RE: Alternative to draft-ash-mpls-diffserv-te-class-types-00.txt ?

["Ash, Gerald R (Jerry), ALCTA" <gash@att.com>]

Sanjay,

Some comments below.

Thanks,
Jerry Ash

> b. From the recent posting, I sense that the
> new revision of DS-TE-REQTS will remove the 
> Class-Type as a requirement.

Not so, CT remains in the upcoming DS-TE-REQTS draft.

> The DS-TE scalability issue can be handled by the some
> of the existing DS-TE proposals (kompella,ash,boyel..)

This is a different scalability issue than addressed in the current draft.
E.g.,
http://search.ietf.org/internet-drafts/draft-ash-mpls-diffserv-te-alternativ
e-02.txt and
http://search.ietf.org/internet-drafts/draft-ash-ospf-isis-congestion-contro
l-01.txt address concerns about scalability of IGPs and extensions of LSAs
to communicate per-CT available bandwidth, etc. In particular, the former
('te-alternative') draft proposes 'no further IGP extensions' to support
CTs, and illustrates one possible technical solution which avoids further
extensions to the IGP.  Some progress is being made now toward that 'no
further extensions' objective.

The scalability issue discussed in the current draft
http://search.ietf.org/internet-drafts/draft-ash-mpls-diffserv-te-class-type
s-00.txt (e.g., see Section 3) is to reduce the dimensionality/complexity of
possible CTs across 4 levels of priority (DiffServ PHBs, admission-control
priority, restoration priority, preemption priority).  The intent is to
reduce a possibly very large number of independent CTs to 6, by combining
the 4 priority-dimensions into a smaller number (6) of CT combinations.  We
feel that this approach is more scalable than allowing a very large number
of CT combinations.

Another motivation for defining consistent CTs (also pointed out by Wai Sum)
is for consistent mapping of services across SP network boundaries to
achieve end-to-end QoS.  This objective is not new, but has already been
addressed in other standards fora for similar reasons (see the references in
the I-D for more information).  Services such as emergency services, for
example, (as discussed in
http://search.ietf.org/internet-drafts/draft-folts-ieps-white-paper-00.txt,
http://search.ietf.org/internet-drafts/draft-baker-ieps-requirements-00.txt,
and http://search.ietf.org/internet-drafts/draft-schulzrinne-sip-911-01.txt)
need to cross multiple SP networks with consistency and interoperability on
priority treatment, etc.