Hi Dan,
On Jul 7, 2007, at 6:29 AM, Dan Li wrote:
Dear the authors of BRPC,
We just published a new draft which we think is worth to be
reviewed by you:
http://tools.ietf.org/wg/pce/draft-xia-pce-hybrid-network-00.txt
The purpose of the draft is:
- This draft is primarily to explain a problem that we think is a
real deployment scenario;
- We believe that BRPC can be used to solve the problem;
- If the WG is in agreement, we would like to propose a few
paragraphs to be added to [brpc];
- If the WG would like to discuss this issue more, we would be
happy to present it in Chicago.
Please let us know what's your suggestion. We greatly appreciate
your time to look at this new draft.
As you know the whole point of using a Multi-PCE approach with BRPC
is to compute
the shortest inter-domain constrained path (in addition to diverse
paths, ... ).
The case you're looking at in this ID (called Hybrid network) can no
longer guarantee that
you'll find the shortest path of course.
Referring to your first example, the most downstream PCE will only
see the next hops
to the downstream domain. So even if by using BRPC between the first
set of domains
where you have cooperative PCEs you get the shortest path between the
source and
the set of entry boundary nodes of the first non-PCE domain, this
does not guarantee
you anything in term of path efficiency ...
Furthermore since you get several paths, would you try to signal two
TE LSPs in which
case they may end up blocking each other ?
Note that this comment applies to the first two cases of section 2.2
The case 3 of section 2.2 suggests to use Virtual Inter-AS TE Links:
please refer to the
discussions on the list with regards to TE aggregation: this option
has been examined
a number of times and has been rejected. Adrian and I still have in
our plate to document this.
And of course, if you start to alternate a number of PCE enabled and
non PCE enabled
domains, the result gets not only extremely complex but more
importantly highly unpredictable
in term of path quality.
Thanks.
JP.
Best regards,
Dan Li & Hongmiao Xia
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