Setting Upstream Traffic Shaping - Cisco 7246VXR - uBR Router Software Configuration Manual

Configuring the Upstream Cable Modem Interface

Setting Upstream Traffic Shaping

Upstream traffic shaping, available on the DOCSIS upstream channel, delays the scheduling of the
upstream packet, which in turn causes the packet to be buffered on the cable customer premises
equipment (CPE) device, instead of being dropped. This allows the user's TCP/IP stack to pace the
application traffic appropriately and approach throughput commensurate with the subscriber's defined
quality of service (QoS) levels.
The CMs are buffered without incurring TCP-related timeouts and retransmits. This enables the CMTS
to enforce the peak upstream rate for each CM, without degrading overall TCP performance for the
subscriber CPEs. Upstream grant shaping is per cable interface (per service ID (SID)).
Token-bucket policing with shaping is the per-upstream default rate-limiting setting at the CMTS.
Shaping can be enabled or disabled for the token-bucket algorithm.
To enable upstream traffic shaping for an upstream port on a Cisco cable interface line card, use one of
the following commands in cable interface configuration mode.
Command
Step 1
Router(config-if)# cable upstream
usport rate-limit
Router(config-if)# cable upstream
usport rate-limit token-bucket
Router(config-if)# cable upstream
usport rate-limit token-bucket
shaping
Step 2
Router(config-if)# ^Z
Router#
To disable upstream traffic shaping for an upstream port, enter the following command in cable interface
configuration mode:
Router(config-if)# no cable upstream usport rate-limit
The software supports:
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Upstream grant shaping is per CM (per service ID (SID)). Shaping can be enabled or disabled for the
Tip
token-bucket algorithm.
Before the introduction of this feature, the CMTS would drop bandwidth requests from a CM it detected
Note
as exceeding its configured peak upstream rate. Such request dropping affects the throughput
performance of IP-based protocols such as FTP, TCP, and Simple Network Management Protocol
(SNMP). With this feature, the CMTS can shape (buffer) the grants for a CM that is exceeding its
upstream rate, rather than dropping the bandwidth requests.
Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
3-26
Purpose
Enables traffic shaping for the specified upstream cable interface.
Enables traffic shaping for the upstream cable interface employing the
token-bucket policing algorithm. With this command the
Cisco uBR7200 series CMTS automatically drops packets in violation of
allowable upstream bandwidth.
Default. Enables traffic shaping for the upstream cable interface employing
the token-bucket policing algorithm with traffic shaping.
Exits back to the EXEC mode so that you can verify upstream traffic shaping.
Generic calendar queuing routines
New token-bucket policing function
Grant shaping application of the calendar queues
Upstream rate-shaping option to the token-bucket keyword
A default state change from 1-second burst policing to token bucket with shaping
Chapter 3 Configuring Cable Modem Interface Features
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