Protection in OBS Zartash Afzal Uzmi

Jan 13, 2006Lahore University of Management Sciences2 First slide… This is not a tutorial! This is a discussion

Jan 13, 2006Lahore University of Management Sciences3 Outline More MPLS Labels Stacking labels GMPLS Protection in Optical Burst Switching (OBS) Restoration and Protection Protection in OBS Protection in MPLS+OBS (labeled OBS) Food for thought

Jan 13, 2006Lahore University of Management Sciences4 Outline More MPLS Labels Stacking labels GMPLS Protection in Optical Burst Switching (OBS) Restoration and Protection Protection in OBS Protection in MPLS+OBS (labeled OBS) Food for thought

Jan 13, 2006Lahore University of Management Sciences5 IP versus MPLS In IP Routing, each router makes its own routing and forwarding decisions In MPLS: source router makes the routing decision Routing : finding shortest path to destination! Intermediate routers make forwarding decisions A path is computed and a “virtual circuit” is established from ingress router to egress router An MPLS path or virtual circuit from source to destination is called an LSP (label switched path)

Jan 13, 2006Lahore University of Management Sciences6 MPLS Forwarding In MPLS, a label is attached with IP datagrams at the ingress router Intermediate MPLS routers make forwarding decision based on the label You can even stack the labels! IP DatagramLabel

Jan 13, 2006Lahore University of Management Sciences7 MPLS Label Stacking Label stacking is useful for aggregating traffic It is also useful in n:1 protection routing Intermediate MPLS routers usually look at the topmost label IP DatagramLabel

Jan 13, 2006Lahore University of Management Sciences8 Generalized MPLS (GMPLS) In MPLS, label is a sequence of bits and is attached with the IP packet MPLS  Forwarding is decided by the label Forwarding may be decided based on: Time slot Wavelength Incoming port These all are examples of GMPLS Forwarding based on burst control packet?

Jan 13, 2006Lahore University of Management Sciences9 Outline More MPLS Labels Stacking labels GMPLS Protection in Optical Burst Switching (OBS) Restoration and Protection Protection in OBS Protection in MPLS+OBS (labeled OBS) Food for thought

Jan 13, 2006Lahore University of Management Sciences10 Protection and Restoration Restoration On-demand recovery – no preset backup paths Example: existing recovery in IP networks Protection Pre-determined recovery – backup paths “in advance” Primary and backup are provisioned at the same time IP supports restoration Because it is datagram service MPLS supports restoration as well as protection Because it is virtual-circuit service What should be used in OBS? Restoration? Burst is too fast to sustain restoration latency…NO!

Jan 13, 2006Lahore University of Management Sciences11 Protection in OBS 1:1 or n:1 protection is useful for “circuits” Either optical circuits or virtual circuits or the LSPs In non-circuit architectures such as OBS Usually 1+1 protection is used Other schemes are also possible

Jan 13, 2006Lahore University of Management Sciences12 Outline More MPLS Labels Stacking labels GMPLS Protection in Optical Burst Switching (OBS) Restoration and Protection Protection in OBS Protection in MPLS+OBS (labeled OBS) Food for thought

Jan 13, 2006Lahore University of Management Sciences13 MPLS+OBS In MPLS+OBS Two LSPs are created for each incoming LSP request One LSP for the BCP One LSP for the Burst itself In GMPLS+OBS Switching can be on some basis Label associated with the IP packet (Labeled OBS) Anything else such as wavelength, timeslot, port, etc. Labeled-OBS is a special case of GMPLS+OBS

Jan 13, 2006Lahore University of Management Sciences14 GMPLS: out-of-band signaling GMPLS control channel Routing Signaling Link management These functions use IP based Routing/forwarding GMPLS data channel Typically label-swapped Can be wavelength-swapped, fiber-swapped, etc. Both BCP and Burst use the data channel

Jan 13, 2006Lahore University of Management Sciences15 GMPLS+OBS and Faults Labeled OBS is a specific case of GMPLS+OBS What happens in case of fault? Both BCP and Burst need re-routing May lead to longer paths Offset may not be enough If only BCP path fails Recovery time is extremely important Recovery time at a node is included in processing time Only local protection makes sense! What if only Burst path fails? If Burst path not recoverable, then BCP should be dropped!

Jan 13, 2006Lahore University of Management Sciences16 Last slide… Discussion!