Subject: RE: [mpls] mpls wg review of draft-ietf-avt-hc-mpls-reqs-03.txt

From: "Ash, Gerald R \(Jerry\), ALABS" <[email-masked]>
Date: Fri, 24 Sep 2004 12:01:36 -0500

Thomas,

Thanks for the comments.

> Some comments on the draft "draft-ietf-avt-hc-mpls-reqs-03.txt" below:
> 
> "Figure 1 illustrates an HC over MPLS session established on an LSP
that 
> crosses several routers, from R1/HC --> R2 --> R3 --> R4/HD, where
R1/HC is 
> the ingress router where HC is performed, and R4/HD is the egress
router 
> where header decompression (HD) is done. HC of the RTP/UDP/IP header
is 
> performed at R1/HC, and the compressed packets are routed using MPLS
labels 
> from R1/HC to R2, to R3, and finally to R4/HD, without further 
> decompression/recompression cycles."
> 
> The text and also the figure seems to indicate LSPs all the way to
router 
> R4. Would this work with penultimate hop popping?

I see no reason this wouldn't work with PHP.  The egress router does not
necessarily expect a label.

> Do you intend to identify the compressed packet by incoming interface
and 
> SCID? This would work, but matching of SCID at the incoming interface
would 
> demand some extra implementation.

The incoming compressed packet is identified only by the SCID, not the
incoming interface or label.  The proposed mechanism for obtaining
SCIDs, as discussed in the protocol extensions draft
http://ietf.org/internet-drafts/draft-ash-avt-ecrtp-over-mpls-protocol-0
1.txt, would ensure unique SCIDs at the egress router.

> When thinking about it some more, could it be a problem with multiple
LSPs 
> terminating at the same incoming interface and compression is used
over 
> them because of colliding SCIDs? Again with PHP.

Yes, it would be a problem.  That's why the protocol extensions draft
proposes a method to ensure unique SCIDs at the egress router.

> Regarding "Extensions to MPLS signaling", I assume that this signaling
is 
> not intended to be done along with the actual LSP setup but rather
between 
> "HC-ingress" and "HD-egress"?

Right.

> Thanks,
> Thomas

Thanks,
Jerry

> -----Original Message-----
> From: [email-masked] 
> [mailto:[email-masked]] On Behalf Of Loa Andersson
> Sent: Tuesday, September 21, 2004 9:08 AM
> To: [email-masked]
> Subject: [mpls] mpls wg review of draft-ietf-avt-hc-mpls-reqs-03.txt
> 
> All,
> 
> the avt working group has requested that
> draft-ietf-avt-hc-mpls-reqs-03.txt should be
> published as an Informational RFC.
> 
> Our AD's asks that we (the mpls working group) review
> and comment on the draft.
> 
> Since it is my ambition to send our response on Monday
> please send any comment to me before that.
> 
> /Loa
> 
> -- 
> Loa Andersson
> 
> Principal Networking Architect
> Acreo AB                           phone:  +46 8 632 77 14
> Isafjordsgatan 22                  mobile: +46 739 81 21 64
> Kista, Sweden                      email:  [email-masked]

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