QoS - Trust DSCP on CoS-based Linecard

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Jan 29th, 2014
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How does the switch manage ingress queueing when I configure - trust dscp - on a port of a linecard that supports only cos-based queueing e.g. the WS-X6848-GE-TX on Catalyst 6500?

1) Does the switch ingress queueing according to the incoming CoS value in the packet (given that the packet has a 802.1q tag)

or

2) Does the switch ingress queueing according to the "internal" CoS value it gets from the DSCP-to-CoS map


According to the Catalyst 6500 Configuration Guide - Figure 43-3 - the switch does the queueing based on the incoming CoS value of the packet.

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/qos.html#wp1671507


Can anybody confirm this?

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Jon Marshall Wed, 01/29/2014 - 04:38
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For PFC based QOS -

     

1) yes it does


2) the CoS value determined from the internal DCSP value is, as far as i am aware, only relevant to egress queueing.


Edit - for confirmation see Table 1 in the following link  -


http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd803e5269.html


i am not familiar with QOS on the 6500s using IOS 15.x so there may be differences.


Jon

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