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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