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cable upstream concatenation
cable upstream concatenation
To enable DOCSIS concatenation at the CMTS, use the cable upstream concatenating command in
cable interface configuration mode. To turn off concatenation, use the no form of this command.
Syntax Description
n
Defaults
Concatenation is enabled
Command Modes
Interface configuration (cable interface only)
Command History
Release
12.0(7)XR2
Usage Guidelines
Concatenation is part of DOCSIS 1.0 extension support. Concatenation provides for improved
bandwidth efficiency but must be supported at both the headend 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 CM 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 CM data throughput. The Cisco CMTS radio frequency
(RF) line card driver can receive only one MAC frame in a data burst. Thus the CM must make explicit
bandwidth requests for every packet it sends upstream. This limits the maximum upstream data
throughput received by the CM due to the inherent request-to-grant round-trip latency of the hybrid
fiber-coaxial (HFC) cable system incurred by every packet. To increase this per-CM upstream
throughput, the Cisco CMTS driver has been enhanced to receive a concatenated burst of multiple MAC
frames from the same CM.
Concatenation is not supported on the Cisco uBR-MC11 FPGA and Cisco uBR-MC16B cable interface
Note
line cards.
Examples
The following example shows how to enable concatenation for CMs on upstream port 2 on the cable
interface in slot 3/0:
router(config)# interface c3/0
router(config-if)# cable upstream 2 concatenation
Cisco Broadband Cable Command Reference Guide
2-294
cable upstream n concatenation
no cable upstream n concatenation
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.
Chapter 2
Cisco CMTS Configuration Commands
OL-1581-08
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