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The enhancements to the Cisco uBR7246 cable router extend and improve the command line interface (CLI). It supports burst profile, quality of service (QoS), improved parameter configuration, the MC11 modem card, and the MC16 modem card.
Downstream QoS handling is compliant with Multimedia Cable Network System (MCNS) requirements, and upstream QoS handling and Spectrum Management have been improved.
The Cisco uBR7246 now supports multicast authentication via RADIUS, and security has been enhanced for baseline privacy (including MCNS Data Over Cable System Interface Specification (DOCSIS) compliance). Also, this cable router now supports Dynamic Host Configuration Protocol (DHCP) Relay Subscriber ID Insertion.
These enhancements to the Cisco uBR7246 cable router bring value to the digital broadband network by:
Amplifier—Used on coaxial segments of a Community Antenna Television (CATV) plant to restore signal levels lost due to attenuation through distance. Unfortunately, amplifiers amplify noise as well as signal.
Branch Line—A coaxial cable that runs from a trunk line to a subscriber drop point. A branch line is also known as "Feeder Cable."
Cable Modem—Any device which modulates and demodulates digital data onto a CATV plant.
Cable Line Card—Modem front-end card of the cable router headend unit, plugged into the midplane. Each Cable Line Card provides a number of radio frequency (RF) channels as external interfaces.
Cable Router—A modular chassis-based router optimized for the data over CATV hybrid fiber-coaxial (HFC) application.
CATV—Originally Community Antenna Television. Now used to refer to any cable-based (coaxial/fiber) system provision of television services.
CDMTS, CMTS—Cable (Data) Modem Termination System.
Channel—A specific frequency allocation and bandwidth. Downstream channels used for television in the US are 6 MHz wide. In Europe, downstream channel width is 8 MHz.
Combiner Group—The return paths of several fiber nodes can be combined at a single point to form one RF domain. This single point is called a combiner group. See also Spectrum Group.
CPE—Customer Premises Equipment. In the Cable Router application, this will usually be one or multiple PCs located at the customer side.
Distribution Hub—A smaller or remote headend distribution point for a CATV system. Video signals are received here from another site (headend), and redistributed. Sometimes a small number of locally originated signals are added. Such signals might be city information channels, HFC cable modem signals, and so forth.
Downstream—The set of frequencies used to send data from a headend to a subscriber.
Drop—A subscriber access point. The actual coaxial connection in the subscribers home.
Fiber Node, Node—An optical node located in the outside plant distribution system which terminates the fiber-based downstream signal as an electrical signal onto a coaxial RF cable. Each fiber node is defined to support a certain serving area, either defined by number of homes passes or total amplifier cascade (number of active amplifiers in the longest line from the node to the end of the line).
Headend—Central distribution point for a CATV system. Video signals are received here from satellite (either co-located or remote), the frequency is converted to the appropriate channels, combined with locally originated signals, and rebroadcast onto the HFC plant. For a CATV data system, the headend is the typical place to link between the HFC system and any external data networks.
HFC—Hybrid fiber-coaxial. Older CATV systems were provisioned using only coaxial cable. Modern systems use fiber transport from the headend to an optical node located in the neighborhood to reduce system noise. Coaxial cable runs from the node to the subscriber. The fiber plant is generally a star configuration with all optical node fibers terminating at a headend. The coaxial cable part of the system is generally a trunk and branch configuration.
Homes Passed—The number of homes or offices potentially serviceable by a cable system either on a per node or per system basis.
Midsplit—A frequency allocation plan where 5 to 108 MHz is used for upstream data and 178+ MHz is used for downstream data.
Optical Node—A device used to convert broadband RF (for example, television signals) to/from a fiber optic signal. An optical node is typically located in the outside field.
Predator—Code name for the Cisco 7200 class of modular routers that accept PCI bus-based port adapters.
QAM—Modulation scheme mostly used in the downstream direction (QAM-64, QAM-256). QAM-16 is expected to be usable in the upstream direction. Numbers indicate number of code points per symbol. Number of bits per symbol can be computed by 2(number of bits/symbol) = number of code points.
QPSK—Modulation scheme used in the upstream direction. Supports two data bits per symbol.
Spectrum Group—A combiner group can be associated with a frequency hop table. This frequency hop table associated with a combiner group is the spectrum group, as opposed to the RF topology point, which is the combiner group. See also Combiner Group.
Subsplit—A frequency allocation plan where 0 to 42 MHz is used for upstream data and 50+ MHz is used for downstream data.
Tap—A passive device that divides the signal between the trunk or feeder lines and splits the signal into ports for subscriber drop access.
Telephony Return—A variant of a cable data system where the return path from the subscriber cable modem is routed over a dialup (or ISDN) connection instead of over an upstream channel.
Trunk Line—A CATV backbone coaxial cable. This runs from an Optical Node and through a specific neighborhood or serving area.
Upstream—The set of frequencies used to send data from a subscriber to the headend.
This feature is supported on the Cisco uBR7246 router only.
Complete the basic configuration of the Cisco uBR7246 as described in the Cisco uBR7246 Universal Broadband Router Installation and Configuration Guide and the Voice, Video, and Home Applications Configuration Guide.
The Cisco uBR7246 feature enhancements support the Radio Frequency (RF) Interface Management Information Base (MIB). For descriptions of supported MIBs and how to use MIBs, see Cisco's MIB website on Cisco Connection Online (CCO) at the following URL: http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
No RFCs are supported by this feature.
The basic configuration tasks required by this version of the Cisco uBR7246 cable router are the same as those described in the Cisco uBR7246 Universal Broadband Router Installation and Configuration Guide and the Voice, Video, and Home Applications Configuration Guide.
Additional configuration tasks are:
You can configure upstream frequency hop tables using cable spectrum-group commands. Start by determining which upstream ports are assigned to a combiner group. Then apply the following steps to configure a spectrum group:
To configure frequency hopping, apply the following steps:
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 kill 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 line card and modem carrying 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 c3/0, install c4/0 and connect both upstreams together using a combiner. If the upstream frequency of c3/0 is currently 22.4 Mhz, then set c4/0 to 22.4 Mhz while c4/0 is carrying traffic. This should force c3/0 to change the frequency to the next configured value.
The verification tasks required by this version of the Cisco uBR7246 cable router are the same as those described in the Cisco uBR7246 Universal Broadband Router Installation and Configuration Guide and the Voice, Video, and Home Applications Configuration Guide.
To illustrate configuring spectrum groups, assume that an MC16 card is in slot 3 and is named Cable3/0. Its upstream ports are named U0 through U5. You want ports U0 through U3 to belong to one combiner group, and ports U4 and U5 to belong to a different combiner group because of higher subscriber penetration. In both combiner groups, the allocated spectrum should be three 3.2 MHz slots centered at 21.6, 24.8, and 28.0 MHz. The allocated spectrum is 20.0 to 29.6 MHz. From global configuration mode, enter the configure terminal command. Then enter:
Spectrum group 1 will be used for ports U0 through U3. Spectrum group 2 will be used for ports U4 and U5. Because ports U4 and U5 belong to the same combiner group, spectrum group 2 is configured as shared. The shared keyword prevents frequency collision.
To assign the upstream ports to the frequency hop tables for slot 3, enter:
The upstream ports are assigned frequencies from their respective spectrum groups. Ports U0 through U3 will be set to 21.6 MHz. Ports U4 and U5 will be set to 21.6 and 24.8 MHz, respectively.
For additional configuration examples, refer to the Cisco uBR7246 Universal Broadband Router Installation and Configuration Guide and the Voice, Video, and Home Applications Configuration Guide.
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 11.3 command references.
To set the modulation rate for a downstream port on a cable modem card, use the cable downstream modulation cable interface configuration command:
This command first appeared in Cisco IOS Release 11.3 XA.
Downstream modulation defines the modulation type used for downstream traffic. Specifying the symbol rate indirectly influences the interface speed; at 64qam, the interface speed is 6xx bits/second. Specifying 256qam sets the interface speed to 8xx bits/second.
The following example sets the downstream modulation:
To enable Data Over Cable Services Interface Specification (DOCSIS) rate limiting on downstream traffic, use the cable downstream rate-limit interface configuration command. Use the no form of this command to disable DOCSIS rate-limiting on downstream traffic.
cable downstream rate-limit, which enforces strict DOCSIS-complaint rate limiting.
This command first appeared in Cisco IOS Release 11.3(6)NA.When you enter this command without an option, it enables strict DOCSIS-compliant rate limiting, which sets the burst rate to the interface speed.
The following example applies the token bucket filter algorithm:
To specify the number of days to age the cable modem from the flap-list table, use the cable flap-list aging global configuration command. Use the no form of this command to disable this feature.
This command first appeared in Cisco IOS Release 11.3 NA.
A flap list is a table maintained by the Cisco uBR7246 for every modem (active or not) that is having communication difficulties. (Flapping refers to the rapid disconnecting and reconnecting of a cable modem that is having problems holding a connection.) The flap list contains modem MAC addresses and logs the time of the most recent activity. You can configure the size and entry thresholds for the flap list.
The following example specifies that the flap-list table retain two days of performance for this cable modem:
cable flap-list insertion time
cable flap-list size
cable flap-list power-adjust threshold
cable flap-list miss-threshold
clear cable flap-list
To set the insertion time interval, use the cable flap-list insertion-time global configuration command. Use the no form of this command to disable insertion time.
This command first appeared in Cisco IOS Release 11.3 NA. This command controls the operation of a flapping modem detector. When the link establishment rate of a modem is shorter than the period defined by this command, the modem is placed in the flap list.
The following example sets the insertion time interval to 62 seconds:
cable flap-list size
cable flap-list power-adjust threshold
cable flap-list aging
cable flap-list miss-threshold
clear cable flap-list
To specify the power-adjust threshold for recording a flap-list event, use the cable flap-list power-adjust threshold global configuration command. Use the no form of this command to disable power-adjust thresholds.
This command first appeared in Cisco IOS Release 11.3 NA. This command controls the operation of a flapping modem detector. When the power adjustment of a modem exceeds the threshold, the modem is placed in the flap list.
The following example the following command sets the power-adjust threshold to 1:
cable flap-list insertion time
cable flap-list size
cable flap-list aging
cable flap-list miss-threshold
clear cable flap-list
To specify the maximum number of modems reported in the flap-list table, use the cable flap-list size global configuration command. Use the no form of this command to specify the default flap-list table size.
This command first appeared in Cisco IOS Release 11.3 NA.
The following example limits the flap-list table size to no more than 2 modems:
cable flap-list size
cable flap-list power-adjust threshold
cable flap-list aging
cable flap-list miss-threshold
clear cable flap-list
To specify a destination address for User Datagram Protocol (UDP) broadcast (DHCP) packets, use the cable helper-address interface configuration command. Use the no form of this command to disable this feature.
This command first appeared in Cisco IOS Release 11.3 NA. If you specify a secondary interface address, the giaddr field in the DHCP requests will be sent to the primary address for DHCP requests received from cable modems, and to the secondary IP address for DHCP requests received from hosts.
The following example forwards UDP broadcasts from cable modems to the DHCP server at 172.23.66.44:
The following example forwards UDP broadcasts from hosts to the DHCP server at 172.23.66.44:
To set the time between opportunities for cable modems to request a connection from the Cisco uBR7246, use the cable insertion-interval interface configuration command. Use the no form of this command to use the automatic setting and ignore any minimum or maximum time settings.
automatic (dynamically varying the frequency of initial ranging upstream slots between 50 milliseconds to 2 seconds).
This command first appeared in Cisco IOS Release 11.3 NA. Use this command to configure the frequency at which the initial maintenance interval is to appear in MAP messages. MAP messages define the precise time intervals during which modems can transmit.
Use the automatic keyword with this command when you have to bring a lot of modems on line quickly (for example, after a major power failure). Override the automatic keyword by specifying an insertion interval.
The following example specifies the automatic setting:
To specify that IP multicast streams be encrypted, use the cable match address interface configuration command. Use the no form of this command if you do not want to use encryption.
This command first appeared in Cisco IOS Release 11.3 NA. Configure the access list using the ip access-list command.
The following example specifies that the multicast stream defined by the access list named reno be encrypted:
The following example specifies that the multicast stream defined by the access list number 102 be encrypted:
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.
This command first appeared in Cisco IOS Release 11.3 NA.
You can use the no form of this command to remove all modulation profiles except modulation profile 1. In the case of modulation profile 1, the no form of this command sets all of the parameters in a burst to default values.
The following example defines 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.
Note You have to create all of the bursts (request, initial, station, short and long) for this modulation profile to use the modulation profile command.
See Table 5 for a description of the output display fields.
cable upstream modulation-profile
show cable modulation-profile
To enable privacy in the system, use the cable privacy interface configuration command. Use the no form of this command to disable privacy.
This command first appeared in Cisco IOS Release 11.3 NA. While the default for this command is to enable privacy, it is not mandatory.
The following example displays the options available with this command:
The following example forces Baseline Privacy to be used for all modems:
The following example turns on BPI modem authentication:
The following example turns on BPI muticast authorization:
To specify permission for updating the QoS table, use the cable qos permission global configuration command. Use the no form of this command to remove a previously enabled permission.
This command first appeared in Cisco IOS Release 11.3 NA.
The following example enables modems to request arbitrary QoS parameters:
cable qos profile
show cable qos permission
show cable qos profile
To configure a QoS profile, use the cable qos profile global configuration command. Use the no form of this command to either set default values for profile group numbers 1 or 2, or remove the QoS profile if no specific parameters remain.
This command first appeared in Cisco IOS Release 11.3 NA.
The following examples configure QoS profile 4 with guaranteed upstream of 2 kbps, maximum transmission burst of 2, maximum downstream rate of 3 kbps, with a priority of 4, cable baseline privacy set, and a tos-overwrite mask and value byte (in hex) of 0x2:
cable qos permission
show cable qos profile
To enable the system to insert the cable modem MAC address into a DHCP packet received from a modem or host and forward the packet to a DHCP server, use the cable relay-agent-option interface configuration command. Use the no form of this command to disable insertion.
This command has no keywords or arguments.
This command first appeared in Cisco IOS Release 11.3 NA. This functionality enables a DHCP server to identify the user (cable modem) sending the request and initiate appropriate action based on this information.
The following example enables the insertion of DHCP relay agent information into DHCP packets:
To configure authentication and data privacy parameters, use the cable shared-secret interface configuration command. Use the no form of this command to disable authentication during the modem's registration phase.
This command first appeared in Cisco IOS Release 11.3 XA.
The following example activates cable modem authentication, using "3344912349988...sf" as the shared secret key and indicating that an encrypted message follows:
To configure a continuous band setting for a spectrum group, use the cable spectrum-group band global configuration command. Use the no form of this command to delete the band settings for a spectrum group.