 0 drops
     Queue[BE Grants]  0/30, fair queuing, 0 drops
     Queue[Grant Shpr]   0/30, calendar queuing, 0 drops
     Reserved slot table currently has 5 CBR entries
     Req IEs 176103, Req/Data IEs 0
     Init Mtn IEs 540, Stn Mtn IEs 101
     Long Grant IEs 10042, Short Grant IEs 405
     Total channel bw reserved 200000 bps
     CIR admission control not enforced
     Current minislot count   : 2099853    Flag: 1
     Scheduled minislot count : 2100020    Flag: 1

The show interface sid command is also enhanced to display the type of SID—whether it is "Static" versus "Dynamic".

cmts# show interface cable x/y sid

Sid

Prim Sid

Type

Online State

Admin Status

QoS

Create Time

IP Address

MAC Address

2

 

stat

online

enable

4

12:10:25

1.11.51.37

0010.7b6b.722d

4

2

dyn

online

enable

5

12:10:30

1.11.51.37

0010.7b6b.722d

You can optimize the physical layer parameters on an upstream channel. An example is provided for physical layer parameters that can be used on the CMTS for upstream channels expected to support high priority traffic density. These parameters minimize the physical layer overhead encountered for each fixed sized (89 bytes) packet. The resulting fine tuning gives a direct improvement in the number of CBR high priority connections that can be admitted on a single upstream channel.

Configure the following settings for the upstream channel to maximize the number of CBR
connections:

Minislot size: 8

Symbol rate: 1280 Ksymbols/sec

Modulation type: QPSK

Preamble length: 72 bits

FEC (T bytes): 2 bytes

FEC codeword length: 52 bytes

Guard time: 8 symbols

Last codeword: shortened last codeword

To configure the above modulation profile at the CMTS, use the following commands:

Create a new qpsk modulation profile template m with all default parameters, except the "short grant" profile which has special parameters as given below:

cmts(config)# cable modulation-profile m qpsk
cmts(config)# cable modulation-profile m short 2 52 16 8 qpsk scrambler 152 diff 72 
shortened uw8

Configure upstream port n on a given interface to use minislot size of 8 ticks and above modulation profile template m:

cmts(config-if)# cable upstream n minislot-size 8
cmts(config-if)# cable upstream n modulation-profile m

Setting and Viewing Concatenation

To turn concatenation off or on from the CMTS, use the cable upstream concatenation interface configuration command. To turn off concatenation from the default state of on, use the no form of this command.

cable upstream n concatenation

no cable upstream n concatenation


Note Concatenation is part of DOCSIS 1.0 extension support. Concatenation must be supported at both the CMTS and the CM. When enabled on both the CMTS and the CM, the CMTS can receive a concatenated burst of multiple MAC frames from the CM.


Setting Concatenation

 
Command
Purpose

Step 1 

Router(config-if)# no cable upstream n concatenation

Turns off concatenation on the specified channel.

Step 2 

Router(config-if)# cable upstream n concatenation

Turns on concatenation on the specified channel.


Tip Concatenation is enabled by default.



Caution Turning off concatenation instructs the CM that the CMTS does not want the CM to concatenate. It is actually up to the CM not to concatenate. If the CM concatenates even after the no cable upstream number concatenation interface command is issued, the CM might concatenate incorrectly. Such a CM is considered noncompliant.

Viewing Concatenation Status

Use the following command to monitor concatenation:

Command
Purpose
Router# show controller cable slot/port

Displays the current status of concatenation for the specified slot and port.


The following display indicates that concatenation is turned off.

Lab-CMTS# show controller cab 1/0
Interface Cable1/0
Hardware is BCM3210 FPGA
 idb 0x6182BE18 MAC regs 0x3D900000 PLX regs 0x3D800000
 rx ring entries 1024 tx ring entries 128 MAP tx ring entries 128
 Rx ring 0x4B09A400 shadow 0x61849408 head 359
 Tx ring 0x4B09C440 shadow 0x6184A478 head 85 tail 85 count 0
 MAP Tx ring 0x4B09C880 shadow 0x6184A8E8 head 7 tail 7 count 0
 
 MAP timer sourced from slot 4
 
 throttled 0 enabled 0 disabled 0
 Rx: spurious 341 framing_err 0 hcs_err 2 no_buffer 0 short_pkt 2
     no_enqueue 0 no_enp 1 miss_count 0 latency 16
     invalid_sid 0 invalid_mac 0 bad_ext_hdr_pdu 0 concat 0 bad-concat 0
 Tx:  full 0 drop 0 stuck 0 latency 1
 MTx: full 0 drop 0 stuck 0 latency 9
 Slots 68056 NoUWCollNoEngy 15 FECorHCS 2 HCS 0
 Req 1803579865 ReqColl 1 ReqNoise 276120 ReqNoEnergy 0
 ReqData 0 ReqDataColl 0 ReqDataNoise 0 ReqDataNoEnergy 0
 Rng 143099 RngColl 0 RngNoise 3891
 FECBlks 0 UnCorFECBlks 0 CorFECBlks 0
 MAP FIFO overflow 0, Rx FIFO overflow 0, No rx buf 0
 DS FIFO overflow 0, US FIFO overflow 0, US stuck 0
 Bandwidth Requests= 0xFFC9
 Piggyback Requests= 0xA1D
 Ranging Requests= 0x22039
 Timing Offset = 0x0
Bad bandwidth Requests= 0x31BC
 No MAP buffer= 0x0
 Cable1/0 Downstream is up
Frequency not set, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
  FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
  Downstream channel ID: 0
 Cable1/0 Upstream 0 is up
Frequency 20.208 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
  Spectrum Group is overridden
  SNR - Unknown
  Nominal Input Power Level 0 dBmV, Tx Timing Offset 4667
  Ranging Backoff automatic (Start 0, End 3)
  Ranging Insertion Interval automatic (60 ms)
  Tx Backoff Start 0, Tx Backoff End 4
  Modulation Profile Group 1
concatenation is disabled