RE: WG last call: draft-ietf-tewg-diff-te-reqts-04.txt

["Sudhakar Ganti" <sganti@tropicnetworks.com>]

Hello,

It is not clear to me what the specification of
bandwidth constraint (BC) model brings to DS-TE solution
as described in this draft. Current solution assumes
that each LSP belongs to a TE-Class and the constraint
based routing uses available bandwidth for TE-Class
that is advertised in computing a path. That is all
what is needed. BC information has local significance
in computing the TE-Class available bandwidth, but need
not be propagated to other nodes.

Depending upon the network design and traffic matrix,
different bandwidth sharing models may be deployed
in a network. Do we want to enforce the same model
on every link across the whole domain ? What if the 
models are different? Do we want to reject the path setup? 
Besides, the LSP setup is based on the advertised available 
bandwidth of TE-Class. Is it not sufficent that whatever 
is the bandwidth model, as long as one computes correct 
available bandwidth for TE-Class and advertises, we can
setup paths correctly? How would one use the knowledge
of BC model for this purpose when constraint based
routing is purely based on available bandwidth per TE-Class?

Different BC models may have different implications of
call blocking etc in various scenarios. But that should
be left to network design and we should not be specifying
what a default model should be. Is there any interoperability 
issue in the network if different models are used? Actually 
I don't even see the need to advertise this as being specified 
as optional IGP TLV in the DS-TE protocol draft.
 
Therefore, a discussion on BC models in the draft 
(e.g., various models and their performance) is fine. But
I don't see a need for "mandating" or specifying what
the default model should be and the corresponding unnecessary 
protocol extensions.

Any comments??

Regards
-Sudhakar

> -----Original Message-----
> From: Jim Boyle [mailto:jboyle@pdnets.com]
> Sent: Sunday, May 19, 2002 10:04 PM
> To: te-wg@ops.ietf.org
> Subject: WG last call: draft-ietf-tewg-diff-te-reqts-04.txt
> 
> 
> 
> This message begins a WG last call for the following:
> 
> 	draft-ietf-tewg-diff-te-reqts-04.txt
> 
> This WG document addresses a WG milestone.  It is proposed as an
> Informational RFC.  WG last call ends May 31, 2002.
> 
> 
> 
> 
>