The MPLS WG Archive

[Vishal M <vishal_study@yahoo.com>]

Sami and Nabil,

My understanding of implementing DiffServ with MPLS
RSVP TE is:

1. With E-LSPs, we can signal upto 8 PSCs; all mapping
to a single LSP.

2. During LSP establishment:
2a. SENDER_TSPEC object specifies the bandwidth
requirement for the LSP (i.e. commulative bandwidth
requirement for all 8 PSCs). This SENDER_TSPEC remains
the same as for traditional RSVP or MPLS RSVP TE.

2b. CLASSTYPE Object specifies the bandwidth pool to
be used for performing CAC etc for that LSP. This
object is defined in the "Protocol extensions for
support of  
Diff-Serv-awae MPLS Traffic Engineering";
draft-lefaucheur-diff-te-proto-00.txt.

2c. DIFFSERV Object specifies the EXP<=>PHBID mapping
for that particular LSP. This object is defined in 
"MPLS Support of Diff-Serv", draft-ietf-mpls-diff-ext-
09.txt). There are issues in signalling these mapping
for each LSP (currently being discussed in a different
thread).

With the above mentioned drafts/specs, there is no way
to signal bandwidth requirement for each PSC carried
in the LSP. 
The draft draft-ganti-mpls-diffserv-elsp-00.txt
addresses this issue.

Questions:
==========
Nabil, you mentioned that CLASSTYPE object is not used
when signalling E-LSPs and is only used for L-LSPs. I
don't understand this one...could you please
elaborate? 

1. Why is it useless to specify CLASSTYPE with E-LSPs
?
2. What does CLASSTYPE signify for L-LSPs ?

Thanks again for your time,

Regards,
Vishal.

--- Nabil Seddigh <nseddigh@tropicnetworks.com> wrote:
> Sami,
> 
> I think we may be saying roughly the same thing.
> 
> The point I wanted to stress is that CLASSTYPE alone
> is useless if
> you are using E-LSPs. I think this point is
> recognized by a number
> of folks. As the WG drafts exist today, this object
> can only 
> be used with L-LSPs. i.e. where you only need signal
> one set of
> traffic parameters per LSP.
> 
> 
> Nabil
> 
> 
> 
> > 
> > Nabil:
> > The problem you are describing is a generic
> problem
> > with E-LSPs, not specific to CLASSTYPE (or
> DiffServ TE).
> > When an E-LSP is signalled, the signalled
> bandwidth
> > is associated collectively to the whole LSP, not
> > individual PSCs. Therefore, it is not possible
> > to do diffserv resource adjustments (e.g., queue
> bandwidth)
> > based on the signalled bandwidth.
> > The draft you are pointing out is a good first
> attempt
> > to solve some of these issues. However, IMHO,
> E-LSPs and
> > DiffServ TE concepts still require a lot of work.
> > 
> > Regards,
> > --Sami
> > 
> > > -----Original Message-----
> > > From: Nabil Seddigh
> [mailto:nseddigh@tropicnetworks.com]
> > > Sent: Wednesday, November 07, 2001 11:29 AM
> > > To: Iren, Sami
> > > Cc: 'Vishal M'; mpls@UU.NET
> > > Subject: Re: CLASSTYPE object
> > >
> > >
> > > Sami,
> > >
> > > Currently, the CLASSTYPE object cannot really be
> used with
> > > E-LSPs in the manner you describe. The CLASSTYPE
> object is only
> > > useful with L-LSPs.
> > >
> > > In order to utilize the concept of bandwidth
> pools in E-LSP,
> > > one needs to be able to signal traffic
> parameters per class
> > > or per-PSC. That capability is not present in
> the standards today.
> > >
> > > The closest proposal to achieve what you
> describe is the following:
> > >
>
http://www.ietf.org/internet-drafts/draft-ganti-mpls-diffserv-
> > elsp-00.txt
> > 
> > Best,
> > Nabil Seddigh
> > 
> > >
> > > Your understanding that the CLASSTYPE is used to
> > > specify the bandwidth pool to be used for
> allocating
> > > resources during LSP Setup is correct. In this
> context,
> > > the service class which is signalled via EXP
> bits
> > > (in the case of E-LSPs) dictate the treatment
> given
> > > to the individual packets, and the CLASSTYPE,
> which
> > > is signalled per LSP, dictates where the
> bandwidth
> > > is coming from (used in CAC).
> > >
> > > [....deleted....]
> > >
> > > Ideally, I would prefer to get rid of the
> CLASSTYPE
> > > concept and advertise available bandwidth per
> service class.


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