[c-nsp] Short pipe with Inter-as option 10b

[Oliver Boehmer (oboehmer)]

Vikas Sharma <mailto:vikassharmas at gmail.com> wrote on Friday, June 06,
2008 5:11 AM:

> Hi,
> 
> Need your expert comment on what QoS mechanism to be used for
> Inter-As option 10b, pipe mode or short pipe mode. This is for ISP
> setup. What is the trend in ISP industry?  

well, Inter-Provider QoS is still a general challenge (whether it is
MPLS-VPN InterAS or plain IP interconnectivity). 
My personal take on this (possibly not having a conclusive picture of
what's being done):

- On the ASBR in a 10b setup, packets are rcvd and sent labelled, so
pipe vs. short-pipe doesn't apply (the difference between pipe and
short-pipe is the QoS classification on the IPv4 PE-CE link at the very
edge of the network).

- If 10b is used and the QoS classes don't match, you re-classify by
changing EXP bits of the top label, so the ASBR plays the same role as a
P node, and changing MPLS PHB on P devices is possible with any MPLS
Diffserv tunneling modes, including uniform mode, so the question pipe
vs. short-pipe doesn't apply.

- Many providers actually prefer Inter-AS option 10a as they can look at
the IPv4 header to apply granular filtering and QoS. Obviously, 10a has
scalability challenges, and a new Inter-AS option 10d (or 10a+b)
draft-kulmala-l3vpn-interas-option-d addresses those by combining the
IPv4 forwarding properties of 10a with the scalable vpnv4 control plane
of 10b, so I might also call this a "trend".

my 2c

	oli