DSCP to CoS mapping: Avaya traffic

Unanswered Question
Oct 17th, 2007
User Badges:

It appears that Avaya marks its voice traffic as follows:

L2 signaling cos 6 L3 signaling dscp 34

L2 audio cod 6 L3 audio dscp 46

Has anyone interacted with theses settings and what are the right mappings for 6500 series Modules?

I am about to use the following:

#mls qos map dscp-cos 34 46 to 6

#mls qos map dscp-cos 48 to 5 "move IP control to cos 5)

#mls qos map cos-dscp 0 8 16 24 32 46 48 56 leave cos to dscp unchanged.

Finally use: #mls qos thrust dscp on input interfaces.

Can anyone clarify?


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
hadbou Tue, 10/23/2007 - 10:54
User Badges:
  • Bronze, 100 points or more

The 6608 and 6624 internal port is treated as trust-cos to the Catalyst 6000. So the default COS-to-DSCP mapping of the cards will determine the DSCP values with which the IP packets are marked unless they are changed in the switch.

The 6608 and 6624 will tag packets as follows:

COS = 5 for rtp traffic

COS = 3 for signalling traffic

By default on the Catalyst 6000, these COS values map in IP packets to DSCP 24 (COS = 3) and 40 (COS = 5) as shown in the table below.

Generally, the recommended DSCP values to use in a VoIP network differ slightly. They are:

DSCP = 46 for rtp traffic (Recommended Expedited Forwarding (EF) value)

COS = 26 for signalling traffic (AF31)

It may be necessary to change the default COS-DSCP mapping on the Catalyst 6000 so that the DSCP markings in packets generated by the 6608 and 6624 cards conform to the network policy. For example, if other devices in the network are marking packets with the recommended values.

Information on how to change the default COS-DSCP mapping is provided in the Mapping Received CoS Values to Internal DSCP Values section of Catalyst 6000 Family Software Configuration Guide.


This Discussion