[c-nsp] 7600s, DSCP, ASICs, Bollocks

[James Bensley]

On 13 October 2015 at 16:47, Anon wrote:
> It shouldn't be necessary in your situation, but I'm curious if adding
> "platform ip features sequential" on the ingress interfaces where
> marking is occurring would help. This should only be necessary if you
> are marking on ingress and then taking action on the new marking in
> the same box. It should have zero bearing on if the packet is actually
> re-marked on egress, but it might be worth a shot for troubleshooting
> purposes.

Interesting, I didn't know that command so I'm reading about it now.

TAC have asked if I can add a policy with "set mpls experimental
imposition 0", I guess there logic is something like:

Traffic comes in via transit provider attached to 7600-PE1, label is
pushed, label switched over to 7600-PE2. PE1 has pushed the label
before setting DSCP so the DSCP isn't being removed (maybe the DSCP
removal actually happens on egrees of the incomming line card into the
crossbar or something like that, not as soon as the packet comes into
the port ASIC, but since this packet gets a label pushed maybe that
also happens before the packet egresses the line card into the
crossbar so the DSCP isn't removed when the packet leaves the line
card becasue it's now a labelled packet).

However they haven't explained why I should do this, so I've thrown it
back at them to explain.


Cheers,
James.