The MPLS WG Archive

[Heiles Juergen <Juergen.Heiles@icn.siemens.de>]

John,

I agree that at the endpoints of a trail (in ITU terms), where the signal that is connected through the network is terminated, the same processing for the payload is needed (either multiplexing or any other kind of adaptation). However this is not part of the LSP and of the LSR functionality. Consider a Optical Channel/lambda LSP. According to the document - as I read it -  the LSP is should be terminated on a LSR with Lambda switch capable (LSC) interfaces (e.g. an optical switch), hwoever the paylaod of the Optical Channel is a SDH or IP signal which require TDM or packet processing.
For sure you want to connect your signal between endpoints with the same client processing, but this is only of interest for the selection of the correct endpoints, but not for the LSP set-up itself. The LSP set up should only care about the signal itself and not about its payload. FAX and telphones use the same infrastrucutre for the setup of the connection, you have to be shure to connect the same endpoints by using up to correct number or you have a automatic selection of the correct payload processing using signaling. This signaling should only apply to theendpoints and not to intermediate  nodes.

Furthermore a LSP -at least for circuit switching - doesn't have to start and end at the trail termination where you extract your payload. A LSP could be used only for a sub part of the overall connection, e.g. a DS1 signal starts in a user domain with tradional TMN path setup or even manual connections, the DS1 comes to a operator which uses GMPLS for path -setup (in this case a permanent connection set-up by himself as the user doesn't support the UNI). The LSP starts in the middleof the overall DS1 connection and no access to the paylaod of the DS1 is requried at that point.

	Regards

	Juergen


> -----Original Message-----
> From:	John Drake [SMTP:jdrake@calient.net]
> Sent:	Wednesday, December 06, 2000 5:14 PM
> To:	'Heiles Juergen'; mpls@UU.NET
> Cc:	ip-optical@lists.bell-labs.com
> Subject:	RE: [IP-Optical] GMPLS - Hierarchies
> 
> 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
> 
> 
> 
> 
> 
> 
> 
> _______________________________________________
> IP-Optical mailing list
> IP-Optical@lists.bell-labs.com
> http://lists.bell-labs.com/mailman/listinfo/ip-optical