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Chapter 2 Cisco CMTS Configuration Commands
cable upstream fragment-force
cable upstream fragment-force
To specify that a cable interface line card should fragment DOCSIS frames on an upstream when the
frame exceeds a particular size, use the
cable upstream fragment-force
command in cable interface
configuration mode. To disable the forcing of fragmentation, use the
no
form of this command.
cable upstream
n
fragment-force
[
fragment-threshold
[
number-of-fragments
] ]
no cable upstream
n
fragment-force
Syntax Description
Defaults
fragment-threshold
is 2000 bytes and
number-of-fragments
is 3
Command Modes
Interface configuration (cable interface only)
Command History
Usage Guidelines
DOCSIS 1.1 allows the CMTS to fragment DOCSIS frames to improve performance, especially in
networks that combine real-time traffic, such as voice, with data traffic. The
cable upstream
fragment-force
command allows you to specify the size of frames that should be fragmented, as well as
the number of fragments that should be created when fragmenting.
Tip
This command takes effect only when fragmentation has been enabled on the upstream using the
cable
upstream fragmentation
command (which is the default configuration). This command also supercedes
the configuration of the
cable default-phy-burst
command, if necessary.
In the default configuration, the Cisco CMTS fragments DOCSIS frames that are 2,000 bytes or larger
in size, and it fragments these frames into three equally-sized fragments. Do not use a fragment size
greater than 2,000 bytes on the Cisco uBR-MC5X20S/U cable interface line cards, and do not use a
fragment size greater than 3,500 bytes on all other cable interface line cards, unless otherwise instructed
by a Cisco TAC engineer.
n
Specifies the upstream port number. Valid values start with 0 for the first
upstream port on the cable interface line card.
fragment-threshold
Number of bytes for the threshold at which DOCSIS frames are fragmented.
The valid range is 0 to 4000, with a default of 2000 bytes.
number-of-fragments
Number of fragments that the cable interface line card should create when
fragmenting DOCSIS frames. The card attempts to create this many equal-
sized fragments when fragmenting. The valid range is 1 to 10, with a default
of 3 fragments.
Release
Modification
12.2(15)BC2
This command was introduced.
