An introduction to MPLS and GMPLS (and briefly T-MPLS)

1. An introduction to MPLS and GMPLS (and briefly T-MPLS) Anne-Grethe Kåråsen, Telenor R&I Modified by Steinar Bjørnstad NTNU Two slides on T-MPLS added by Norvald Stol NTNU 2007

2. Why was MultiProtocol Label Switching (MPLS) designed? • To enhance the performance of the traffic forwarding mechanisms (compared to traditional IP forwarding) • To provide a traffic engineering (TE) capability in IP networks

3. What is Traffic Engineering (TE)? • TE is concerned with performance optimization of operational networks. • Traffic performance: A major goal of Internet TE is to facilitate efficient and reliable network operations while simultaneously optimizing network resource utilization and traffic performance. • QoS: Traffic oriented performance objectives include the aspects that enhance the QoS of traffic streams. • Resource utilization: Resource oriented performance objectives include the aspects pertaining to the optimization of resource utilization.

4. The resource problem to solve: • Conventional IGP path computation is selected based upon a simple additive metric. • Bandwidth availability is not taken into account • Some links may be underutilized while others are congested.

5. A solution to the resource problem Path for R1 to R3 traffic Path for R2 to R3 traffic

6. MPLS - some main concepts • Uses label switching to forward data • A label is a short fixed length physicallycontiguous identifier which is used toidentify a FEC, usually of local significance. • MPLS path = Label Switched Path (LSP) • Forwarding Equivalence Class (FEC) • A group of IP packets that are forwarded in the same manner • FEC – label mapping in ingress MPLS node • Criteria for assigning packets to FECs are configurable • Next Hop Label Forwarding Entry (NHLFE) • Packets next hop + label operation (swap, push, pop)

7. The MPLS shim header • The EXP Field is "Experimental" though it is proposed use is to indicate Per Hop Behavior of labeled packets traversing Label Switching Routers. (QoS) • The Stack (S) Field indicates the presence of a label stack. • The Time to Live Field is decremented at each LSR hop and is used to throw away looping packets.

8. LSP route determination • An LSP must be set up and labels assigned at each hop before traffic forwarding can take place. • There are two kinds of LSPs, based on the method used for determining the route: • control-driven LSPs (hop-by-hop LSPs) • explicitly routed LSPs (ER-LSPs) • A control-driven LSP follows the path that a packet using default IP routing would have used. • An ER-LSP may be specified and controlled so that the network traffic follows a path independent of what is computed by IP routing.

9. Constraint-based routing • Types of constraints: • Resource related (e.g. bandwidth) • Administrative (e.g. include/exclude certain links) • Resource related and policy related attributes are associated with links. • Link attributes are flooded by the routing protocols along with topology information. • A constraint-based path computation process uses this information when finding paths that satisfy given constraints. • Most used algorithm is Constraint Shortest Path First (CSPF): • Excludes all links that fail to meet constraint • Chooses shortest path that meets constraint • Convenient for online path selection, one LSP at a time

10. ER-LSPs • Explicit LSP: route is determined at the originating node. When we explicitly route an LSP, we call it an LSP tunnel or a traffic-engineering tunnel. • Explicit route information is carried only at the time of LSP setup, not with each packet forwarded on the LSP. • LSP tunnels are uni-directional. • Can be set up manually or by the use of a signaling protocol.

11. LSR9 LSR8 LSR3 LSR4 LSR2 ERO=( 5) ERO=(2, 6, 7, 4, 5) ERO=(4, 5) LSR5 ERO=(6, 7, 4, 5) L=21 L=5 ERO=(7, 4, 5) L=10 L=14 LSR1 LSR7 L=21 LSR6 RSVP Path message carried Explicit Route Object (ERO) RSVP Resv message carries Label information (L) ER-LSP setup example using RSVP-TE

12. Label-Switched Path (LSP) LER IP Packet Label 1 Label 2 Label 3 IP Packet LER LSR LSR IP Packet IP Packet IP Packet IP Forwarding LABEL SWITCHING IP Forwarding MPLS Label Forwarding Example

13. Label stacking

14. Protocols for MPLS routing and signaling Routing: • Open Shortest Path First (OSPF) & Intermediate System –Intermediate System (IS-IS) with TE extensions Signaling: • Label Distribution Protocol (LDP) [RFC 3036] • Constraint based LDP (CR-LDP) [RFC 3212] • Extensions to Resource Reservation Protocol (RSVP) for LSP tunnels [RFC 3209] • Border Gateway Protocol (BGP) [RFC 3107]

15. MPLS references • Multiprotocol Label Switching Architecture, RFC 3031, Jan 2001 • Requirements for traffic engineering over MPLS, RFC 2702, Sept 1999 • Traffic engineering extensions to OSPF version 2, RFC 3630, September 2003 • Traffic Engineering Extensions to OSPF version 3, Internet Draft <draft-ietf-ospf-ospfv3-traffic-07>, April 2006 • IS-IS extensions for traffic engineering, RFC 3784, June 2004 • LDP specification, RFC 3036, Jan 2001 • Constraint-based LSP setup using LDP, RFC 3212, Jan 2002 • RSVP-TE: Extensions to RSVP for LSP tunnels, RFC 3209, Dec 2001 • Carrying label information in BGP-4, RFC 3107, May 2001

16. Generalized MultiProtocol Label Switching (GMPLS) • GMPLS is an enhanced version of the MPLS-concept. • GMPLS related work is coordinated by the IETF Common Control and Measurement Plane (ccamp) working group. • In data networks, MPLS covers both the control plane (label binding, label distribution, etc.) and the data plane (packet forwarding). • In circuit switched networks there is no packet forwarding. • Only MPLS control plane components are applicable to circuit switched networks. • GMPLS assumes IP-based routing and signaling protocols, and IP addresses. (IP-centric)

17. GMPLS (former MPlS) – mapping to OTN Main features applicable to OTN (Optical Transport Network) • MPLS control plane is implemented in each OXC • Constraint-based routing and signaling provide control plane for OXCs • to discover, distribute, and maintain relevant state information associated with the OTN • to establish and maintain OCh trails • Each OXC is considered an equivalent of a Label Switched Router (LSR) • Lightpaths (OCh trails) are considered similar to Label Switched Paths (LSPs) • Lambdas and switch ports are considered similar to labels

18. GMPLS – new set of LSP interfaces • Packet Switch Capable (PSC) interfaces: • Recognize packet boundaries and can forward data based on the content of the packet header (IP header, MPLS shim header). • Layer-2 Switch Capable (L2SC) interfaces: • Recognize frame/cell boundaries and can forward data based on the content of the frame/cell header (Ethernet MAC header, ATM VPI/VCI). • Time-Division Multiplex Capable (TDM) interfaces: • Forward data based on the data’s time slot in a repeating cycle (SDH/SONET, G.709 TDM, PDH). • Lambda Switch Capable (LSC) interfaces: • Forward data based on the wavelength on which the data is received (wavelength, waveband). • Fiber-Switch Capable (FSC) interfaces: • Forward data based on a position of the data in the real world physical spaces (port, fiber).

19. GMPLS control plane – functional components • Resource discovery and link management • The transaction that establishes, verifies, updates and maintains the LSR adjacencies and their port pair association for their transport (data) plane. • LSR level resource table: resource map that includes attributes, neighbor identifiers, and real-time operation states. • Routing • Topology information dissemination • Path selection • Signaling • LSP creation, modification, deletion, restoration, and exception handling

20. GMPLS – LSR level resource discovery and link management • Self resource awareness/discovery • As a result, the LSR resource table is populated with local ID, physical attributes, and logical constraints parameters • Neighbor discovery and port association • The process of discovering the status of local links to all neighbors by each LSR in the network, The up/down status of each link, link parameters, and the identity of the remote end of the link must be determined (periodical operation) [LMP]. • Resource verification and monitoring • Neighbor operation state detection and configuration verification (continuous operation). • Service negotiation/discovery • Covers all aspects related to service rules/policy negotiation between neighbors.

21. GMPLS - Routing • Topology information dissemination • Distribution of topology information through the network to form a consistent network level resource view among LSRs. • What type of information is required? • How is the information disseminated? • Triggering mechanisms for information update? • GMPLS assumes that an IP-based routing protocol is used for topology information dissemination. • GMPLS extensions have been defined for the TE extended versions of OSPF and IS-IS.

22. GMPLS – Routing cont. • Path selection • Usually a constraint-based computation process, resulting in an explicit route or source route. • Hop-by-hop routing is also possible. • Specific constraints on optical layer routing • Re-configurable (but blocking) network elements such as OADMs • Transmission impairments • Absence of wavelength conversion • Path diversity

23. GMPLS - IGP Extensions OSPF and IS-IS extensions to carry additional information: • switching capabilities of link (PSC, L2SC, TDM, LSC, FSC) • link encoding (e.g. SONET, SDH, GbE, etc.) • grouping of links that share same fate (SRLG) • protection capabilities of link • incoming and outgoing interface ID • CSPF extensions: • take into account new constraints (e.g. link encoding, multiplexing capabilities, etc.) • compute diverse paths • compute bi-directional paths

24. GMPLS - Signaling • GMPLS inherits all signaling functions from MPLS-TE: • LSP creation • LSP deletion • LSP modification • LSP exception handling • Additional GMPLS signaling protocol requirements: • Creation of bi-directional LSPs • Support of unnumbered links • Rapid failure notification • LSP fast restoration

25. GMPLS – signaling extensions • Generalized label request • Supports communication of characteristics required to support the LSP being requested, including LSP encoding, switching type, and LSP payload • LSP bandwidth encoding values, carried in a per protocol specific manner (e.g. in the CR-LDP Traffic Parameters TLV) • Generalized label • Extends the traditional label by allowing the representation of labels that identify time-slots, wavelengths, or space division multiplexed positions, or “anything that is sufficient to identify a traffic flow”. • Non-hierarchical label. • Support of waveband switching • A waveband represents a set of contiguous wavelengths that can be switched together to a new waveband. • Waveband label contains 3 fields: waveband ID, start label, end label. • Suggested label • Is used to provide a downstream node with the upstream node's label preference. • May reduce latency of LSP setup

26. GMPLS – signaling extensions cont. • Label set • Is used to limit the label choices of a downstream node to a set of acceptable labels. • Explicit label control • Ingress LSR may specify the label(s) to use on one, some or all of the explicitly routed links for the forward and/or reverse path. • Bi-directional symmetric LSP • A symmetric bi-directional LSP has the same traffic engineering requirements including fate sharing, protection and restoration, LSRs, and resource requirements in each direction. • Downstream and upstream data paths are established using a single set of signaling messages. • New Upstream Label Object/TLV • Rapid notification of failure and events • Acceptable Label Set for notification on label error • Expedited notification (RSVP-TE only) • Link protection • Protection Information Object/TLV indicates: • The desired link protection for each link of an LSP • Whether the LSP is a primary or secondary LSP

27. GMPLS – LSP Protection and restoration • So far, only intra-area, intra-layer P&R mechanisms for handling single failure scenarios are being discussed. • Protection schemes: • 1+1 link protection • 1:N or M:N link protection • Enhanced protection • 1+1 LSP protection • Restoration schemes: • End-to-end LSP restoration with re-provisioning • End-to-end LSP restoration with pre-signaled recovery bandwidth reservation and no label pre-selection • End-to-end LSP restoration with pre-signaled recovery bandwidth reservation and label pre-selection • Local LSP restoration

28. GMPLS extensions to the MPLS control plane – a summary • Support of devices that perform switching in the time, wavelength and space domain. • Use of label stacking and the resulting LSP interface hierarchy • The concept of link bundling • The new Link Management Protocol (LMP) for automatic link configuration and control • Computation of physically disjoint paths by use of Shared Risk Link Group (SRLG). • The establishment of bi-directional symmetric LSPs

29. PSC Cloud TDM Cloud LSC Cloud LSC Cloud TDM Cloud PSC Cloud FSC Cloud Fiber 1 Bundle Fiber n PSC TDM LSC Explicit Label LSPs Time-slot LSPs Time-slot LSPs Explicit Label LSPs l LSPs l LSPs Fiber LSPs (multiplex low-order LSPs) (demultiplex low-order LSPs) GMPLS - LSP hierarchy • Nesting LSPs enhances system scalability • LSPs always start and terminate on similar interface types • LSP interface hierarchy • Packet Switch Capable (PSC) Lowest • Layer 2 Switch Capable (L2SC) • Time Division Multiplexing Capable (TDM) • Lambda Switch Capable (LSC) • Fiber Switch Capable (FSC) Highest

30. Bundled Link 1 Bundled Link 2 GMPLS - Link Bundling • Allows multiple parallel links between nodes to be advertised as a single link into the IGP • Enhances IGP and traffic engineering scalability • Component links must have the same: • Link type • Traffic engineering metric • Set of resource classes (colors) • Link multiplex capability (packet, TDM, λ, port) • (Max bandwidth request)  (bandwidth of a component link) • Admission control is applied on a per-component link basis

31. GMPLS references • Optical Network Service Requirements, Internet Draft <draft-ietf-ipo-carrier-requirements-05>, December 2002 • Generalized Multi-Protocol Label Switching (GMPLS) Architecture, RFC 3945, October 2004 • Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description, RFC 3471, January 2003 • Routing extensions in support of generalized MPLS, RFC 4202, October 2005 • LSP hierarchy with generalized MPLS TE, RFC 4206, October 2005 • Requirements for Generalized MPLS (GMPLS) Signaling Usage and Extensions for Automatically Switched Optical Network (ASON), RFC 4139, July 2005 • Requirements for Generalized MPLS (GMPLS) Routing for Automatically Switched Optical Network (ASON), RFC 4258, November 2005

32. GMPLS references cont. • OSPF extensions in support of generalized MPLS, RFC 4203, October 2005 • IS-IS extensions in support of generalized MPLS, RFC 4205, October 2005 • Generalized Multi-Protocol Label Switching (GMPLS) signaling – Constraint-based routed label distribution protocol (CR-LDP) extensions, RFC 3472, January 2003 • Generalized Multi-Protocol Label Switching (GMPLS) signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) extensions, RFC 3473, January 2003 • Link management protocol (LMP), RFC 4204, October 2005 • Impairments and other constraints on optical layer routing, RFC 4054, May 2005 • Shared risk link groups inference and processing, Internet Draft <draft-papadimitriou-ccamp-srlg-processing-02>, June 2003

33. GMPLS technology specific references • Framework for GMPLS-based control of SDH/SONET networks, RFC 4257, December 2005 • Generalized Multi-Protocol Label Switching (GMPLS) Extensions for Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH) Control, RFC 3946, October 2004 • Generalized MPLS (GMPLS) signaling extensions for G.709 optical transport networks control, RFC 4328, January 2006 • Traffic engineering extensions to OSPF for Generalized MPLS control of Sonet/SDH networks, Internet Draft <draft-mannie-ccamp-gmpls-sonet-sdh-ospf-01>, February 2003 • Traffic engineering extensions to OSPF for Generalized MPLS control of G.709 optical transport networks, Internet Draft <draft-gasparini-ccamp-gmpls-g709-ospf-00>, November 2002

34. ITU-T Recommendations • G.8080 Architecture for the Automatic Switched Optical Network (ASON) (06/2006) • G.7712 Architecture and Specification of Data Communication Network (03/2003) • G.7713 Distributed Call and Connection Management (DCM) (05/2006) • G.7713.1 Distributed call and connection management (DCM) based on PNNI (03/2003) • G.7713.2 Distributed Call and Connection Management: Signaling mechanism using GMPLS RSVP-TE (03/2003) • G.7713.3 Distributed Call and Connection Management: Signaling mechanism using GMPLS CR-LDP (03/2003) • G.7714 Generalized automatic discovery for transport entities (08/2005) • G.7715 Architecture and Requirements for Routing in the Automatic Switched Optical Networks (06/2002) • G.7715.1 ASON routing architecture and requirements for link state protocols (02/2004)

35. Optical Internetworking Forum (OIF) Implementation agreements • User Network Interface (UNI) 1.0 Signaling Specification, October 2001 • User Network Interface (UNI) 1.0 Signaling Specification, Release 2: Common Part, February 2004 • RSVP Extensions for User Network Interface (UNI) 1.0 Signaling, Release 2, February 2004 • Intra-carrier E-NNI Signaling Specification, February 2004

36. Transport-MPLS (T-MPLS) • Standardized by ITU-T for application in transport part of network only. • Simplified MPLS: all features not necessary for connection-oriented applications are removed, i.e. less complex operation and more easily managed than MPLS. • Management principles are adopted from existing standards/practice, e.g. from SONET/SDH. • Supports - engineered point-to-point bi-directional LSPs, - end-to-end LSP protection, and - advanced OAM. • Goal is to provide reliable packet-based technology (MPLS) in a form that is aligned with circuit-based transport networking.

37. T-MPLS (2) Differences from MPLS: • Use of bi-directional LSPs traversing the same links and nodes. • No LSP merging option. (Multipoint-to-point is allowed in MPLS, as in IP). Not allowed in pure connection oriented network. • No Equal Cost Multiple Path (ECMP) option. Not needed in connection-oriented network. • No Penultimate Hop Popping (PHP) option. Label must be present in last node. • (See whitepaper by TPACK: ”Transport-MPLS A New Route to Carrier Ethernet” for overview – or standards).