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Re: Sonet Ring provisioning
Let us say that the BLSR ring topology is as follows:
A --- B --- C
| |
H D
| |
G --- F --- E
If one wants to create a LSP from A to D via B, C, then A
signals to B, B to C, C to D. Everything is fine.
If B -- C link fails, what happens next?
1. Should B and C keep quite and do not tear down
LSP (because these know that B - C line is protected)?
How about H, G, F, E, D, C nodes?
Do these need to know that these are protecting an LSP that
goes through A to D? What happens if another link G - F fails?
Do these nodes need to inform B or C or A indicating that
these cannot protect B - C link anymore so that B can do
Fast Reroute?
2. Should B and C setup a backup LSP (when link fails) around the
ring? Traffic is not affected during this period. This provides
a mechanism for nodes involved in LSP can get information
from nodes that are in backup LSPs.
I think that there are quite a few issues are not resolved in
this area and taking a simple view is not going to be sufficient
when Fast Reroute and other things come into play.
Thanks,
Suresh
Zhi-Wei Lin wrote:
>
> Hi all,
>
> Seems we have mixed up a "ring topology" from "ring protection mechanism".
>
> * In a general ring topology, *any* recovery mechanism may be used.
> This may be the underlying transport's BLSR/MSSPRING or
> UPSR/SNCPRING, or it may be using control plane to set up 1+1 or 1:1.
> * In a BLSR/MSSPRING ring, the type of protection has already been
> decided (i.e., BLSR *is* the name of the protection mechanism).
> Similarly for UPSR/SNCPRING.
>
> Thus if we're talking about BLSR/UPSR rings, then the question is: how
> does the control plane protocols interact (do they interact?) with the
> underlying BLSR/UPSR, e.g., does the control plane simply treat the
> *entire* ring as a single node and thus interfaces to existing EMSs to
> ask for a sub-network connection across the "node", or does the control
> plane actually see all nodes of the ring and ask individual nodes for an
> STS-1/VC-3 connection (but note it only asks for the normal channel i.e.
> one connection, since the protection channel comes by default -- the
> service is either protected or unprotected but one connection in either
> case)...
>
> Zhi
>
> R. Muralidharan wrote:
>
> >Hi All,
> >
> >My understanding is as follows:
> >
> > BLSR or UPSR rings may be already provisioned in the SONET network. The
> >task using GMPLS is to set up an end to end virtual path, may be
> >encompassing multiple SONET rings. This virtual path set up is dynamic in
> >nature and the life of the path may be only for a fixed interval, after
> >which it would be tore down. When one wants to set up a path through a SONET
> >ring, one may have to specify whether one wants a 1+1 protection path or a
> >1:N protection path or just an unprotected path. Based on this specification
> >the GMPLS can discover and set up an appropriate path in a BLSR or an UPSR
> >ring as the case may be and hence the cost would be optimum. ( assuming that
> >a 1+1 path would cost more than an unprotected path). As Greg pointed out, I
> >also believe that the BLSR and UPSR ring configurations would already have
> >been set up by associated NMS or EMS and advertised. The granularity of the
> >path that can be set up using GMPLS could a VT1.5 or multiples of them ( VT
> >Path) or STS-1s (STS Path).
> >
> >I have used the words "path" and "virtual path" in generic terms and not in
> >the SONET or SDH domain definitions.
> >
> >Does the above make sense ?
> >regards,
> >murali
> >OSS Systems India
> >
> >----- Original Message -----
> >From: "Bernstein, Greg" <GregB@ciena.com>
> >To: "'Manoj Agiwal'" <ManojA@netbrahma.com>; "'Ccamp (E-mail)"
> ><ccamp@ops.ietf.org>
> >Cc: "mpls@UU. NET (E-mail)" <mpls@UU.NET>
> >Sent: Wednesday, May 29, 2002 10:28 PM
> >Subject: RE: Sonet Ring provisioning
> >
> >
> >
> >
> >>Hi Manoj, the UPSR and BLSR cases are very different. I'm assuming that
> >>
> >>
> >you
> >
> >
> >>are setting up SONET paths such as STS-1, STS-3c, ... STS-192c or their
> >>
> >>
> >SDH
> >
> >
> >>equivalent.
> >>Then
> >>(1) In the BLSR case the protection is at the SONET line layer, i.e.,
> >>
> >>
> >below
> >
> >
> >>the layer of the connection that you are setting up(SONET/SDH are layered
> >>networks). In this case no special action needs to be taken unless of
> >>course the entity requesting the connection asked for "enhanced"
> >>
> >>
> >protection
> >
> >
> >>in the setup request.
> >>
> >>(2) A UPSR works at the path layer, i.e., like a path layer 1+1, with the
> >>redundant paths taking different routes around the ring. Hence you are
> >>actually setting up two connections that have a special relationship with
> >>each other. This would have to be indicated somehow (tunnel ID or
> >>something). Some UPSRs may put constraints on the timeslots used too. One
> >>meta question is why bother signaling around a UPSR versus talking to a
> >>
> >>
> >UPSR
> >
> >
> >>as a separate "protection domain"? There is no way mesh restoration could
> >>come close to a UPSR's restoration speed (it just selects the better of
> >>
> >>
> >two
> >
> >
> >>signals). Hence I don't understand the benefit signaling around the ring
> >>
> >>
> >in
> >
> >
> >>this case, all vendors have methods for setting up their UPSRs via EMS's
> >>
> >>
> >why
> >
> >
> >>not just interface to those rather than to the individual ring elements...
> >>
> >>Greg B.
> >>
> >>***********************************
> >>Dr. Greg M. Bernstein
> >>Senior Technology Director, Ciena Corporation
> >>
> >>
> >>-----Original Message-----
> >>From: Manoj Agiwal [mailto:ManojA@netbrahma.com]
> >>Sent: Wednesday, May 29, 2002 2:01 AM
> >>To: 'Ccamp (E-mail)
> >>Cc: mpls@UU. NET (E-mail)
> >>Subject: Sonet Ring provisioning
> >>
> >>
> >>Hi ,
> >> Do we use GMPLS signaling protocol for configuring Sonet Rings (
> >>
> >>
> >UPSR
> >
> >
> >>/ BLSR ( 2 fiber/4
> >> fiber ) ?
> >>
> >> I was going through certain white papers where there was a mention
> >>that GMPLS is used as
> >> a signaling protocol for provisioning mesh topologies only
> >>.Traditional Sonet rings will be
> >> replaced by mesh topologies in future .
> >>
> >> But there is a section 12.( LSP protection and restoration) in GMPLS
> >>Architecture which says
> >> that " Both mesh and ring like topologies are supported "
> >>
> >> How do we provision nodes in Sonet ring using GMPLS ?
> >> Or GMPLS has been designed to provision mesh topologies only.
> >>
> >>Regards ,
> >>Manoj
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> >