[j-nsp] Use cases for IntServ in MPLS backbones

[Saku Ytti]

On Tue, 2 Oct 2018 at 14:22, Alexandre Snarskii <snar at snar.spb.ru> wrote:

> marking to [mis]classify packet. Of course, you can use ultimate-hop
> popping (explicit-null) so MPLS EXP can be used at egress router too,
> but in this case egress router will not decrement ip ttl and generate
> icmp unreachable/ttl exceeded and so will not be shown in traceroutes
> making troubleshooting much harder.

You indeed must run explicit null if you have full pipe model or
really want to do any QoS based on MPLS overlay.

However the TTL decrement issue isn't inherent, there are platforms
where hardware can't do it. And obviously you can't buy that hardware
if you intend to do QoS on overlay, so then you're definitely network
which does QoS underlay and must reset.

Trio handles EXP null and decrement just fine, I think PFC3B catalyst
did not but PFC3C catalyst did. Unsure about ICHIP and IP2.

-- 
  ++ytti