The MPLS WG Archive

[John Drake <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.
Take for example an optical cross-connect that switches fiber between its
ports (=> fiber switch capable). The single or multiple lambdas on this
fiber might be directly after the cross-connect or later combined with other
signals from other fibers in a WDM system => (lambda switch capable) or a
TDM technique is used to combine several of these signals to a higher
bandwidth signal (e.g. going from 2.5 to 10 Gbit/s) (=> time switch
capable). So a LSP that starts at LSC device ends up at a TSC device and
might have a LSC device in between. Even an interchange of LSPs between
packet and circuit switch capable devices is possible, take for a example
circuit emulation via ATM. With circuit emulation you can also have a LSP
that starts on a TSC device nested into a LSP that starts on a PSC device.
A LSP represents a connection through the network/sub-network for a certain
signal. This is independent of the switching technologies along the route
and at the end as long as the specific signal is supported. At both ends
access to the specific signal has to be provided, but it doesn't matter if
e.g. a 1.5 Mbit/s signal is transported on a time-slot of a TDM system, on a
single wavelength of a WDM system (not economic), over a CDMA radio system
or with circuit emulation over an ATM network.
The Hierarchy is defined by different signals nested into each other
(client/server relationship), but not by the switching types.

Regards

Juergen Heiles







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