(Slide set by Norvald Stol/Steinar Bjørnstad 2013)

Outline Introduction Enhancements to signaling - Hierarchical LSP setup - The suggested label - Bidirectional LSP setup - Notify messages GMPLS protection and Restoration techniques - Protection mechanisms (Span/Path protection) - Restoration mechanisms Conclusions

Introduction IP -> MPLS => Datagram to Virtual Connection (VC) (point-to-point) Explicitly routed label switched paths (LSPs) established before information transport – independent of actual routing paradigm Label swapping used as forwarding paradigm Forwarding equivalence classes (FECs) Label hierarchy / Label stacking

Introduction (2) Constraint based routing - traffic engineering (QoS differentiation) - fast reroute (after failure) - diversity routing (disjoint alternative paths for protection) Routing protocols (e.g. OSPF) must exchange sufficient information for ”constraint” Resource reservation protocol with traffic engineering (RSVP-TE) is used to establish LSP/label forwarding states along path. (The alternative CR-LDP is not used any more)

Introduction (3) Generalized MPLS: Extensions to handle e.g. optical network resources (OXC’s) (e.g. extensions of OSPF, RSVP-TE). Common control plane for packet and optical network New Link Management Protocol (LMP) for optical links. Support for (label) switching in time, wavelength and space domains – and a label hierarchy. Additional functionality to handle bidirectional links and protection/restoration.

RSVP-TE and OSPF enhancements RSVP-TE (CR-LDP) Initiate optical channel trails For optical networks and other connection oriented networks OSPF (IS-IS) Advertise availability of resources Bandwidth of wavelengths Interface types Other network attributes and constraints

Enhancements to signaling Control plane may be physically diverse from the data plane. Hierarchical LSPs  (Study the example in the article to see what establishing a new LSP may entail, start with LSP1) The suggested label: An upstream node suggests an optimal label (fast) May be overridden by its downstream node (slower) - In optical networks with limited wavelength conversion Suggested wavelength (-label) to use is very useful

Enhancements to signaling (2) Bidirectional LSP setup (New in GMPLS): Bidirectional optical LSPs (lightpaths) are important for network operators Fate sharing Protection and restoration Same QoS in both directions, same resource demands Problems with two independent LSPs in MPLS: Additional delay in set-up (problem in protection) Race conditions for scarce resources => lower probability of success for both directions simultaneously Twice the control overhead In GMPLS: Single set of Path/Request and Resv/Mapping messages used to establish LSPs in both directions at once.

Enhancements to signaling (3) Notify messages: Added to RSVP-TE for GMPLS Provides a mechanism for informing nonadjacent nodes of LSP-related failures. Inform nodes responsible for restoring connection Avoid processing in intermediate nodes Speed up Failure detection and reaction Re-establishment of normal operation

GMPLS Protection and Restoration Four primary steps of fault management: Detection - should be handled at layer closest to failure, i.e. optical layer. E.g. ”Loss-of-light” (LOL), Bit Error Ratio, .. Localization - requires communication between nodes. LMP includes procedure for fault localization. Channel fail message over separate control channel Notification - Notify message added to RSVP-TE signaling Mitigation “Repairing the failure”

GMPLS Protection and Restoration (2) Path switching (End-to-end) Failures addressed at path end-points Line switching (local) Action at intermediate transit nodes where the failure is detected Prot and rest. Terms not precisely defined: In practice used for fault handling in different time frames. ”Protection” Fast usually pre-allocated resources to handle failures quickly, e.g. SDH/SONET: 50 ms – 100% extra resources and simultaneous transmission. (1+1 protection)

GMPLS Restoration When fault is handled after a failure has occurred Dynamic resource allocation Usually at least one order of magnitude higher delay than protection Different levels of ”preparedness” Pre-calculated routes or not; Some resources reserved or not

GMPLS Protection and Restoration (3) Protection mechanisms: 1+1 protection: simultaneous transmission of data on two different paths. M:N protection: M preallocated back-up paths shared by N connections. (1:N is most usual; 1:1 also relevant). Span protection – between adjacent nodes (NB! Avoid ”fate sharing”):

GMPLS Protection and Restoration (4) 1+1 Path protection (disjoint paths): For M:N Path protection: back-up paths may be used for lower priority traffic in normal operation – preemption (Supported by GMPLS)

GMPLS Protection and Restoration (5) Restoration mechanisms: Alternative paths may be computed beforehand, but resources are seldom allocated before they are needed.

Conclusion GMPLS is a good idea and do have a lot of nice functionality to handle the networks of the future!