This is how I think it *should* work, and please correct me if I'm wrong....
If the SONET protection switch is successful, the MPLS layer will never know
or care that there was a SONET protection switch, and it doesn't need to
know that there SONET protection is configured. MPLS protection, or
re-routing at any layer higher than SONET, should only kick in if a link
fails, meaning that SONET protection was unsuccessful or not configured.
>From MPLS' point of view, SONET protection (or any other protection at the
transport level) is completely transparent.
You can provision both schemes at the same time. However, MPLS protection
will probably not be useful on a point to point link... MPLS protection will
be useful throughout your whole network where it can reroute around broken
and links nodes, while SONET protection will protect your point to point
links so that your MPLS protection doesn't even have to kick in.
Hope this helps,
Aleksander Zawisza
Nortel Networks, Juniper Global Technical Support
* 613-768-4089 / ESN 398-4089
* zawisza@nortelnetworks.com
* http://gts/departments/juniper
-----Original Message-----
From: Yongseok Park [mailto:yongseok@coreenetworks.com]
Sent: July 24, 2001 5:58 PM
To: gandhi
Cc: juniper-nsp
Subject: RE: SONET APS and MPLS link protection
Hi, thanks for the kind answer.
However, I don't think that my question was really answered. My question
was regarding Juniper's specific implementation of inter-layer
protection. If we have both MPLS link protection and SONET 1:1 on a
link, which will be kicked off first? Does MPLS link protection process
check if SONET protection is provisioned, and then ignores MPLS link
protection or wait to see if SONET APS was successful or not? Or will
the provisioning of both protection schemes on a link be disallowd?
Could you also give pointers to this issue?
Thanks a lot.
yongseok
> -----Original Message-----
> From: Arun Gandhi [mailto:gandhi@juniper.net]
> Sent: Wednesday, July 18, 2001 10:48 AM
> To: Yongseok Park
> Cc: juniper-nsp@puck.nether.net
> Subject: RE: SONET APS and MPLS link protection
>
>
>
> Hi,
>
> Thats an interesting question - I'll try to answer from whatever
> research/work I have done on protection/restoration in
> school. TO ALL -
> Please correct me if you have a different opinion/explaination.
>
> Remember that SONET is a physical layer protection mechanism
> so it will
> detect first as against MPLS protection which is L2/L3
> (shim). Eventually
> both will. We know that SONET provides restoration to *50ms*
> but is limited
> to *ring topologies*. It uses extra/more
> resources (which it reserves) than required for protection.
> SONET's APS will
> try to switch the traffic stream but will not take care of packet
> loss/reordering.
>
> In MPLS, when an LSP is teared down via a link going down,
> traffic stream is
> to switched to an alternate LSP established on demand (at run
> time) or a
> preconfigured LSP using a *Faliure Indication Signal (FIS)*. Packet
> reordering is a critical issue because it would degrade (i.e.
> increase) the
> overall restoration/protection time as detection of
> out-of-order packets is
> detected at destination and at the transport layer. So you see the
> additional work/time involved. And MPLS layer will take care
> of packets
> being reordered. (using signaling or other mechanism). Well,
> this is a very
> interesting issue and lot of people are looking into it since
> MPLS claims
> "to provide protection/restoration comparable to SONET (50ms)".
>
> I am not sure how far I have answered your question or
> confused you. I have
> done/doing some research (experiments, simulatons w/different
> traffic types)
> in this area and if you are interested could point you to my notes.
>
> Please let me know if I can clearify anything I have mentioned above.
>
> Thanks,
> Arun
>
>
> -----Original Message-----
> From: Yongseok Park [mailto:yongseok@coreenetworks.com]
> Sent: Wednesday, July 18, 2001 7:03 AM
> To: juniper-nsp@puck.nether.net
> Subject: SONET APS and MPLS link protection
>
>
> Hi, suppose that someone provisions both SONET APS and MPLS link
> protection for a link. When the link goes down, what would happen?
>
>
>
>
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