[j-nsp] CoS Marking/Rewrite Theory

[Pekka Savola]

On Sun, 5 Oct 2008, Chris Evans wrote:
> Yea I don't want to assign them to seperate queues, but I do not want
> packets that already have a DSCP bit assigned to be rewritten. If I have
> more differentiated traffic then classes available on the box, I'm out of
> luck essentially. Also I'm not using the M320 or T series.. I'm really
> working with the other M series, MX switches and EX series switches.

FWIW,

"I do not want packets that already have a DSCP bit assigned to be 
rewritten" appears to be a sentiment that Juniper isn't very committed 
to. In earlier M-series, you could rewrite DSCP's on some forwarding 
classes only.  On T-series and M320, if you haven't configured a 
rewrite rule on all the forwarding classes, the router ends up 
clearing DSCPs for the other forwarding classes, with no possibility 
to preserve the DSCP.

http://www.juniper.net/techpubs/software/junos/junos92/swconfig-cos/assigning-the-rewrite-rules-configuration-to-the-output-logicalinterface.html

Pretty annoying.  Too bad these kinds of issues seem to crop up more 
and more, usually after you've already bought the box or a new kind of 
interface :-/

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings