RE: TE Requirements Draft - ELSP

[Francois Le Faucheur <flefauch@cisco.com>]

Hi,

At 12:51 22/11/2001 +0000, neil.2.harrison@bt.com wrote:
> >
> > Is it correct that what you are describing here is the
> > ability to transport
> > multiple OAs on a single LSP and have the path for this LSP
> > be computed
> > based on one "effective Bw" for that LSP , and have one single
> > survivability policy/attribute (as opposed to one independent
> > survivability
> > policy/attribute for each OA)?
>NH=> Effectively yes.  As I tried to point out previously, there is no
>relationship between an applications up-state QoS requirements (ie in DS
><clip>

In the hope of progressing towards some agreement, here's an updated 
analysis of the thread + corresponding proposal:

There are (at least) three "ways" E-LSPs may potentially be used for DS-TE :

1) using E-LSPs with traffic from a single OA:
==============================================
This option is already explicitely allowed in the recently posted REQTS draft.
I suggest that this stays so, since everybody's happy with that.

2) using E-LSPs with traffic from multiple OAs but using single CSPF
=====================================================================
This option is not allowed in recently posted REQTS draft.
This option is necessary to:
         - address Jim's scenario
         - address Roberto's scenario
         - address Neil's scenario
This option would not create any real changes to the current DS-TE model 
and entails NO protocol extensions (ie it comes for free complexity-wise)
I suggest that the REQTS draft be changed to allow this option.

3) using E-LSPs with traffic from multiple OAs each with their own SPF
======================================================================
This is not allowed in recently posted REQTS draft.
As Nabil/Sudhakar indicated, it is conceivable that some Service Providers 
might want to do that one day.
But this require departure from the current DS-TE model and entails 
protocol extensions.
I suggest we keep this option on the table for discussion for now but don't 
include it in the REQTS draft until we have established that a body of SPs 
actually want to do this and how it would actually be used (would we need 
just multiple bandwidth or also multiple affinity, multiple preemption,...).
This would allow us to develop a faster simpler DSTE solution that 
addresses what we know SPs want to do today.
We can always add this option at any time later when deemed useful and do 
the corresponding work then.

Looking forward to hearing thoughts on this analysis/suggestion.

Francois

_________________________________________________________
Francois Le Faucheur
Development Engineer, IOS Layer 3 Services
Cisco Systems
Office Phone:          +33 4 97 23 26 19
Mobile :               +33 6 89 108 159
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Email:                 flefauch@cisco.com
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