The MPLS WG Archive

[neil.2.harrison@bt.com]

Spot on John.  Its called layering in functional architecture.  Each LSP
creates a layer network.  It has a source and a sink point at which certain
characteristic information (eg the shim header for MPLS, or some other
header if say ATM-based MPLS is being used (actually also the AAL)) is
applied and removed respectively.  The header is only relevant between these
points and *should* have no direct impact on other client or server layers
during normal operation (things are different under failures...I must get
that OAM ID out!)......if it does there is danger of layer violation causing
both backward and future cross-layer evolutionary problems, re my various
mail concerns on EXP, TTL and PHP issues that some will have seen wrt to the
shim header and the point of LSP trail termination and server->client
(layer) adaptation.

I really believe if more people had a better understanding of this (ie func
arch) then we could make better and more accurate progress.  Many of the
questions I see coming up are because what are to me/others basic functional
arch concepts are not understood or being applied.  Can I make a plea to
those who have access to G.805 to go and have a look at it and those that
don't check out the Book from Andy Reid (a close colleague of mine) and Mike
Sexton [Broadband Networking, Hardcover - 589 pages 1st edition (January 15,
1997) Artech House; ISBN: 0890065780].  This work was found essential to
unambiguously define SONET/SDH......not by operators, but by manufacturers
......and is in common usage today in many parts of our industry.  It is
also applicable to all other layer network technologies I can think of.

Neil

> From:	John Drake [SMTP:jdrake@calient.net]
> 
> Jergen,
> 
> An LSP has an two endpoints.  At the ingress endpoint, a node is
> multiplexing stuff into a given LSP.  At the egress endpoint, a node is
> demultiplexing stuff from that LSP.  If the ingress and egress endpoints
> aren't multiplexing and demultiplexing stuff consistently, how is stuff
> able
> to successfully transit the LSP?
> 
> Thanks,
> 
> John 
> 
> -----Original Message-----
> From: Heiles Juergen [mailto:Juergen.Heiles@icn.siemens.de]
> Sent: Wednesday, December 06, 2000 4:34 AM
> To: mpls@UU.NET
> Cc: ip-optical@lists.bell-labs.com
> Subject: [IP-Optical] GMPLS - Hierarchies
> 
> 
> draft-ietf-mpls-generalized-signaling-01 mentions in the introduction a
> hierachy with fiber switching at the top followed by lambda, time-slot and
> packet switching and clearly distinguish between these levels. I don't
> agree
> with this view that a LSP starts and ends on the same LSR type and onyl
> nesting of LSPs of different LSR types is possible.
	<snipped>