igor - see in-line
beside this i welcome the serious re-writing effort provided by the authors compared to the previous version of this document
"Igor Bryskin" <ibryskin@movaz.com>
Sent by: owner-ccamp@ops.ietf.org
07/17/2005 13:18 AST
To: <i-d-announce@ietf.org>, <Internet-Drafts@ietf.org>
cc: <ccamp@ops.ietf.org>
bcc:
Subject: Re: I-D ACTION:draft-ietf-ccamp-lsp-stitching-01.txt
Arthi && JP.
I have a couple of questions.
1. Why are saying that LSP Stitching is a private case of LSP Hierarchy?
[dp] purpose is imho on the control plane mechanism and from this perspective only point 4) remains - the effect of having a "logical" TE link -
IMO there is more differences than similarities:
The differences are:
1) In case of H-LSP there is a data plane adjacency, while in case of S-LSP
there is none (as you correctly pointed out);
2) In case of H-LSP there is an adaptation in data plane (label push/pop for
PSC), while in case of S-LSP there is none - just simple cross-connecting
( label swap) as in case of two "native " e2e LSP adjacent segments ;
3) H-LSP could be used by many e2e LSPs, while S-LSP could be used by
exactly one e2e LSP
4) Signaling is different - there is no label negotiation in stitching
5) H-LSP is used as a "true" data link, specifically there is a resource
allocation on the H-LSP edges, while in case of S-LSP there is none
6) From MLN point of view, H-LSP is created in a server (lower) layer, while
the S-LSP is created in the client (same as e2e LSP) layer.
There are two similarities that I can think of:
1) There is a signaling and possibly routing (see below) adjacencies between
the ends;
2) Both H-LSP and S-LSP could be advertised as separate TE links or as TE
bundles
I would recommend to dedicate a paragraph and enlist there similarities and
differencies
[dp] i would simply recommend to state what an LSP segment is (as stated, this comparison has been used to show differences in terms of control plane processing and keeping it at that level is sensible) and not embark this document into terms and complex comparisons that are at the end of no real help
2. Why are you saying that a TE Link based on S-LSP can be used for exactly
one e2e LSP? Parallel S-LSPs could be advertised as a single TE link
(bundle, see above) and hence can accomadate several e2e LSPs.
[dp] i think the purpose is to say that a "triggered" LSP segment can be used by a single end-to-end LSP compared to the situation occurring with FA, where the triggered FA-LSP can then carry multiple nested LSPs
3. You are saying that S-LSP does not have a routing peering. Actually, in
this respect it is no different from H-LSP: if it is advertised as a TE link
into the same TE domain that was used for S-LSP creation (unlikely IMO
scenario) than it does not require the routing adjacency (in other words, it
is an FA according to LSP-HIER definition), otherwise, it IS NOT and FA and
does require the direct routing peering in the domain it is advertised to
make it useful as a TE link in this domain
[dp] again the document correctly states that a routing adj. is not going to be established on the LSP segment
Cheers,
Igor
----- Original Message -----
From: <Internet-Drafts@ietf.org>
To: <i-d-announce@ietf.org>
Cc: <ccamp@ops.ietf.org>
Sent: Friday, July 15, 2005 3:50 PM
Subject: I-D ACTION:draft-ietf-ccamp-lsp-stitching-01.txt
> A New Internet-Draft is available from the on-line Internet-Drafts
directories.
> This draft is a work item of the Common Control and Measurement Plane
Working Group of the IETF.
>
> Title : Label Switched Path Stitching with Generalized MPLS Traffic
Engineering
> Author(s) : A. Ayyangar, J. Vasseur
> Filename : draft-ietf-ccamp-lsp-stitching-01.txt
> Pages : 19
> Date : 2005-7-15
>
> In certain scenarios, there may be a need to combine together two
> different Generalized Multi-Protocol Label Switching (GMPLS) Label
> Switched Paths (LSPs) such that in the data plane, a single end-to-
> end (e2e) LSP is achieved and all traffic from one LSP is switched
> onto the other LSP. We will refer to this as "LSP stitching". This
> document covers cases where: a) the node performing the stitching
> does not require configuration of every LSP pair to be stitched
> together b) the node performing the stitching is not the egress of
> any of the LSPs c) LSP stitching not only results in an end-to-end
> LSP in the data plane, but there is also a corresponding end-to-end
> LSP (RSVP session) in the control plane. It might be possible to
> configure a GMPLS node to switch the traffic from an LSP for which it
> is the egress, to another LSP for which it is the ingress, without
> requiring any signaling or routing extensions whatsoever, completely
> transparent to other nodes. This will also result in LSP stitching
> in the data plane. However, this document does not cover this
> scenario of LSP stitching.
>
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