[j-nsp] CoS Marking/Rewrite Theory

[Mark Tinka]

On Monday 06 October 2008 14:34:43 Pekka Savola wrote:

> 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/sw
>config-cos/assigning-the-rewrite-rules-configuration-to-th
>e-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 :-/

So I was following up with our SE on this earlier in the 
week, and he has raised an ER for this with the 
developers - but it's just that one, I think.

We'd need to get more requests in for it to become a 
consideration. If any of you have a sizeable deal going 
through with Juniper, and need this, this could move things 
forward quickly if it was a dependence.

In the interim, my SE had a discussion with their team and 
it is possible to remark the DSCP values for individual 
flows based on the inbound interface it came on - and the 
remark is universal for all outbound interfaces, whether 
upstream to the core or to other customers on the same 
router, as it's done in the PFE and not on the outbound 
interface.

Until the ER becomes a feature, we'll have to use this as we 
deploy more Juniper boxes where we've traditionally run 
Cisco.

Cheers,

Mark.
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