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IEEE Communications Magazine July 2001

Generalized Multiprotocol Label Switching: An Overview of Signaling Enhancements and Recovery Techniques. IEEE Communications Magazine July 2001. Outline. Introduction Enhancements to Signaling GMPLS Protection & Restoration Techniques Conclusions. Introduction (1/3). MPLS is based on

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IEEE Communications Magazine July 2001

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  1. Generalized Multiprotocol Label Switching: An Overview of Signaling Enhancements and Recovery Techniques IEEE Communications Magazine July 2001

  2. Outline • Introduction • Enhancements to Signaling • GMPLS Protection & Restoration Techniques • Conclusions

  3. Introduction (1/3) • MPLS is based on • Separation of forwarding information (label) from the content of the IP header • Use of a single forwarding paradigm at data plane to support multiple routing paradigms at control plane • Use of different technologies and link layer mechanisms to realize label swapping forwarding paradigm • Flexibility in the formation of forwarding equivalence classes (FECs) • The concept of a forwarding hierarchy via label stacking

  4. Introduction (2/3) • Recent work: extend MPLS control plane, specifically MPLS constraint-based routing, from routers/ATM switches to optical crossconnects • Using MPLS as the foundation for connection establishment and a common control plane • Simplify network operations and management • Provide a wide range of deployment scenarios, ranging from overlay to peer • Reuse and extend existing routing and signaling protocols thus minimizing risks and reducing time to market for advanced optical switching equipment

  5. Introduction (3/3) • GMPLS: extensions to MPLS • Enhancements to RSVP-TE and CR-LDP signaling protocols for optical transport networks • Enhancements to OSPF and IS-IS IGPs to advertise availability of optical resources in the network • A new link management protocol for optical networks • Ability to establish bidirectional connections in a single request • Ability of fault isolation, fault localization, fault notification and fault mitigation

  6. Enhancements to Signaling • Enhancements to the label distribution protocols, RSVP-TE and CR-LDP • Hierarchical LSP Setup • The Suggested Label • Bidirectional LSP Setup • Notify Messages

  7. Hierarchical LSP Setup (1/2)

  8. Hierarchical LSP Setup (2/2)

  9. The Suggested Label • GMPLS allows a label to be suggested by an upstream node • Valuable when set up a bidirectional LSP using paired Tx and Rx interfaces to the same physical port • Useful in optical subnetworks with limited wavelength conversion capability • Permit an upstream node along a service path to start hardware configuration before the downstream node communicates a label to it • Downstream node may reject the suggested label and pass a different label upstream, the upstream node must accept the label

  10. Bidirectional LSP Setup • LSPs in basic MPLS architecture are unidirectional, a bidirectional LSP uses two unidirectional LSP in opposite directions • Increased setup latency for LSP establishment • Twice the control overhead • Complicated route selection • Difficult to provide a clean interface for SONET equipment which may rely on bidirectional hop-by-hop paths for protection switching • Use of a single set of Path/Request and Resv/ Mapping messages to establish bidirectional LSPs

  11. Notify Messages • A node passing transit connections should be able to notify the node responsible for restoring the connections when failures occur • The Notify message has been added to RSVP-TE for GMPLS to provide a mechanism for informing nonadjacent nodes of LSP-related failures • Application: to notify when the control plane of a link fails but the data plane (LSP) is still functional, such link is referred to as degraded link

  12. GMPLS Protection and Restoration Techniques

  13. Protection Mechanisms (1/3) • Nomenclature • 1+1 protection: payload data transmitted over two disjoint path and a selector at receiving node • M:N protection: M preallocated backup paths shared between N primary paths • 1:N protection • 1:1 pretection • Mechanisms • Span Protection • Path Protection

  14. Protection Mechanisms (2/3)

  15. Protection Mechanisms (3/3)

  16. Restoration Mechanisms (1/2) • Line restoration • A new path is selected at an intermediate node • Beneficial for connections spanning multiple hops and/or large distances • May break TE requirements • Path restoration • The new path is selected at the source node • Alternate routes may be precomputed by the head-end of the connection and cached for future use • May reuse nodes in the original path

  17. Restoration Mechanisms (2/2)

  18. Conclusions • GMPLS will constitute an integral part of next-generation data and optical networks. • The functionality delivered by GMPLS allows network operators to scale their network well beyond current limitations. • The signaling capabilities of GMPLS will allow service providers to quickly build out high-capacity agile infrastructures. • Flexible M:N protection and restoration capabilities of GMPLS allow efficient addressing of network survivability.

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