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

[James Bensley]

On 17 November 2015 at 17:46, Sigurbjörn Birkir Lárusson
<sigurbjornl at vodafone.is> wrote:
> This email sums up the 7600 very well, particularly the last word in the subject :D
>
> Kind regards,
> Sibbi

> On 17/11/15 17:41, "cisco-nsp on behalf of James Bensley" <cisco-nsp-bounces at puck.nether.net on behalf of jwbensley at gmail.com> wrote:
>>Switching to uniform mode work, using the global config command "mls
>>mpls qos input uniform-mode".
>>
>>Now PE1 will set DSCP 0 on the incoming transit packets however, even
>>in short pipe mode, if the port is untrusted I would have expected the
>>DSCP to be set to 0. It seems in short pipe mode no actions can be
>>made against the DSCP/ToS value at ingress only egress.

TAC have confirmed this is more or less a bug with the platform and
there is an internal bag case CSCuw80912 which the developers have
looked at. There is no intention to fix this though as it seems to be
some sort of limitation of the way the PFC hardware works.

It seems "mls mpls qos input uniform-mode" toggles uniform mode and
also performs some additional steps internally so that the PFC can set
re-write DSCP on ingress, to work around the issue.

Cheers,
James.