MPLS is the enabling technology for the New Broadband (IP) Public Network

Transcription

1 From the MPLS Forum Multi-Protocol Switching (MPLS) An Overview Mario BALI Turin Polytechnic MPLS is the enabling technology for the New Broadband (IP) Public Network MPLSoverview_en - M. Baldi: see page MPLSoverview_en - 5 M. Baldi: see page The Onion that Makes Providers Cry ATM Circuit Emulation IP over Frame Relay IP over ATM IP IP ATM IP over SONET/SH Leased Line WM ATM Frame Relay IP IP over ATM Circuit Emulation IP over WM The Future: WM, IP, MPLS IP router with LAN or WAN interface IP λ Switching IP/MPLS IP router with T3 interface PABX with T interface IP router with LAN (GE) or WAN (PoS) Interface MPLSoverview_en - 6 M. Baldi: see page MPLSoverview_en - 7 M. Baldi: see page

2 The Underlying Idea Route packets based on a label As opposed to routing based on IP address Why? Faster table lookup Indexed access vs. longest prefix matching Traffic engineering capabilities How? Stay tuned IP IP Packet Packet MPLS History Tag Switching IP over ATM No need for address translation mechanisms Simplified signaling Single control plane ATM with IP Reuse of ATM switching hardware G-MPLS (Generalized MPLS) Unifying control plane Circuit switching: SONET/SH Lambda Switching MPLSoverview_en - 8 M. Baldi: see page MPLSoverview_en - 33 M. Baldi: see page MPLS Technology Switch (LSR): or switch that handles MPLS and IP (LER): LSR at the edge of an MPLS network Ingress LERs are responsible for classifying unlabelled IP packets and appending the appropriate label. Egress LERs are responsible for removing the label and forwarding the unlabelled IP packet towards its destination. Forwarding Equivalence Class (FEC): IP packets that follow the same path through the MPLS network receive the same treatment at each LSR MPLS network or MPLS cloud Network Architecture Switch Switch Switch Switch Switch Switch MPLSoverview_en - 9 M. Baldi: see page MPLSoverview_en - M. Baldi: see page

3 Ingress LSR MPLS network or MPLS cloud Switched Path (LSP) Egress LSR Ingress LSR MPLS network or MPLS cloud Switched Path (LSP) A X In 4 Out 3 3 In In Out Out Egress LSR 3 In Out MPLSoverview_en - M. Baldi: see page MPLSoverview_en - M. Baldi: see page MPLS Key Elements MPLS header Contains the MPLS label based on which LSRs forward the packet Headers can be stacked: label stack Enhanced IP routing protocols istribute topology and constraint based data distribution protocols (LPs) Connection establishment (signaling) protocols LSRs set up a complete Switched Path (LSP) from ingress LSR to egress LSR MPLS adds a connection oriented paradigm to IP networks MPLS Shim Header Structure Layer Header 4 Octets Exp. S TTL Switching Look up inbound label + port (+Exp) to determine outbound label + port + treatment MPLS "shim" headers... IP Packet : -bit value, (-6 reserved) Exp.: 3-bits Experimental ( ToS) S: -bit Bottom of stack TTL: 8-bits Time To Live Header operations Swap (label) Push (a new header) Pop (a header from stack) MPLS encapsulations are also defined for ATM and Frame relay. MPLSoverview_en - 3 M. Baldi: see page MPLSoverview_en - 4 M. Baldi: see page

4 Establishing label bindings The downstream end of a link needs to know what label values will be received By management action equivalent to ATM PVCs Not scalable No interoperability between management systems multi-operator connections difficult if not impossible Protocol (IP) driven service establishment End points and/or routes trigger LSP setup and tear down Automatic LSP establishment process distribution protocol MPLSoverview_en - 5 M. Baldi: see page MPLS Routing protocols Start with existing IGP s istribute OSPF topology IS-IS information only BGP-4 Enhance to carry constraint data OSPF-TE Constraint IS-IS TE data Link capacity Constraint based Link utilization routing is is the key Resource class to to Traffic Priority Engineering Pre-emption MPLSoverview_en - 6 M. Baldi: see page istribution Protocols LP RSVP CR-LP RSVP-TE Hop by by Hop routing Ensures routers agree on on bindings between FEC s and the the labels. paths follow same route as as conventional routed path Explicit constraint based routing Route determined by by ingress LSR based on on overall view of of topology, and constraints Traffic engineering CoS and (QoS) Fast (5ms) rerouting MPLS Partitions Routing and Forwarding Routing Forwarding OSPF, IS-IS, BGP, RIP MPLS Forwarding Table More flexibility to develop new routing solutions without impacting the data plane hardware of label switch routers Single forwarding paradigm multiple routing paradigms Classful Addr. Prefix? Classless Addr. Prefix? Multicast Addr.? Port No.? ToS Field? Exact Match on Fixed Length The edge LSR uses a wide variety of parameters in determining the FEC, and not just the destination IP address Flexibility in forming FEC s MPLSoverview_en - 7 M. Baldi: see page MPLSoverview_en - 8 M. Baldi: see page

5 Applications of MPLS Traffic Engineering Adding Class of Service (CoS) and Quality of Service (QoS) Network scalability Supporting IP VPN s Traffic Engineering Current IGPs lead to Hyper- Aggregation... TRAFFIC FOR SHORTEST PATH ROUTE S CONGESTION MASSIVE CONGESTION MPLSoverview_en - 9 M. Baldi: see page MPLSoverview_en - M. Baldi: see page Traffic Engineering Traffic Engineering is the Answer S resulting in congestion and underutilization TRAFFIC FOR SHORTEST PATH ROUTE 9 UNER ULTILIZE] LINKS 4 OVERUTILIZE ] Objectives Map actual traffic efficiently to available resources Controlled use of resources Redistribute traffic rapidly and effectively in response to changes in network topology Particularly as a consequence of line or equipment failure protection This complements Network Engineering Putting network capacity where traffic is CONGESTION MASSIVE CONGESTION MPLSoverview_en - M. Baldi: see page MPLSoverview_en - M. Baldi: see page

6 S Traffic engineering distributes traffic Congestion and underutilization eliminated Benefit of MPLS traffic engineering ATM used for Traffic engineering in large IP networks Two control planes s are ATM unaware Large number of routing adjacencies Limited scalability MPLS is is IP aware Single IP IP control plane matching the physical topology: it it scales better and it it is is simpler Extended into MPλS (MPLambdaS): MPLS Traffic Engineering technology to Optical networking MPLSoverview_en - 3 M. Baldi: see page MPLSoverview_en - 4 M. Baldi: see page Adding CoS and QoS Explicit path set up can also associate specific resource requests with an FEC Class of service Establish relative priority of one FEC over another No absolute guarantees Quality of service Specific guarantees on Bandwidth elay Burst size etc Support the iff-serv QoS model EF, AF, etc. MPLSoverview_en - 5 M. Baldi: see page CoS CoS and and QoS QoS require explicit support in in the the data data and and control plane of of the the LSR s S-aware (per-class) Traffic Engineering Benefits of MPLS QoS Unified or converged network supporting all classes of service The IP Qos model for supporting real time services such as voice is at an early stage. Most multi-service networks are moving to a Ships-in-the-night paradigm ATM services with ATM protocols MPLS control plane for IP services MPLSoverview_en - 6 M. Baldi: see page

7 Hierarchy via Stack Network scalability Within each domain the IGP simply needs to allow the Border (ingress) routers to determine the appropriate egress boarder router This drastically reduces size of routing tables in transit routers Layer Header 3 IP Packet MPLS omain MPLS omain MPLS omain 3 Benefit of MPLS in scaling MPLS labels introduce hierarchy Transit routers no longer need to handle complete routing tables New layers of the hierarchy can be introduced as needed for scaling. Exact matching of label much easier and faster than longest prefix matching MPLSoverview_en - 7 M. Baldi: see page MPLSoverview_en - 8 M. Baldi: see page Support of IP VPNs A Virtual Private Network An IP network delivering private network services over a public infrastructure Supports global and non-unique private address space Supports CoS and QoS Use of labels isolates IP addresses within public network from customer IP addresses MPLS enables highly scalable VPNs Not currently standardized by IETF No RFC has been issued yet Benefit of MPLS IP VPNs Mechanism to scale Number of VPNs Number of members per VPN Other approaches require tunnels to be explicitly (manually) setup between each pair of VPN sites Allows VPNs to have non-unique IP addressing Great flexibility in defining VPN services From the mapping to FECs CoS and QoS Service Level Agreements (SLA s) can be associated with a VPN MPLSoverview_en - 9 M. Baldi: see page MPLSoverview_en - 3 M. Baldi: see page

8 MPLS Status MPLS is a critical additional capability for IP networks. It solves problems for which no other solutions are known. It is difficult to anticipate the longer term future and what applications may be supported because of the innovations MPLS enables. MPLS introduces a significant architectural change in IP networks. It is the future of the converged IP network Players in the MPLS Arena IETF - Internet Engineering Task Force MPLS working group PPVPN (Provider Provisioned VPN) working group MPLS Forum Consortium of MPLS switch vendor Goal: speed up deployment of MPLS Tackles issues not addressed by IETF E.g., applications, VoMPLS, MPLS based ASL MPLSoverview_en - 3 M. Baldi: see page MPLSoverview_en - 3 M. Baldi: see page