cos/dscp

From: Frank (ocsic@web.de)
Date: Wed Jul 11 2007 - 18:23:43 ART

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Hi,

i have a question regarding the cos/dscp mapping between switches that
are connected by trunks.

If i have the following setup

phone -trunk- switch1 -trunk- switch2 -

And the phone marke with cos5 for the voice traffic. I know the switch
needs an internal DSCP value for mapping to queues.

So the cos-to-dscp mapping maps cos5 to DSCP 46 for example. Then the
switch need to forware the frame over a trunk.

Does he need to convert the frame to a cos value again? Or is the frame
encapsulated with the new DSCP marking into an 802.1q trunk frame and on
the other side the switch can handle the frame with trust dscp on the trunk?

Or does the switch had to convert the frame from internal dscp to cos
again and then queue it regarding the cos value and then the other
switch receives it depending upon the cos to dscp mapping.

So are dscp to cos mappings also needed on the first switch?
I hope i made my question clear enough.

Frank

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