Table Of Contents
Configuring the Cisco uBR-MC28C Cable Modem Card
Related Features and Technologies
Supported Standards, MIBs, and RFCs
Configuring the Cisco uBR-MC28C Cable Modem Card
Verifying Downstream Center Frequency
cable downstream interleave-depth
cable upstream differential-encoding
cable upstream freq-adj averaging
cable upstream modulation-profile
Configuring the Cisco uBR-MC28C Cable Modem Card
This feature module describes configuring the Cisco uBR-MC28C cable modem card. The card contains two downstream and eight upstream ports configured in two independent Cable Modem Termination System (CMTS) media access control (MAC) domains. A MAC domain is a collection of upstream and downstream channels for which a single MAC allocation and management protocol operates. Each domain on the Cisco uBR-MC28C cable modem card includes one downstream and four upstream ports. Both domains operate independently of each other.
This feature module includes the following sections:
•Supported Standards, MIBs, and RFCs
Feature Overview
The Cisco uBR-MC28C cable modem card resides in a Cisco uBR7200 series universal broadband router and supports downstream and upstream traffic to and from Data-Over-Cable Service Interface Specification (DOCSIS)-based cable modems (CMs). The card supports 6-MHz National Television Systems Committee (NTSC) channel operation, using standard (STD), Harmonic Related Carrier (HRC), or Incremental Related Carrier (IRC) frequency plans conforming to EIA-S542. The card supports downstream channels in the 54-to-860 MHz range, therefore, with upstream ranges of 5 to 42 MHz.
Note While you can use the Cisco uBR-MC28C cable modem card in 8-MHz international cable plants, the card ignores 2 MHz of available channel width, operates at a maximum downstream bandwidth of 27 Mbps, and limits upstream choices to the range below 42 MHz.
The Cisco uBR-MC28C cable modem card contains two downstream modulators and eight upstream demodulators with the following modulation defaults beginning in Cisco IOS Release 12.1(2)EC1:
•64 Quadrature Amplitude Modulation (QAM) downstream
•Quadrature Amplitude Phase-Shift Keying (QPSK) upstream
These values are based on the Cisco default modulation profile #1 that ships with product. Modulation profile #1 values are illustrated below:
cmts1# show cable modulation-profile
Mod IUC Type Preamb Diff FEC FEC Scrambl Max Guard Last Scrambl Preamblength enco T CW seed B time CW offsetBYTES size size size short1 request qpsk 64 no 0x0 0x10 0x152 1 8 no yes 9521 initial qpsk 128 no 0x5 0x22 0x152 0 48 no yes 8961 station qpsk 128 no 0x5 0x22 0x152 0 48 no yes 8961 short qpsk 72 no 0x5 0x4B 0x152 6 8 yes yes 9441 long qpsk 80 no 0x8 0xDC 0x152 0 8 yes yes 936interface Cable4/0ip address 10.20.115.33 255.255.255.224ip helper-address 10.0.0.2load-interval 30no keepalivecable spectrum-group 1cable insertion-interval 100cable downstream annex Bcable downstream modulation 64qamcable downstream interleave-depth 32cable downstream frequency 576000000cable upstream 0 spectrum-group 2no cable upstream 0 shutdownno cable upstream 1 shutdownno cable upstream 2 shutdownno cable upstream 3 shutdownendThe Cisco uBR-MC28C cable modem card supports all DOCSIS 1.0-specified Annex B radio frequency (RF) data rates, channel widths, and modulation schemes. Table 1 shows the supported DOCSIS data rates. The card outputs +42 dBmV and +/- 2 dBmV.
Table 1 DOCSIS Data Rates
Caution While the Cisco uBR-MC28C contains a total of two downstream and eight upstream ports, upstream ports are fixed to a specific downstream. You cannot mix and match upstream ports to downstreams ports. Instead, the card is configured to support a dual one-downstream-to-four-upstream port arrangement.
Tips For those familiar with current Cisco cable modem cards, you can think of the Cisco uBR-MC28C card as two Cisco uBR-MC14C cable modem cards in one. The Cisco uBR-MC28C card supports a pair of downstream QAM 64 or QAM 256 ports, and four QPSK or QAM 16 upstream ports. Each port set is independent of the other. Upstream and downstream ports are not shared across the two MAC domains.
The Cisco uBR-MC28C cable modem card contains a color-coded label that identifies and groups the two supported downstream-to-upstream port sets. Figure 1 shows the dual downstream and upstream port pairs.
Figure 1 Cisco
uBR-MC28C Face Plate View
The two downstream ports are labelled DS0 and DS1. Their corresponding upstream ports are labelled U0 through U3, applicable to each port set. To configure the Cisco uBR-MC28C cable modem card, use the interface type slot/port commands:
•Type—Cable
•Slot—Slot number refers to the downstream port; value is 0 or 1.
•Port—Port number refers to the upstream port associated with the specific downstream port; value is from 0 to 3.
Table 2 maps the Cisco uBR-MC28C cable modem card's physical port domains and interfaces.
Table 2
Interface to Port Mapping
Note The Cisco uBR-MC28C cable modem card operates using Cisco IOS Release 12.1(3a)EC1 or later release.
The card can be housed in a Cisco uBR7223, Cisco uBR7246, or the Cisco uBR7246 VXR universal broadband router. The card supports synchronization with a Cisco clock card in a Cisco uBR7246 VXR. The card distributes the clock signal to CMs supporting the clock feature set that are attached to specific network segments.
Benefits
The Cisco uBR-MC28C cable modem card:
•Expands the capacity of a Cisco uBR7200 series universal broadband router, providing the highest port density in Cisco cable modem cards available today; the card offers another downstream channel and additional upstream channels
•Gives cable operators additional flexibility in partitioning the cable plant to address growing subscriber bandwidth demands; enables cost-effective scaleability of services and subscribers
•Offers advanced functionality, supporting DOCSIS 1.0 and DOCSIS 1.0 extensions, as well as other Cisco IOS Release 12.1(3a)EC1 features such as Hot Standby 1+1 Redundancy and Dynamic Upstream Modulation
•Supports all earlier Cisco cable modem card features including:
–Online insertion and removal (OIR), allowing key system components to be added or removed without powering off the chassis
–Downloadable software, allowing new Cisco IOS images to be remotely loaded
•Interoperates with DOCSIS-compliant cable modems and other RF customer premises equipment (CPE) devices, including the Cisco uBR910 series cable data service units (DSUs), the Cisco uBR924, and the Cisco uBR904
Restrictions
Using the Cisco uBR-MC28C cable modem card:
•Requires a network processing engine (NPE) 200 or higher in a Cisco uBR7200 series chassis
Note If you are using a Cisco uBR7246 VXR chassis, the chassis must contain an NPE-300.
•Requires 128 Megabytes dynamic random-access memory (DRAM)
•Requires Cisco IOS Release 12.1(3a)EC1 or later release
•Excludes support of international channel plans or EuroDOCSIS Annex A RF operations
•Excludes hardware-based spectrum management capabilities found in the Cisco uBR-MC16S cable modem card
Related Features and Technologies
Features that can be used with the Cisco uBR-MC28C cable modem card include:
•Software-based spectrum management introduced in Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1, or Cisco IOS Release 12.0(6)SC, as well as the dynamic upstream modulation feature introduced in Cisco IOS Release 12.1(3a)EC1. To view the Dynamic Upstream Modulation feature module, refer to:
http://www.cisco.com/univercd/cc/td/doc/product/cable/cab_r_sw/spec_mgt.htm•Hot Standby 1+1 Redundancy feature introduced in Cisco IOS Release 12.1(3a)EC; To view this feature module, refer to:
http://www.cisco.com/univercd/cc/td/doc/product/cable/cab_r_sw/hccpfeat.htmRelated Documents
For other information on Cisco uBR7200 series cable modem cards, refer to the following documents:
•Cisco uBR7200 Series Cable Modem Card Hardware Installation Guide
•Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
•Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide
•Cisco Broadband Cable and Fixed Wireless Command Reference Guide
•Cisco uBR7200 series software release notes and feature modules
Supported Platforms
All current Cisco uBR7200 series universal broadband routers support the Cisco uBR-MC28C cable modem card. These include:
•Cisco uBR7223
•Cisco uBR7246
•Cisco uBR7246 VXR
Supported Standards, MIBs, and RFCs
Standards
•DOCSIS ITU J.112 standard and ITU J.83 Annex B
•CableLabs ECR; RFI-R-98036
MIBs
•All earlier Cisco uBR7200 series MIBs
Note Refer to the Cisco MIB web site on CCO at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
for MIB listings and descriptions.
•The OLD-CISCO-CHASSIS-MIB and the ENTITY MIB are updated to enable the Simple Network Management Protocol (SNMP) Manager to correctly identify the Cisco uBR-MC28C domain sets; the OLD-CISCO-CHASSIS-MIB and ENTITY MIB contain cardTable, cardIfIndexTable, entPhysicalTable, entAliasMapping Table, and entPhysicalContainsTable objects that are updated.
RFCs
•All earlier Cisco uBR7200 series RFCs
Note No new or modified RFCs are introduced with this card.
Prerequisites
Before you configure the Cisco uBR-MC28C cable modem card:
•Ensure that your network is designed to support reliable broadband data transmission; at minimum, your network must include:
–Computer on the WAN side of your Cisco uBR7200 series configured as a Dynamic Host Configuration Protocol (DHCP) server to assign IP addresses to cable modems on the cable plant
–Required headend or distribution hub equipment, based on the services to be offered
–Cisco uBR7200 series-compatible external downconverter/upconverter installed in the data path between the Cisco uBR-MC28C cable modem card and the combiner or optical receiver
Note This refers to all cables, amplifiers, and taps at the headend or cable distribution center that connect the Cisco uBR7200 series to the cable plant. Refer to instructions in the Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide located at:
http://www.cisco.com/univercd/cc/td/doc/product/cable/cab_rout/cr72hig/index.htm
•Complete a basic configuration of the Cisco uBR7200 series; this includes, at a minimum, the following tasks:
–Configure a host name and password for the Cisco uBR7200 series.
–Configure the Cisco uBR7200 series to support the Internet Protocol (IP).
–Install and configure at least one port adapter to provide backbone connectivity.
–Install at least one Cisco uBR-MC28C cable modem card in the appropriate slot of the Cisco uBR7200 series chassis; a Cisco cable modem card serves as the RF interface, connecting to an external downconverter/upconverter.
–Follow the basic steps in the Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide that involve bringing up the router; refer to:
http://www.cisco.com/univercd/cc/td/doc/product/cable/cab_rout/cr72scg/index.htm•Define your spectrum based on your channel plan and your cable plant, following general spectrum management configuration guidelines in the Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide or the Cisco IOS Release 12.1(3a)EC1 Cisco uBR7200 Series Dynamic Upstream Modulation feature module.
Configuration Tasks
To configure the Cisco uBR-MC28C cable modem card, perform the following tasks:
•Designate the downstream center frequency for each of the two MAC domains that reflect the digital carrier frequency for the downstream RF carrier—the channel—for that downstream port; do this for both downstream ports.
Note Enter the fixed center frequency for your downstream RF carrier in Hz. This value is informational only. The external downconverter/upconverter actually sets the frequency. Noting the correct value for the cable modem card, however, provides useful troubleshooting information.
•For the first MAC domain:
–Activate the downstream port on the cable modem card.
–Set each of the four upstream port frequencies associated with that downstream.
–Activate each upstream port.
•For the second MAC domain:
–Activate the second downstream port.
–Set each of the four upstream port frequencies associated with the second downstream.
–Activate each upstream port.
Note The Cisco uBR-MC28C cable modem card supports multiple modulation profiles. The card ships from the Cisco factory with modulation profile #1 set. For information on modulation profiles, refer to the Cisco IOS Release 12.1(3a)EC1 Cisco uBR7200 Series Dynamic Upstream Modulation feature module.
Configuring the Cisco uBR-MC28C Cable Modem Card
Follow Step 1 through Step 7 for the second MAC domain. Save your settings to nonvolatile random access memory (NVRAM) to ensure that the system retains the settings after a power cycle:
Router# copy running startVerifying Your Settings
To verify your settings, enter the show running-config command:
Router# show running-configVerifying Upstream Settings
To verify upstream settings, enter the show contr command:
Router# show contr c4/0Interface Cable4/0Hardware is MC28C(F-connector)BCM3210 revision=0x56B2idb 0x6158A4CC MAC regs 0x3E104000 PLX regs 0x3E000000rx ring entries 1024 tx ring entries 128 MAP tx ring entries 128Rx ring 0x4B09CCC0 shadow 0x615A7E78 head 0Tx ring 0x4B09ED00 shadow 0x615A8EE8 head 6 tail 6 count 0MAP Tx ring 0x4B09F140 shadow 0x615A9358 head 16 tail 16 count 0MAP timer sourced from slot 4throttled 0 enabled 0 disabled 0Rx:spurious 0 framing_err 0 hcs_err 0 no_buffer 0 short_pkt 0no_enqueue 0 no_enp 0 miss_count 0 latency 0invalid_sid 0 invalid_mac 0 bad_ext_hdr_pdu 0 concat 0 bad-concat 0Tx: full 0 drop 0 stuck 0 latency 0MTx:full 0 drop 0 stuck 0 latency 96Slots 0 NoUWCollNoEngy 0 FECorHCS 4 HCS 4Req 28448325 ReqColl 0 ReqNoise 23 ReqNoEnergy 28448302ReqData 0 ReqDataColl 0 ReqDataNoise 0 ReqDataNoEnergy 0Rng 0 RngColl 0 RngNoise 0FECBlks 4 UnCorFECBlks 4 CorFECBlks 0MAP FIFO overflow 0, Rx FIFO overflow 0, No rx buf 0Bandwidth Requests= 0x0Piggyback Requests= 0x0Ranging Requests= 0x0Timing Offset = 0x0Bad bandwidth Requests= 0x0No MAP buffer= 0x0Cable4/0 Downstream is upFrequency 576.0000 MHz, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 MspsFEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4Downstream channel ID:1Cable4/0 Upstream 0 is upFrequency 35.184 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 MspsSpectrum Group 2SNR - UnknownNominal Input Power Level 0 dBmV, Tx Timing Offset 0Ranging Backoff automatic (Start 0, End 3)Ranging Insertion Interval 100 msTx Backoff Start 0, Tx Backoff End 4Modulation Profile Group 1Concatenation is enabledpart_id=0x3137, rev_id=0x03, rev2_id=0xFFnb_agc_thr=0x0000, nb_agc_nom=0x0000Range Load Reg Size=0x58Request Load Reg Size=0x0EMinislot Size in number of Timebase Ticks is = 8Minislot Size in Symbols = 64Bandwidth Requests = 0x0Piggyback Requests = 0x0Invalid BW Requests= 0x0Minislots Requested= 0x0Minislots Granted = 0x0Minislot Size in Bytes = 16Map Advance (Dynamic) :2180 usecsUCD Count = 288Cable4/0 Upstream 1 is upFrequency 20.400 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 MspsSpectrum Group 1SNR - UnknownNominal Input Power Level 0 dBmV, Tx Timing Offset 0Ranging Backoff automatic (Start 0, End 3)Ranging Insertion Interval 100 msTx Backoff Start 0, Tx Backoff End 4Modulation Profile Group 1Concatenation is enabledpart_id=0x3137, rev_id=0x03, rev2_id=0xFFnb_agc_thr=0x0000, nb_agc_nom=0x0000Range Load Reg Size=0x58Request Load Reg Size=0x0EMinislot Size in number of Timebase Ticks is = 8Minislot Size in Symbols = 64Bandwidth Requests = 0x0Piggyback Requests = 0x0Invalid BW Requests= 0x0Minislots Requested= 0x0Minislots Granted = 0x0Minislot Size in Bytes = 16Map Advance (Dynamic) :2180 usecsUCD Count = 280Cable4/0 Upstream 2 is upFrequency 18.800 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 MspsSpectrum Group 1SNR - UnknownNominal Input Power Level 0 dBmV, Tx Timing Offset 0Ranging Backoff automatic (Start 0, End 3)Ranging Insertion Interval 100 msTx Backoff Start 0, Tx Backoff End 4Modulation Profile Group 1Concatenation is enabledpart_id=0x3137, rev_id=0x03, rev2_id=0xFFnb_agc_thr=0x0000, nb_agc_nom=0x0000Range Load Reg Size=0x58Request Load Reg Size=0x0EMinislot Size in number of Timebase Ticks is = 8Minislot Size in Symbols = 64Bandwidth Requests = 0x0Piggyback Requests = 0x0Invalid BW Requests= 0x0Minislots Requested= 0x0Minislots Granted = 0x0Minislot Size in Bytes = 16Map Advance (Dynamic) :2180 usecsUCD Count = 276Cable4/0 Upstream 3 is downFrequency not set, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 MspsSpectrum Group 1SNR - UnknownNominal Input Power Level 0 dBmV, Tx Timing Offset 0Ranging Backoff automatic (Start 0, End 3)Ranging Insertion Interval 100 msTx Backoff Start 0, Tx Backoff End 4Modulation Profile Group 1Concatenation is enabledpart_id=0x3137, rev_id=0x03, rev2_id=0xFFnb_agc_thr=0x0000, nb_agc_nom=0x0000Range Load Reg Size=0x58Request Load Reg Size=0x0EMinislot Size in number of Timebase Ticks is = 8Minislot Size in Symbols = 64Bandwidth Requests = 0x0Piggyback Requests = 0x0Invalid BW Requests= 0x0Minislots Requested= 0x0Minislots Granted = 0x0Minislot Size in Bytes = 16Map Advance (Dynamic) :2180 usecsUCD Count = 0Verifying Downstream Center Frequency
To verify the downstream center frequency of each domain, enter the show controllers cable slot/port downstream command:
Router# show controllers cable 4/0 downstreamCable4/0 Downstream is upFrequency 576.0000MHz, Channel Width 6MHz, 64-QAM, Symbol Rate5.056941 MspsFEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4Downstream channel ID: 0Command Reference
Command reference pages are included for the following configuration commands:
•cable downstream if-output
•cable downstream interleave-depth
•cable downstream modulation
•cable downstream rate-limit
•cable insertion-interval
•cable intercept
•cable modulation profile
•cable qos profile
•cable upstream admission-control
•cable upstream channel-width
•cable upstream concatenation
•cable upstream data-backoff
•cable upstream differential-encoding
•cable upstream fec
•cable upstream fec-strength
•cable upstream freq-adj averaging
•cable upstream frequency
•cable upstream minislot-size
•cable upstream modulation
•cable upstream modulation-profile
•cable upstream power-adjust
•cable upstream power-level
•cable upstream range-backoff
•cable upstream rate-limit
•cable upstream scrambler
•cable upstream shutdown
•cable upstream timing-adjust
cable downstream frequency
To have the downstream center frequency reflect the digital carrier frequency of the downstream RF carrier for that downstream port, use the cable downstream frequency command in cable interface configuration mode.
cable downstream frequency down-freq-hz
Syntax Description
Defaults
Disabled
Command Modes
Cable interface configuration
Command History
Usage Guidelines
The downstream frequency is an information-only parameter. The configuration controlling the actual digital carrier frequency is set by the external upconverter. The display parameter you set for a Cisco uBR7200 cable modem card should match the digital carrier frequency you set when you configure the upconverter. The cable downstream frequency command has no effect on the external upconverter; it is informational only.
Examples
The following example shows how to set the downstream center frequency value:
router(config-if)# cable downstream frequency 96000000
cable downstream if-output
To activate a downstream port on a cable modem card for digital data transmissions over the cable plant, use the cable downstream if-output command in cable interface configuration mode. To disable the intermediate frequency (IF) carrier, use the no form of this command.
cable downstream if-output
no cable downstream if-output
Syntax Description
This command has no arguments or keywords.
Defaults
Downstream carrier is enabled
Command Modes
Cable interface configuration
Command History
Usage Guidelines
Caution Disabling the IF output mutes the IF output signal of the Cisco uBR700 series. The upconverter may then change to an alarm state. Cable modems that are connected to that plant segment may be disconnected from the network.
Examples
The following example shows how to enable downstream port 0 on a cable modem card installed in slot 6 of a Cisco uBR7200 series:
router(config-if)# cable 6/0 cable downstream if-output
cable downstream interleave-depth
To set the downstream interleave depth, use the cable downstream interleave-depth command in cable interface configuration mode. To restore the default setting, use the no form of this command.
cable downstream interleave-depth {8 | 16 | 32 | 64 | 128}
no cable downstream interleave-depth
Syntax Description
Defaults
The cable downstream interleave-depth default value is 32.
Command Modes
Cable interface configuration
Command History
Usage Guidelines
This command sets the minimum latency for the system. A higher interleave depth provides more protection from bursts of noise on the Hybrid Fiber Coax (HFC) system. A higher depth, however, also increases downstream latency which slows TCP/IP throughput in some configurations. Table 3 shows interleave characteristics and relationships. The command applies to Cisco "C-based" cable modem cards and the Cisco uBR-MC16S. The command does not apply to the Cisco uBR-MC16E.
Caution Low interleave depth values typically cause some packet loss on HFC networks, because burst noise lasts beyond the forward error correction (FEC) block correctable length. Changing the interleave depth disconnects all connected cable modems on that plant segment.
Table 3 Interleave Characteristics and Relationships
Examples
The following example shows how to set the downstream interleave depth to 128 microseconds:
router(config-if)# cable downstream interleave-depth 128
cable downstream modulation
To set the modulation format for a downstream port on a cable modem card, use the cable downstream modulation command in cable interface configuration mode.
cable downstream modulation {64qam | 256qam}
Syntax Description
64qam
Modulation rate is 6 bits per downstream symbol.
256qam
Modulation rate is 8 bits per downstream symbol.
Defaults
The cable downstream modulation default is 64qam.
Command Modes
Cable interface configuration
Command History
Usage Guidelines
Downstream modulation defines the speed in bits per second at which data travels downstream to the cable modem. A symbol is the basic unit of modulation; 64 QAM encodes 6 bits per symbol; 256 QAM encodes 8 bits per symbol.
Note Setting a downstream modulation format of 256 QAM requires approximately a 6 dB higher signal-to-noise ratio (SNR) than 64 QAM at the subscriber's cable modem. If your network is marginal or unreliable at 256 QAM, use the 64 QAM format instead.
Caution Changing the modulation format disconnects all connected cable modems.
Examples
The following example shows how to set the downstream modulation to 256 QAM from the default of 64 QAM:
router(config-if)# cable downstream modulation 256qam
cable downstream rate-limit
To enable DOCSIS rate limiting on downstream traffic, use the cable downstream rate-limit command in cable interface configuration mode. To disable DOCSIS rate limiting on downstream traffic, use the no form of this command.
cable downstream rate-limit [token-bucket [[shaping [granularity msec | max-delay msec]] | weighted-discard] [exp-weight]
no cable downstream rate-limit
Syntax Description
Defaults
The default value is token-bucket
Command Modes
Cable interface configuration
Command History
Release Modification11.3(6) NA
This command was introduced.
12.0(4)XI
The shaping keyword was added.
12.0(5)T1, 12.1(1)EC1
Support for shaping was added.
Usage Guidelines
When you enter this command without an option, the token-bucket option is used.
Examples
The following example shows how to apply the token-bucket filter algorithm:
router(config-if)# cable 6/0 cable downstream rate-limit token-bucket
cable insertion-interval
To configure the interval between consecutive initial ranging slots on an upstream, use the cable insertion-interval interface configuration command. To configure the automatic setting and ignore any minimum or maximum time settings, use the no form of this command.
cable insertion-interval [fixed-inrvl | automatic [min-intrvl | max-intrvl]]
no cable insertion-interval
Syntax Description
Defaults
The default for the insertion interval is automatic. This setting dynamically varies the frequency of initial ranging upstream slots between 50 milliseconds to 2 seconds.
Command Modes
Cable interface configuration
Command History
Release Modification11.NA
This command was introduced.
12.1 T
This command was modified to adjust the algorithm.
Usage Guidelines
Use this command to specify the minimum and maximum duration between initial ranging opportunities that appear in MAP messages the Cisco uBR7200 series sends. MAP messages define the precise time intervals for cable modems.
The default insertion interval setting (automatic) configures the Cisco uBR7200 series to automatically vary the initial ranging times available to new cable modems that attempt to join the network between 50 milliseconds and 2 seconds.
Use the automatic keyword with this command when you have to bring a large number of cable modems online (for example, after a major power failure). Override the automatic keyword by specifying an insertion interval.
Examples
The following example shows how to specify automatic insertion intervals:
router(config-if)# cable insertion-interval automatic
The following example shows how to specify minimum insertion interval to 100 ms:
Router(config-if)# cable insertion-interval min 100
Related Commands
Command
Description
Specifies automatic or fixed start and stop values for data backoff.
Specifies automatic or configured initial ranging backoff calculation.
cable intercept
To allow the CMTS to forward all traffic to and from a particular cable modem to a data collector located at particular User Datagram Protocol (UDP) port, use the cable intercept command cable interface configuration command. To deactivate this function, use the no form of this command.
cable intercept [mac-address] ip-address udp-port
no cable intercept
Syntax Description
mac-address
Specifies the MAC address.
ip-address
Specifies the IP address.
udp-port
Specifies the destination UDP port number for the intercept stream. Valid range is 0 to 65,535.
Defaults
Disabled
Command Modes
Cable interface configuration
Command History
Release Modification12.0(5)T1
This command was introduced on the T train.
12.0(6)SC
This command was introduced on the SC train.
12.1(2)EC
This command was introduced on the EC train.
Usage Guidelines
When this command is activated, the Cisco uBR7200 series universal broadband router examines each packet for the desired MAC address. When a matching MAC address is found for either the origination or destination endpoint, a copy of the packet is encapsulated into a UDP packet. The packet is then sent to the specified server at the given IP address and port.
Note This command can be used only in the Cisco uBR700 series universal broadband router configuration. It requires maximum privilege to set. The system at ip-address on the udp-port must be configured to listen for and capture the necessary data stream. An IP route to the specified ip-address must exist, and IP connectivity to that device must be present for the traffic to be captured.
This command can be used to comply with the United States Federal Communications Assistance for Law Enforcement Act (CALEA) and other law enforcement wiretap requirements for voice communications.
Examples
The following command shows how to specify the destination IP address and UDP port number for the Cisco uBR7200 series universal broadband router:
(config-if)# cable intercept 0080.fcaa.aabb 3.12.13.8 512
cable modulation-profile
To define the modulation profile, use the cable modulation-profile global configuration command. Use the no form of this command to remove the specified modulation profile.
cable modulation-profile profile iuc fec-tbytes fec-len burst-len guard-t mod scrambler seed diff pre-len last-cw uw-len
no cable modulation-profile profile iuc fec-tbytes fec-len burst-len guard-t mod scrambler seed diff pre-len last-cw uw-len
Syntax Description
Defaults
Modulation profile #1 with the qpsk option is the default.
Command Modes
Global configuration
Command History
Usage Guidelines
A modulation profile is a collection of six burst profiles that are sent out in an Upstream Channel Descriptor (UCD) message to configure a cable modem's transmit parameters for the following upstream message types: request, initial maintenance, station maintenance, short grant, and long grant.
For Cisco cable modem cards other than the Cisco uBR-MC11 FPGA and the Cisco uBR-MC16B, you can use the no cable modulation-profile command to remove all modulation profiles except modulation profile 1. In the case of modulation profile 1, the no cable modulation-profile command sets all of the parameters in a burst to default values.
Note Changes to modulation profiles cause changes to the physical layer. Because changing physical layer characteristics affects router performance and function, this command should be reserved for expert users.
Tips To use this command correctly, enter a line with all parameters for each upstream burst type.
Caution An incomplete burst profile causes unreliable operation or loss of modem connectivity.
Turning the scrambler off might cause packet loss; recommended only in lab testing environments.
Errors or incompatible configurations in burst profiles can cause cable modems to drop connectivity, drop short or long data packets, or even to fail to connect to the network.You can build a burst profile set for which a DOCSIS receiver cannot receive the modem's transmission.
The 160 Ksymbol/sec and 2560 Ksymbol/sec data rates are highly sensitive to unique word length, preamble length, and FEC sizing. Incorrect choices for these values can cause poor, or no, connectivity at these symbol rates.
Examples
The following example shows how to define the burst parameters for profile 2 as follows:
The request burst 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. The remaining initial, station, short, and long bursts are defined in similar fashion for profile 2.
Router(config)# cable modulation-profile 2 request 0 16 1 8 qpsk scrambler 152 no-diff 64 fixed uw8Router(config)# cable modulation-profile 2 initial 5 34 0 48 qpsk scrambler 152 no-diff 128 fixed uw16
Router(config)# cable modulation-profile 2 station 5 34 0 48 qpsk scrambler 152 no-diff 128 fixed uw16
Router(config)# cable modulation-profile 2 short 6 75 6 8 16qam scrambler 152 no-diff 144 fixed uw8
Router(config)# cable modulation-profile 2 long 8 220 0 8 16qam scrambler 152 no-diff 160 fixed uw8
Note You must create all of the bursts (request, initial, station, short and long) for this modulation profile, using the modulation profile command.
Related Commands
cable qos profile
To configure a quality of service (QoS) profile, use the cable qos profile command in global configuration mode. To either set default values for profile group numbers 1 or 2, or to remove the QoS profile if no specific parameters remain, use 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}}
Syntax Description
Defaults
No default behavior or values.
Command Modes
Global configuration
Command History
Examples
The following example shows how to configure QoS profile 4 with a guaranteed upstream rate of 8 kbps, maximum transmission burst of 16 minislots, maximum downstream rate of 128 kbps, a priority of 4, cable baseline privacy set, and a tos-overwrite mask and value byte (in hex) of 0x2:
router(config)# cable qos profile 4 guaranteed-upstream 8
router(config)# cable qos profile 4 max-burst 16
router(config)# cable qos profile 4 max-downstream 128
router(config)# cable qos profile 4 privacy
router(config)# cable qos profile 4 priority 4
router(config)# cable qos profile 4 tos-overwrite 0xA0 0xE0
Related Commands
Command Descriptioncable qos permission
Specifies permission for updating the cable router QoS table.
show cable qos profile
Displays cable router QoS profiles.
cable upstream channel-width
To specify an upstream channel width for an upstream port, use the cable upstream channel-width command in cable interface configuration mode. To set the channel width back to the default setting of 1600,000 Hz, use the no form of this command.
cable upstream usport channel-width first-choice-width [last-choice-width]
no cable upstream usport channel-width
Syntax Description
Defaults
1,600,000 Hz
Command Modes
Cable interface configuration
Command History
Release Modification11.3(5)NA
This command was introduced.
12.0(4)XI
The last-choice-width argument was added.
12.0(7)XR2
The command was updated to support the Cisco uBR-MC16S.
Usage Guidelines
The last-choice-width parameter is supported only by the Cisco uBR-MC16S cable modem card. When the Cisco uBR-MC16S is installed, the system attempts to increase the channel width from the first-choice-width value to the last-choice-width value one step at a time.
Examples
The following example configures upstream port 2 with a channel width of 200,000 Hz (which is equivalent to a symbol rate of 160 kilosymbols/second):
router(config-if)# cable upstream 2 channel-width 200000
The following example configures upstream port 3 to step from a channel width of 1,600,000 Hz to a channel width of 3,200,000 Hz in increments of 200,000 Hz:
router(config-if)# cable upstream 3 channel-width 1600000 3200000
Related Commands
cable upstream concatenation
To turn concatenation on or off from the CMTS, use the cable upstream concatenating cable interface configuration command. To turn off concatenation, use the no form of this command.
cable upstream n concatenation
no cable upstream n concatenation
Syntax Description
Defaults
On
Command Modes
Cable interface configuration
Command History
Usage Guidelines
Concantenation is part of DOCSIS 1.0 extension support. Concatenation must be supported at both the CMTS and the CM.
DOCSIS concatenation combines multiple upstream packets into one packet to reduce packet overhead and overall latency, and increase transmission efficiency. Using concatenation, a DOCSIS cable modem needs to make only one bandwidth request for a concatenated packet, compared to making bandwidth requests for each individual packet. This technique is especially effective for bursty real-time traffic such as voice calls. Concatenation support improves upstream per cable modem (CM) data throughput.
The current Cisco uBR7200 series cable modem card driver can only receive one MAC frame in a data burst. Thus, the CM must make explicit bandwidth requests for every packet it wishes to send upstream. This limits the maximum upstream data throughput a CM receives due to the inherent request-to-grant round-trip latency of the HFC system incurred by every packet. To increase this per-CM upstream throughput, the Cisco uBR7200 driver has been enhanced to receive a concatenated burst of multiple MAC frames from the same CM.
Note Concatenation is supported only on Cisco cable modem cards that are fully DOCSIS-compliant—"C based" cable modem cards and the Cisco uBR-MC16S. The cable modem must also support the DOCSIS 1.0 extensions.
cable upstream data-backoff
To specify automatic or fixed start and stop values for the data backoff, use the cable upstream data-backoff command in cable interface configuration mode. To use the default data backoff values, use the no form of this command.
cable upstream usport data-backoff {automatic | start end}
no cable upstream usport data-backoff
Syntax Description
Defaults
automatic
Command Modes
Cable interface configuration
Command History
Usage Guidelines
The DOCSIS-specified method of contention resolution for cable modems used to send data or requests on the upstream channel is a truncated binary exponential back-off with the initial backoff window and the maximum backoff window controlled by the CMTS. The Cisco uBR7200 series router specifies back-off 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 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.
Cisco recommends that you use the automatic settings for data backoff.
Examples
The following example shows how to set the automatic data backoff values for port 2:
router(config-if)# cable upstream 2 data-backoff automatic
Related Commands
Command
Description
Specifies automatic or configured initial ranging backoff calculation.
cable insertion-interval
Configures the interval between consecutive initial ranging slots on an upstream.
cable upstream differential-encoding
To enable differential encoding on upstream traffic to a specified cable interface, use the cable upstream differential-encoding command in cable interface configuration mode. To disable this function, use the no form of this command.
cable upstream usport differential-encoding
no cable upstreamusport differential-encoding
Syntax Description
Defaults
Enabled
Command Modes
Cable interface configuration
Command History
Usage Guidelines
To verify whether or not 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 is displayed in the show running-config output. If upstream differential encoding is disabled, no differential encoding entry is displayed in the output.
If you are having trouble, make sure that 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; and you selected a valid frequency for your router.
Examples
The following example shows how to enable differential encoding for upstream port 2:
Router(config-if)# cable upstream 2 differential-encoding
cable upstream fec
To enable upstream forward error correction (FEC), use the cable upstream fec command in cable interface configuration mode. To disable FEC, use the no form of this command.
cable upstream usport fec
no cable upstream usport fec
Syntax Description
Defaults
Enabled
Command Modes
Cable interface configuration
Command History
Usage Guidelines
The Cisco uBR7200 series uses forward error correction (FEC) to attempt to correct any upstream data that might have been corrupted. To use this feature, activate FEC on the upstream RF carrier. When FEC is activated, the Cisco uBR7200 series commands all cable modems on the network to activate FEC.
Examples
The following example shows how to activate upstream forward error correction:
router (config-if)# cable upstream 0 fec
Related Commands
cable upstream fec-strength
To override the forward error correction (FEC) setting specified in the modulation profile for this upstream channel, use the cable upstream fec-strength command in cable interface configuration mode. To restore the default value, use the no form of this command.
cable upstream usport fec-strength t-bytes
no cable upstream usport fec-strength
Syntax Description
Defaults
No default behavior or values.
Command Modes
Cable interface configuration
Command History
Examples
The following example shows how to configure the cable upstream fec-strength command:
router(config-if)# cable upstream 2 fec-strength 3
Related Commands
cable upstream freq-adj averaging
To control power adjustments on a Cisco uBR7200 series by setting the frequency threshold, use the cable upstream freq-adj averaging interface configuration command. To disable power adjustments, use the no form of this command.
cable upstream n freq-adj averaging % of frequency adjustment
no cable upstream freq-adj averaging
Syntax Description
Defaults
No default behavior or values.
Command Modes
Interface configuration
Command History
Examples
The following example shows how to change the power adjustment method when the frequency adjustment packet count reaches 50 percent:
Router(config-if)#
cable upstream 0 freq-adj averaging 50Related Commands
cable upstream frequency
To enter a fixed frequency of the upstream radio frequency (RF) carrier for an upstream port, use the cable upstream frequency command in cable interface configuration mode. To restore the default value for this command, use the no form of this command.
cable upstream usport frequency up-freq-hz
no cable upstream usport frequency up-freq-hz
Syntax Description
Defaults
Dynamic (not fixed frequency)
Command Modes
Cable interface configuration
Command History
Usage Guidelines
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 an upstream channel frequency, you may:
•Configure a fixed frequency between 5 to 42 MHz for NTSC channel plans and enable the upstream port, or
•Create a global spectrum group, assign the interface to it, and enable the upstream port.
To configure the default upstream frequency (which is no fixed frequency), enter the cable upstream usport frequency command without specifying a center frequency.
Examples
The following example shows how to configure the upstream center frequency for port 0, located in slot 6, to 5,700,000 Hz:
Router(config-if)# cable upstream 0 frequency 5700000
The following example shows how to allow the Cisco uBR7200 series to dynamically specify a center frequency for the upstream port 0:
Router(config-if)# cable upstream 0 frequency
cable upstream minislot-size
To specify the minislot size (in ticks) for a specific upstream interface, use the cable upstream minislot-size command in cable interface configuration mode. To set the default minislot size of 8 if this is valid for the current channel width setting, use the no form of this command.
cable upstream usport minislot-size size
no cable upstream usport minislot-size
Syntax Description
Defaults
The default settings vary, depending on the specified minislot sizes. The minislot size has a range of values between 2 and 128 and default values for these minislot sizes range between 4 and 64.
Command Modes
Cable interface configuration
Command History
Usage Guidelines
Caution Using values of 64 or 128 for higher symbol rates such as 1280 kilosymbols/second or 2560 kilosymbols/second can cause performance problems. Depending on your current setting's symbol rate, you should select the minislot size (in ticks) that yields a minislot size of 32 or 64 symbols.
Examples
The following example shows how to set the minislot size on upstream port 4 to 16 (or 256 symbols):
router(config-if)# cable upstream 4 minislot-size 16
cable upstream modulation-profile
To assign a modulation profile to an interface, use the cable upstream modulation-profile interface configuration command. Use the no form of this command to assign the default primary modulation profile (profile #1) to the interface.
cable upstream n modulation-profile primary-profile-number secondary-profile-number
no cable upstream n modulation-profile primary-profile-number secondary-profile-number
Syntax Description
n
Port number on the cable modem slot.
primary-profile number
Default modulation profile added to the interface.
secondary-profile number
Additional modulation profile added to the interface.
Defaults
Primary modulation profile (profile #1).
Command Modes
Interface configuration
Command History
Release Modification11.3 NA
This command was first introduced.
12.0(7)XR2
This command was used.
12.1(3a)EC1
This command was modified to add the primary-profile-number and secondary-profile-number.
Usage Guidelines
You can configure modulation profiles with fixed upstream frequencies or on interfaces with assigned spectrum groups. The dynamic upstream modulation feature uses modulation profiles to track upstream signal quality. It checks that the upstream signal can support the configured modulation scheme, and adjusts to a more robust modulation scheme, if necessary. When return path conditions improve, it returns the upstream channel to the higher modulation scheme.
Examples
The following example shows how to assign the primary modulation profile 2 and the secondary modulation profile 1 to port (interface) 0:
Router(config-if)# cable upstream 0 modulation-profile 2 1
cable upstream power-adjust
To control power adjustment methods on the Cisco uBR7200 series, use the cable upstream power-adjust command in interface configuration mode. To disable power adjustments, use the no form of this command.
cable upstream n power-adjust [continue] [noise % of power adjustment] [threshold #]
no cable upstream power-adjust
Syntax Description
Defaults
No default behavior or values.
Command Modes
Interface configuration
Command History
Examples
The following example shows how to change the power adjustment method when the percentage of power adjustment packets reaches 50 percent:
router(config-if)# cable upstream 0 power-adjust noise 50
Related Commands
cable upstream power-level
To set the input power level for the upstream radio frequency (RF) carrier in decibels per millivolt (dBmV), use the cable upstream power-level command in cable interface configuration mode. To restore the default value for this command, use the no form of this command.
cable upstream usport power-level dbmv
no cable upstream usport power-level dbmv
Syntax Description
usport
Specifies the upstream port number.
dbmv
Decibels per millivolt designating the upstream signal input power level. Valid range is -10 dBmV to 25 dBmV.
Defaults
0 dBmV
Command Modes
Cable interface configuration
Command History
Usage Guidelines
The Cisco uBR7200 series controls the output power levels of the cable modems 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 dBmV to 25 dBmV. Higher values cause the modems to increase their transmit power, achieving a greater carrier-to-noise ratio. If your power levels operate at greater than the maximum valid level, you must use an attenuator to bring the power level to within the valid range.
Caution If you increase the input power level, the cable modems on your HFC network increase their transmit power level. This might cause an increase in the carrier-to-noise ratio on the network. Be careful if you adjust this parameter. You might violate the upstream return laser design parameters.
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 modem service on your network will be disrupted. If you decrease the power level by more than 5 dB within 30 seconds, cable modems on your network will be forced offline.
When you run cable upstream 0 power-level, Cisco recommends that the adjacent channel not have a large variation. The recommended maximum input power variance is 5 to 6 dBmV.
Examples
The following example shows how to set the input power level for upstream port 0 to -5 dBmV:
router(config-if)# cable upstream 0 power-level -5
Related Commands
cable upstream range-backoff
To specify automatic or configured initial ranging backoff calculation, use the cable upstream range-backoff command in cable interface configuration mode. To set default values, use the no form of this command.
cable upstream usport range-backoff {automatic | start end}
no cable upstream usport range-backoff
Syntax Description
Defaults
automatic
Command Modes
Cable interface configuration
Command History
Usage Guidelines
The DOCSIS-specified method of contention resolution for cable modems used to send data or requests on the upstream channel is a truncated binary exponential back-off with the initial backoff window and the maximum backoff window controlled by the CMTS. The Cisco uBR7200 series router 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 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.
The automatic setting is optimized for a maximum of 250 cable modems per upstream port. Set manual values for data backoff windows only when operating with more than 250 cable modems per upstream port.
Examples
The following example shows how to set the range backoff to automatic for upstream port 2:
router(config-if)# cable upstream 2 range-backoff automatic
Related Commands
Command
Description
Specifies automatic or fixed start and stop values for data backoff.
cable insertion-interval
Configures the interval between consecutive initial ranging slots on an upstream.
cable upstream rate-limit
To set DOCSIS rate limiting for an upstream port on a cable modem card, use the cable upstream rate-limit command in cable interface configuration mode. To disable DOCSIS rate limiting for the upstream port, use the no form of this command.
cable upstream usport rate-limit [token-bucket [shaping]]
no cable upstream usport rate-limit
Syntax Description
Defaults
Token bucket algorithm with traffic shaping.
Command Modes
Cable interface configuration
Command History
Release Modification11.3(6)NA
This command was introduced.
11.3(9)NA
The shaping keyword was added.
Usage Guidelines
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 Cisco uBR7200 series 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 modem (SID).
When the token-bucket algorithm is configured, the Cisco uBR7200 series automatically drops packets in violation of allowable upstream bandwidth.
Use of the default value (the upstream port's rate limit) enforces strict DOCSIS-compliant rate limiting. Cisco highly recommends to using the default setting of token-bucket with the shaping option.
Examples
The following example shows how to configure the token bucket filter algorithm with traffic shaping on upstream port 4:
router(config-if)# cable upstream 4 rate-limit token-bucket
Related Commands
cable upstream scrambler
To enable the cable upstream scrambler, use the cable upstream scrambler command in cable interface configuration mode. To restore the default configuration value for this command, use the no form of this command.
cable upstream usport scrambler
no cable upstream usport scrambler
Syntax Description
Defaults
Disabled
Command Modes
Cable interface configuration
Command History
Usage Guidelines
This command causes cable modems to enable their pseudo-random scrambler circuitry to improve the robustness of the upstream receiver on the line card.
The scrambler on the upstream radio frequency (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. The upstream scrambler is activated by default and should not be disabled under normal circumstances.
Caution Scrambler must be activated for normal operation. Deactivate only for prototype modems that do not support scrambler.
Examples
The following example shows how to activate the upstream scrambler:
router(config-if)# cable upstream 0 scrambler#
Related Commands
cable upstream shutdown
To disable the upstream port, use the cable upstream shutdown command in cable interface configuration mode. To enable the upstream port, use the no form of this command.
cable upstream usport shutdown
no cable upstream usport shutdown
Syntax Description
Defaults
Upstream port enabled
Command Modes
Cable interface configuration
Command History
Examples
The following example shows how to disable the upstream port:
router(config-if)# cable upstream 0 shutdown
cable upstream timing-adjust
To enable upstream timing adjustment for a specified cable interface, use the cable upstream timing-adjust cable interface configuration command. To return to the default values, use the no form of this command.
cable upstream usport timing-adjust {continue sec | threshold sec}
no cable upstream usport timing-adjust {continue sec | threshold sec}
Syntax Description
Defaults
2 seconds for continue and 1 second for threshold.
Command Modes
Cable interface configuration mode
Command History
Usage Guidelines
To verify whether or not 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 is displayed in the show running-config output.
If you are having trouble, make sure that 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; and you have entered the correct slot and port numbers.
Note The cable timing-adjust command is applicable only on the Cisco 12.1(12)SC and 12.1(3)T Releases. It is deprecated on the 12.1(3a)EC1 Release.
Examples
The following example shows how to set the upstream time adjustment ranging value to 5 seconds:
CMTS01(config-if)# cable upstream 0 time-adjust continue 5
The following example shows how to set the upstream time adjustment threshold value to the default of 12 seconds:
CMTS01(config-if)# cable upstream 0 time-adjust threshold 12