Leveraging IP signaling and routing to manage UPSR-based transport networks

An important requirement in the IP-based control of TDM optical transport networks is to utilize the built-in protection capabilities of SONET unidirectional path switched rings (UPSRs) and automate UPSR protected path setup in mixed mesh-ring networks. This requires modifications to existing IP signaling and routing protocol and new processing rules at the network nodes. In this paper, we leverage IP routing and signaling, and MPLS fast-reroute techniques to accurately advertise UPSR ring topologies and dynamically establish UPSR protected paths across a transport network. Our proposal also makes a NUT-like (non-preemptable 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 advertisement 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 in the paper allow for existing IP-based protocols (such as those within the 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.