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Re: Moving right along ...
Yanhe,
The situation Zhi describes is one that will be very typical in the optical
(SDH/SONET) network in the coming years. We will most likely see islands of
switched subnetworks interconnected via the existing SDH/SONET non-switched
networks. By means of management actions, links (GMPLS: link bundles) will be
setup between an edge node in one switched subnetwork and an other edge node in
the next switched subnetwork. In G.805 terminology, these links are so called
serial compound links.
The switched subnetworks will treat these serial compound links as normal links,
"ignoring" the intermediate non-switched nodes they traverse. These links will
contain a fixed set of link connections, which are identified by their
respective endpoints at nodes A and Z (i.e. SNPa - SNPz).
The server signal that carries the e.g. 5 STS1 link connections in the link at A
can be an OC12, whereas this can be an OC48 at Z.
During discovery or by means of provisioning both A and Z nodes get aware of the
5 sTS1 link connections as tuples of e.g.
SNPa SNPz
-----------------------------------
- port Ai/trib T1 - port Zj/trib Ta (STS1 link connection #1)
- port Ai/trib T2 - port Zj/trib Tb (STS1 link connection #2)
- port Ai/trib T3 - port Zj/trib Tc (STS1 link connection #3)
- port Ai/trib T4 - port Zj/trib Td (STS1 link connection #4)
- port Ai/trib T5 - port Zj/trib Te (STS1 link connection #5)
As both ends of the link build up this same relation information, it is possible
to use as link connection identifier only one of the two SNPs. E.g. node A
identifies the STS1 link connection #1 by means of "Ai/T1" and sends this info
to node Z. Node Z receiving this Ai/T1 converts this locally into "Zj/Ta". Vice
versa, node Z will refer to STS1 link connection #1 as "Zj/Ta" and when received
by node A, this will be converted into Ai/T1.
For GMPLS this implies that the GMPLS label doesn't identify the timeslot at
both ends of the link connection, only the timeslot at the sending end. The
receiving end needs to convert this then into its local timeslot number.
Regards,
Maarten
Yanhe Fan wrote:
>
> Hi Zhi,
>
> What B does is breaking the label association between A and C by crossing
> connect
> the time slots.
>
> If the cross connect performed by B is fixed (in your case), what needs to
> do is
> just to rebuild the label association by configuration or a protocol such as
> LMP;
> If the cross connect is not fixed but dynamic, the best thing to do is to
> make B
> a GMPLS speaker.
Tell this to the 1.000.000+ SDH/SONET network elements in today's transport
network... no chance... those will stay non-switched...
>
> Yanhe
>
> -----Original Message-----
> From: Zhi-Wei Lin [mailto:zwlin@lucent.com]
> Sent: Friday, October 19, 2001 6:01 PM
> To: Yanhe Fan
> Cc: John Drake; Kireeti Kompella; ccamp@ops.ietf.org
> Subject: Re: Moving right along ...
>
> Hi Yanhe,
>
> Maybe there is some misunderstanding. Node B is strictly not GMPLS. It
> is simply part of the network that made up the "dumb" pipe. And because
> the control plane control channel is separate, A and C can be adjacent
> without ever knowing who B is or that even B existed. From A and C's
> point of view, the network looks like:
>
> A ----- C
>
> Think of the case of how a BGP sees an area. If an area is made up of:
>
> A -- B -- C
>
> and B is internal router, does BGP "see" B?
>
> Zhi
>
> Yanhe Fan wrote:
>
> > Hi, Zhi
> >
> >
> >>For the label value for SONET/SDH or the label description in the
> >>generic draft, the label is defined as directly representing the
> >>"timeslot". Now if I have a control plane controlled transport network
> >>that goes through a ADM that is not control plane controlled, as:
> >>
> >>
> >>+--------+ +--------+ +--------+
> >>| | ---1--------- | | ----1-------- | |
> >>| | ---2--------- | | ----2-------- | |
> >>| A | ---3--------- | B | ----3-------- | C |
> >>| | ---4--------- | | ----4-------- | |
> >>| | ---5--------- | | ----5-------- | |
> >>+--------+ +--------+ +--------+
> >>
> >>Now imagine A and C is part of GMPLS, but B is just a legacy ADM. So at
> >>A you have labels 1,2,3,4,5 (imagine these as in the SUKLM format) and C
> >>has labels 1,2,3,4,5 incoming.
> >>
> >>Now imagine that at B, it actually has a fixed cross-connect that
> >>connects A-1 (A's timeslot #1) to C-2 (C's incoming timeslot #2), A-2 to
> >>C-3, A-3 to C-4, A-4 to C-5, A-5 to C-1.
> >>
> >>Now when A GMPLS sends a message to C, the label it uses is "1".
> >>However, the connection/LSP associated with timeslot "1" is actually the
> >>label of timeslot "2" at C. </z>
> >>
> >
> > In this case, you're trying to use GMPLS to setup an LSP cross a node (B)
> > which can't understand GMPLS.
> >
> > Now imagine A, B and C are all OXCs, can you setup an LSP A-B-C by using
> > GMPLS if B can't understand GMPLS?
> >
> > Now imagine A and B are LSRs, and B is a conventional router (can't
> > understand
> > MPLS), can you setup an LSP A-B-C?
> >
> > Now imagine A, B and C are ATM switches, can you setup a svc if B can't
> > understand PNNI at all?
> >
> > My point is that in order to make you case work, some additional work need
> > to
> > be done besie simply using GMPLS as singnaling protocol, becase some node
> on
> > the path is not GMPLS speakers. A and C needs the info of time slot
> aligment
> >
> > between them. This can be done by some configurations, some link
> management
> > protocls (LMP maybe) etc. As long as A and C have this piece of info,
> > eveything
> > works fine.
> >
> > Yanhe
> >
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