From: Bob Sinclair (bsin@cox.net)
Date: Wed Oct 27 2004 - 00:09:40 GMT-3
Andy,
As you say, if you trust CoS, then any unmarked (untagged) traffic will get
the default CoS (0). When that traffic leaves the switch, it will go out
with the DSCP set according to the cos-dscp map. The default cos-dscp map
is as follows:
CoS ->DSCP
0 - 0
1 - 8
2 - 16
3 - 24
4 - 32
5 - 40
6 - 48
7 - 56
So, if it comes in with cos 5, it will go out with DSCP marked to 40, by
default. The Auto-QoS feature changes this map so that cos3 gets mapped to
DSCP 26 (AF31) and cos 5 gets mapped to DSCP 46 (EF). I believe the
dscp-mutation map assumes dscp is trusted. If you wanted to convert
incoming DSCP 40 to outgoing DSCP 46 (EF) you might use this map. Not sure
if this relates directly to your question, but hope it helps.
Bob Sinclair
CCIE #10427, CISSP, MCSE
www.netmasterclass.net
----- Original Message -----
From: "Edwards, Andrew M" <andrew.m.edwards@boeing.com>
To: <ccielab@groupstudy.com>
Sent: Tuesday, October 26, 2004 8:15 PM
Subject: Re: 3550 qos dscp mutation map question
>I haven't been able to drum up a clear answer in my mind on this one...
>
> If I set a port to trust cos, I know that the default COS (or 0) is
> applied to unmarked traffic. What I don't know is if the switchport
> marks the IP packet with the DSCP value to the cos-to-dscp map?
>
> Or, is the DSCP mapping just another way the switch could filter/act on
> the packet?
>
> Any help with this is appreciated.
>
> andy
>
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