[j-nsp] MPLS and QoS at penultimate hop ?

[Christopher E. Brown]

The packet is classified on input.

*UNLESS* you use table-label in a l3vpn, then it gets re-classified
after the label POP.

On 2/3/13 6:03 PM, Chris Kawchuk wrote:
> It was my understanding that the label was "logically" popped on
> Egress (in terms of how one would envision the packet flow); hence
> the outer label EXP bits were evaluated by the BA classifier on
> ingress properly. (Whether it's popped on ingress, yet evaluated
> prior-to-pop is a mechanics thing..)
> 
> But yes, I have no documentation I can point to; off the top of my
> head that the above is indeed true. I would be interested to know for
> future information sake that the JNPR box is indeed "doing the right
> thing" so to speak… i.e. since the PIC/MPC pops the Layer-2
> information as well, it needs to be able to read the 802.1P bits, if
> there is a 1p-VLAN tag BA applied to the interface. Hopefully we're
> also reading the outer EXP label at the same time; as this would make
> sense.
> 
> i.e. if you're doing VLAN pop/swapping, you'd need to retain any
> BA-p-tag specific classification there as well, prior to any tag
> manipulation.
> 
> 400 quatloos says it's done on ingress before the label is popped.
> 
> - Ck.
> 
> 
>> 
>> Simple question I'm not able to find answer for: what is the order
>>  of label pop operation and BA classification on penultimate router
>> ?
>> 
>> I have a gut feeling that label is stripped first and then BA 
>> classification is done on a "naked" packet, f.e., ipprec-based in
>> case of IP packet, without taking (already stripped) EXP bits into
>>  account, but I can't find any documentation proving or disproving
>> it...
> 
> 
> _______________________________________________ juniper-nsp mailing
> list juniper-nsp at puck.nether.net 
> https://puck.nether.net/mailman/listinfo/juniper-nsp
> 


-- 
------------------------------------------------------------------------
Christopher E. Brown   <chris.brown at acsalaska.net>   desk (907) 550-8393
                                                     cell (907) 632-8492
IP Engineer - ACS
------------------------------------------------------------------------