From: iron_tri (iron_tri@msn.com)
Date: Thu Mar 20 2003 - 01:21:28 GMT-3
The Priority command is used when LLQ (Low Latency Queuing) aka PQ-CBWFQ
is desired.
The Bandwidth command is used for CBWFQ (Class Based Weighted Fair Queuing).
The two can be combined in a policy to ensure that one type of traffic gets
a guaranteed level of service in its own priority queue (LLQ) using the
Priority command, and the other class(es) of traffic receive a predetermined
amount of guaranteed bandwidth using the bandwidth command (CBWFQ). The
following example should help:
Router(config)# policy-map wan_policy
Router(config-pmap)# class Gold
Router(config-pmap-c)# priority 512
Router(config-pmap)# exit
Router(config-pmap)# class Silver
Router(config-pmap-c)# bandwidth 256
Router(config-pmap)# exit
Router(config-pmap)# class class-default
Router(config-pmap-c)# fair-queue 10
In the above example, Gold traffic is configured for LLQ, with a single
Priority Queue and guaranteed bandwidth of 512 Kbps using the Priority
command.
Silver traffic is configured for CBWFQ using the bandwidth command with a
guaranteed bandwidth of 256 Kbps since neither tail drop of WRED congestion
avoidance apply.
The default class is configured with the fair-queue command which enables
WRED congestion avoidance and it also configures 10 dynamic queues for the
default class of traffic. This is traffic not specified or matched by the
Gold or Silver classes.
By the way, if Gold traffic exceeds its mark of 512 kbps, Gold packets get
dropped by the router. Be careful if you are designing for IP Telephony or
VoIP networks. Make sure you spend time with the SP to figure out how you
should be classifying your traffic, and make sure you pay attention to their
QOS mechanisms. One large provider that uses Rate Limiting does not offer
the opportunity to have even the highest levels of traffic re-classified and
sent via a lower queue which is an option with Rate Limiting in a Cisco
environment. Read into that statement dropped voice packets if the high
level traffic exceeds its rate....unhappy voice customers.
Anyway....
HTH,
JP
----- Original Message -----
From: <jim.phillipo@guardent.com>
To: <ccielab@groupstudy.com>
Sent: Wednesday, March 19, 2003 5:26 PM
Subject: QOS Questions
> What is the difference between:
>
> Priority 100 versus Bandwidth 100 under the r1(config-pmap-c)# Mode ?
>
> Jim Phillipo, CCNP, CCDP
> Sr. Internetworking Engineer
> W: 401.456.1821 F: 401.456.0599 M: 508.982.8923
> 90 Royal Little Drive, Providence, RI 02904
> www.guardent.com
> _____________________________________________________
> G U A R D E N T
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