1) MPLS introduces labels that are prefixed to packet headers and allows forwarding based on these labels instead of long IP addresses, enabling traffic engineering. 2) Labels are assigned based on forward equivalence classes which group packets that should follow the same path. This path is called a label switched path (LSP). 3) Generalized MPLS (GMPLS) extends MPLS to support a wider range of network types and interfaces beyond IP routers, including support for optical and time-division multiplexing networks. It enhances signaling protocols and introduces hierarchical LSP setup.

1. Internet Traffic Engineering Using Multi-Protocol Label Switching (MPLS)D.O. Awduche and B. JabbariGeneralized Multi-Protocol Label Switching: An Overview of Signaling Enhancements and Recovery TechniquesA. Banerjee et. al.Internet Traffic EngineeringJoachim Seilfaldet (joachse)Jonas Sæther Markussen (jonassm)

2. Multiprotocol Label SwitchingJonas Sæther Markussen

3. AgendaMulti-Protocol Label SwitchingOverviewLabelsLabel assignmentForward equivalence classes (FECs)Label switched forwarding (LSP)Control and data separationGeneralized Multi-Protocol Label SwitchingTraffic EngineeringTraffic Engineering using MPLS

4. Overview (1)Multiprotocol Label Switching Architecture (RFC3031)Overlay link network (OSI layer “2.5”)Eliminates the dependence on a specific link layer technology (e.g. ATM, SONET, etc.)Eliminates the need for multiple layer 2 networks to support multiple protocolsMPLS can carry many different kinds of traffic: IP, ATM, SONET, Ethernet frames, etc.Constraint-based forwarding(Optional) assignment of labels prefixing packet headersForwarding no longer constricted to packet destination only

5. Overview (2)Introduces connection-oriented routing to legacy IP routersDoes this by establishing “virtual links” using label switched paths (LSPs)Provides means for traffic engineering (TE)Can manipulate link-state advertisements (LSAs)An easy-to-maintain virtual topologyWith TE, MPLS can establish alternative paths to avoid congested areasEnables fault tolerance if a link goes down

6. LabelsMPLS introduces labelsOriginally called “tags” in earlier works by Cisco and othersFixed-size header20-bit Label Value3-bit Traffic Class (QoS priority and ECN)1-bit Bottom-of-Stack flag8-bit Time-to-LiveUnlike ATM and frame relay, labels can be stackedAllowing hierarchical arrangement of framesLabels are prefixed to IP headers and to each otherEnables fast look-ups (more on this later)

7. Label assignment (1)Packets enter a MPLS domain through an ingress node and leaves through an egress nodeThese are typically label edge routers (LERs)Ingress nodes assigns (pushes) to and egress nodes removes (pops) labels from packets coming inEntry nodeExit nodeLERLERMPLS domain

8. Label assignment (2)Three label operations:Push (impose, assign)Encapsulates the packet in a new MPLS layerAllows hierarchical routingUsed by e.g. MPLS VPN (L3VPN)Pop (dispose, remove)Remove uppermost labelWhen the last label is popped, the packet “leaves” the MPLS tunnel/domainUsually done by the egress router (exit node)Can be done by the preceding LSR for offloading the egress router  penultimate hop popping (PHP)SwapSimply replaces the label and forwards packet along the path associated with the new label

9. Forward equivalence classesLabel assignment is based on forward equivalence classes (FECs)Packets belonging to the same FEC has the same labelsFECs can be defined differently:Based on enter (ingress) nodes and exit (egress) nodesBased on service class, requiring similar QoS or packet treatment across the MPLS domainPackets belonging to the same flowCombinations of those aboveFECs are associated according to some policy formulationPackets belonging to the same FEC traverse through the same path (or multi-paths)This is called a label switched path (LSP)

10. Label switched forwarding (1)“Virtual links” presented to above layers in the OSI stackThese are called label switched paths (LSPs)From one label edge router (LER) to anotherTypically the same as ingress and egress nodesEstablished (and tore down) by a signaling protocol (more on this later)This introduces connection-orientation in networks that originally were based on packet switching (PS)  unified data carrying for both PS and circuit-basedRouters in the MPLS domain that forward both labeled packets and conventional IP packets are called label switching routers (LSRs)Label edge routers (LERs) are usually LSRs with label stacking functionalityLERLink from IP perspectivePhys. linksRouterLERLSRLSRRouterLSP paths

11. Label switched forwarding (2)LSP update policy can vary:Predefined (strategic)Careful planning of the virtual topologyConsiderations and forecasting to traffic patternsHow, when and where to activate new LSPs to address performance issues in the networkAd-hoc (tactical)Establishment and managing of LSPs to divert traffic away from congested network resources to under-utilized alternativesA “hybrid approach”: LSPs control traffic parts in some segments of network while interior gateway routing protocol metrics are used in other

12. Control and data separation (1)MPLS functionality is separated into two “planes” with different purposesThe planes are decoupled and independentClear separation of the control plane from the data plane in network switching elementsEven further separation in Generalized MPLS (GMPLS)Protocol TransactionsBearer ChannelsFrom the article, Fig. 3

13. Control and data separation (2)Control planeControl protocols are software processes that communicate across node boundariesDistribute and manage:Network topologyResource availabilityEstablish and tear down LSPsSignaling protocolLabel distribution protocol (LDP) for best-effort hop-to-hop pathsRSVP-TE (or CR-LDP) for traffic engineering purposes and end-to-end virtual circuits

14. Control and data separation (3)Forwarding planeLabel swapping operationsLook-up tablesPacket treatment functionsSchedulingQueue managementRate shapingPolicingUsually implemented in hardwareHigh speed operations

15. Generalized Multi-Protocol Label SwitchingJoachim Seilfaldet

16. AgendaMulti-Protocol Label SwitchingGeneralized Multi-Protocol Label SwitchingWhat is GMPLS?Implemented interfaces to supportEnhancements to SignalingHierarchical LSP SetupGMPLS Protection and Restoration TechniquesPath SwitchingLine SwitchingProtection MechanismsRestoration MechanismsTraffic EngineeringTraffic Engineering using MPLS

17. What is GMPLS?Multi-Protocol Label Switching RecapWorks as an extension of IP

18. Control plane is logically separated from data plane.

19. Referred as a “Layer 2.5” protocol. Layer 2 (Data Link Layer) and Layer 3 (Network Layer).Generalized Multi-Protocol Label SwitchingNext generation implementation of Multi-Protocol Label Switching

20. Extends to support a wide range of LSP for different network devices.

21. Extensions made to IP router protocols (OSPF and IS-IS)

22. New Link Management ProtocolWhat is GMPLS?Control plane concepts can be used in other switched transport technologiesPacket Switched Networks

23. A label represent a short tag attached to packet

24. Time-Division Multiplexing Networks

25. A label represent a time slot

26. Wavelength-Switched Networks

27. A label represent a wavelength

28. Fiber-switched Networks

29. A label represent a fiberImplemented interfaces to supportPacket Switch Capable Interfaces (PSC)

30. If a node recives data over this interface, it will be able to switch the recived data on a packet-by-packet basis based on the label attached.

31. Time-Division Multiplexing (TDM)

32. Will be able to multiplex or de-multiplex channels within an payload.

33. Lambda Switch Capable Interface (LSC)

34. Will be able to recognize and switch individual lambdas within the interface.

35. Fiber Switch Capable Interface (FSC)Will be able to switch the entire contents to another interface (without distinguishing lambdas, channels or packets), such as optical cross-connects (OXCs) .

36. Enhancements to SignalingGMPLS require LSP start and end on similar device

37. For example, SONET TDM.

38. Necessitates a separate control plane transport network.

39. GMPLS is extended to allow control plane to be physically diverse from the associated data plan.Enhancements have been made to the label distribution protocol RSVP-TE to support GMPLS.

40. Hierarchical LSP SetupOccurs when a new LSP is tunneled inside an existing higher-order LSP

41. Serves as a link through other LSP

42. Nodes at border of regions are responsible for forming higher-order LSP and aggregating lower-order LSPs.Hierarchical LSP SetupFigure shows how hierarchical LSP setup is performed over different types of network types.

43. Hierarchical LSP SetupTimelineR0R1S2O3P4P5P6O7S8R9R10Path 1Path 2Path 3Path 4Resv 4LSP4 completesResv 3LSP3 completesResv 2LSP2 completesResv 1LSP1 completes

44. GMPLS Protection and Restoration TechniquesProtection and restoration is addressed using two techniquesPath Switching

45. Line SwitchingFault management consist ofDetection

46. Localization

47. Notification

48. Mitigation (Done with protection and restoration)Protection MechanismsEfficient use of protection requiresDistribution of relevant link properties

49. Protection bandwidth

50. Protection capabilities

51. Establish secondary paths through network

52. Signal switch from primary path to backup Path SwitchingFailure is addressed at path endpoints.Path protectionProtection path is pre-allocated.

53. Resources for protection path is reserved, specifically to handle traffic from path that is protected.Path restorationRestoration of path needs to happen “on-the-fly” or to be pre-computed and cached at endpoints.

54. No resources are reserved in case of a failure.Line SwitchingFailure is addressed at transit node, where failure is detected.Span ProtectionTraffic is switched to an alternate parallel channel or link connecting same two nodes.Line RestorationTraffic is switched to an alternate route between two failing nodes. Passing through additional intermediate nodes.Protection Mechanisms1+1 protectionData transmitted simultaneously over two paths.