RE: [Pce] A New Internet-Draft on Advertising of inter-AS TE links

["Greg Mirsky" <[e-mail]>]

Dear Zhang,
thank you for your response. I've read the newer version of the draft as
you suggested and below are my questions:
- would you agree that usually ASBRs are eBGP speakers and are fully
mesh connected. In that case eBGP can be viable solution for the
inter-AS TE links computation by ASBR.
- I'm concerned with scaling aspect of flooding inter-AS TE information
throughout both AS and an area and I see that you're concerned as well
(SHOULD for Type 10 and MAY for Type 11). I think that it would be
helpful if use of both Type 10 and Type 11 for inter-AS TE Link
advertisement be illustrated by scenarios. I think that use of area
scope makes these OSPF extensions less applicable to inter-AS path
computation by the head-end LSR/LER.
- Could you please illustrate which links are excluded by the following:
"   Routers or PCEs that are capable of processing advertisements of 
   inter-AS TE links SHOULD NOT use such links to compute paths that 
   exit an AS to a remote ASBR and then immediately re-enter the AS. 
   Such paths would constitute extremely rare occurrences and MUST only 
   be allowed as the result of specific policy configuration at the 
   router or PCE computing the path."
Are there two links that interconnect a pair of ASBRs that belong to two
different neighboring ASes?

	Regards,
		Greg

-----Original Message-----
From: Zhang Renhai [mailto:[e-mail]] 
Sent: Thursday, February 01, 2007 6:36 PM
To: Greg Mirsky; [e-mail]; [e-mail]
Subject: Re: [Pce] A New Internet-Draft on Advertising of inter-AS TE
links

Hi, Greg

Thanks a lot for your question.
See inline please.

Dear Zhang,
I have couple questions related to Link ID of inter-AS link. According
to the document it is the Router ID of Remote ASBR. 
[ZRH]Yes, and this can be easily got by manual configuration in the
local ASBR.

My question:
- as I understand the mechanism of how TE information for links R6-R9
and R8-R10 is populated into R5's TE DB is outside the scope of this
document. I this mechanism is not IGP but EGP (BGP), then what is the
benefit to introduce new LSA in IGP (OSPF) and not use exisitng
mechanisms.

[ZRH]I think BGP could also be another alternative especially for PCE
scenario, but it's not very applicable to per-domian method because the
inter-AS TE information may be needed throughout the local AS in case
that the path computation function is distributed among LSRs in the
local AS, and BGP can hardly advertise the TE information among those
LSRs if BGP sessions are not established between the ASBR and those
LSRs. So IGP extension is considered in this draft.

We have submitted the revised version of this draft, hoping make the
problem statement more clear, and relax the use of type 11 opaque lsa,
also allow Type 10 lsa (by which the advertising scope is an area of
OSPF).
http://www.ietf.org/internet-drafts/draft-chen-ccamp-ospf-interas-te-ext
ension-01.txt

Cheers,
Zhang Renhai


Regards,
Greg

PS. I think that OSPF WG needs to be informed as well.

-----Original Message-----
From: Zhang Renhai [mailto:[e-mail]]
Sent: Tuesday, January 30, 2007 7:38 PM
To: [e-mail]; [e-mail]
Subject: [Pce] A New Internet-Draft on Advertising of inter-AS TE links


Hi, allWe have just submitted the following draft in which we describe
some problemsin inter-AS TE scenarios and the corresponding OSPF
extension is introduced.PCE environment is also considerd in this I-d so
I'd also like pce working groupto pay attention to it.we'd highly
appreciate your comments.Thanks a lot,Zhang Renhai & Mach A New
Internet-Draft is available from the on-line Internet-Drafts 
directories.


Title : OSPF Extensions in Support of Inter-AS (G)MPLS TE 
Author(s) : M. Chen, R. Zhang
Filename : draft-chen-ccamp-ospf-interas-te-extension-00.txt
Pages : 9
Date : 2007-1-30

   This document describes extensions to the OSPF to support inter-AS 
   Traffic engineering (TE). It defines OSPF extensions for the flooding

   of inter-AS links information which can be used to perform inter-AS 
   path computation. 


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