Abstract
An important requirement in the IP-based control of time-division multiplexing
(TDM) optical transport networks is to utilize the in-built protection capabilities
of synchronous optical network (SONET) unidirectional path-switched rings (UPSRs)
and to automate the UPSR-protected path setup in mixed mesh–ring networks. This
requires modifications to existing IP signaling and routing protocols and new
processing rules at the network nodes. Here we leverage IP routing and signaling and
multiprotocol label switching (MPLS) fast-reroute techniques for accurately
advertising UPSR ring topologies to remote nodes and dynamically establishing
UPSR-protected paths across a transport network. Our proposal also makes a NUT1-like
(nonpreemptible unprotected traffic) feature possible in UPSRs, which allows for
efficient utilization of UPSR protection bandwidth. We achieve this by encoding
UPSR-specific information in the open shortest-path-first (OSPF) link state
advertisements and in signaling messages of the Resource Reservation Protocol (RSVP)
with TE extensions. In addition, we modify the signaling and routing state machines
at the nodes to interpret and process this information to perform UPSR topology
discovery and path computation. The uniqueness of our proposals is that the
algorithms and the rules specified here allow for existing IP-based protocols [such
as those within the generalized MPLS (GMPLS) framework, which currently applies to
mesh networks] to be efficiently adapted for this context while still achieving our
objective of exploiting UPSR-protection capabilities.
© 2002 Optical Society of America
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