Protection in OBS

Protection in OBS Zartash Afzal Uzmi

First slide… This is not a tutorial! This is a discussion Lahore University of Management Sciences

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 Lahore University of Management Sciences

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) Lahore University of Management Sciences

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! Label IP Datagram Lahore University of Management Sciences

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 Label Label IP Datagram Lahore University of Management Sciences

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? Lahore University of Management Sciences

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! Lahore University of Management Sciences

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 Lahore University of Management Sciences

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 Lahore University of Management Sciences

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 Lahore University of Management Sciences

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! Lahore University of Management Sciences

Last slide… Discussion! Lahore University of Management Sciences

Protection in OBS