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Chapter 2
Cisco CMTS Configuration Commands
cable upstream fragmentation
To enable fragmentation of DOCSIS frames on a particular upstream, use the cable upstream
fragmentation command in cable interface configuration mode. To disable fragmentation, use the no
form of this command.
Syntax Description
n
Defaults
By default, fragmentation is enabled for all upstream ports on ASIC line cards (Cisco uBR-MC11C,
Cisco uBR-MC12C, Cisco uBR-MC14C, Cisco uBR-MC16C, Cisco uBR-MC16S, and Cisco uBR-
MC28C) and disabled for all upstream ports on old FPGA line cards.
Cisco IOS Release 12.1 CX supports the Multiple Grant Mode of DOCSIS 1.1 fragmentation.
Note
Command Modes
Interface configuration (cable interface only)
Command History
Release
12.1(4)CX
12.2(4)BC1
Usage Guidelines
This command enables and disables DOCSIS layer 2 fragmentation, which reduces run-time jitter
experienced by constant bit rate (CBR) slots on the corresponding upstream. Disabling fragmentation
increases the run-time jitter, but also reduces the fragmentation reassembly overhead for fragmented
MAC frames. For ports running CBR traffic, fragmentation should be enabled (the default).
Note
Do not confuse DOCSIS Layer 2 fragmentation with IP Layer 3 fragmentation.
Examples
The following command shows DOCSIS fragmentation being enabled on upstream 0 on the cable
interface in slot 2/0:
Router# configure terminal
Router(config)# interface c2/0
Router(config-if)# cable upstream 0 fragmentation
Router(config-if)#
OL-1581-08
cable upstream n fragmentation
no cable upstream n fragmentation
Specifies the upstream port number. Valid values start with 0 for the first
upstream port on the cable interface line card.
Modification
This command was introduced.
Support for this command was added to the Release 12.2 BC train.
Cisco Broadband Cable Command Reference Guide
cable upstream fragmentation
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