[j-nsp] CoS Marking/Rewrite Theory

[Mark Tinka]

On Saturday 04 October 2008 10:45:28 Chris Evans wrote:

> I come from a Cisco world and am learning JUNOS. I have a
> question in regards to CoS markings on packets. In Cisco
> devices I can modify Layer2 or Layer3 CoS header
> information INGRESS an interface. From my reading in
> Juniper Devices you can only write that information
> EGRESS an interface and it comes from the 'rewrite-map'.

This is something we discovered while PoC'ing the MX-series 
(we hadn't been running QoS on our existing Juniper kit to 
discover it then, but are now). Remarking is generally done 
outbound.

There are cases where remarking inbound might be easier to 
do, for instance, if only one or two traffic flows need to 
be affected, e.t.c.

We discussed this with our Juniper SE several months ago and 
they said there are plans to support ingress remarking on 
the MX-series. Not sure if, when this became available, 
said feature would be available on other M-series platforms 
as well... perhaps it's time to re-engage this issue.

Suffice it to say that the M320 and T-series boxes do 
support the remarking of inbound traffic to 'DSCP 0' 
through the use of a firewall filter. This has become 
available since JunOS 9.0, IIRC, and supports both IPv4 and 
IPv6.

Cheers,

Mark.
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