Introduction to Multi-Protocol Label

Transcription

1 Introduction to Multi-Protocol Label Switching (MPLS) Matthew Bocci, Alcatel-Lucent IP Division

2 Agenda History of MPLS Standardisation MPLS Architecture Control Plane QoS and Traffic Engineering Protection and Resiliency MPLS Based Services: Layer 3 Virtual Private Networks Layer 2 Virtual Private Networks & Pseudowires

3 IP/MPLS in Carrier Networks >Pt-pt & multicast scalability Multi-segment PWs, Multicast in VPLS / IPVPNs / pt-mp LSPs >Service convergence over MPLS including VPLS >Service enabling the edge L3 based MPLS VPN > Business enabling the core MPLS attempt to enhance network resilience MPLS-enhanced QoS > Infrastructure optimization Traffic engineering Hierarchical core design Development of pseudowires / L2VPNs Unified Control Plane for Non-Packet and Packet Networks Enhanced Network Resilience 1998 Traffic Engineering Virtual Private Networks >Enhance forwarding performance of router networks MPLS Applications Forwarding Performance MPLS Standardisation Activities

4 Multiprotocol Label Switching Architecture MPLS Shim label added to each packet Forwarding decisions are based on label, to follow a label switched path (LSP) Runs over many link layers SDH, Ethernet, etc MPLS Label Edge Router, LER1 Label Switching Router (LSR) Label Edge Router, LER2 LSP LSP IP Packet Label value X added by LER1 X Packet forwarded to LER2 based on Label X Label X swapped with Y Y LER2 pops label & Forwards IP Packet Forwarding Equivalence Class (FEC) e.g. endpoint address 20 Bit label EXP S TTL MPLS Architecture: IETF RFC 3031

5 MPLS Control Plane Distribute FEC/Label bindings between LSRs Label Distribution Protocol (LDP) for non-te LSPs Simple protocol that exchanges label bindings with peer LSRs RSVP-TE for traffic engineered LSPs Soft-state protocol enabling BW parameters & path to be signalled Use label Z to reach FEC X Use label Y to reach FEC X FEC X LER LSR LER

6 QoS and Traffic Engineering MPLS Label: 20 Bit label EXP TTL Encode CoS and/or DP Control plane to determine LSP path and reserve resources along path Label Inferred LSP Drop precedence determined by EXP bits LSRs schedule according to label context Classified according to L2 or L3 criteria Policing/Shaping applied EXP Inferred LSP EXP bits determine CoS / DP LSRs schedule according to EXP bits context RSVP-TE signals resource requirements along LSP path

7 Protection and Resiliency MPLS provides a common protection layer, independent of underlying transport mechanisms Backup LSP Path protection: Protected LSP Demand/2 Load balancing: A B Demand/2 Demand/2 Wide range of options Local protection: Detour A-E Detour B-E A B C D Detour D-E E Detour C-E LSP

8 MPLS based Services and Virtual Private Networks LSP tunnels segregate customer traffic in network Two VPN classes: Layer 3 VPNs: IP Layer 2 VPNs: Virtual Private Wire Service (pt-pt Ethernet, FR, ATM, etc) Virtual Private LAN Service (mp-mp Ethernet) Attachment circuit PSN tunnel Attachment circuit router P routers router router router Service Provider s MPLS network IETF RFC 4664

9 Border Gateway Protocol (BGP) Layer 3 VPNs MP-BGP* exchanges VPN membership/reachability info VRF Customer routes LSP VRF MPLS VRF IP Service *MP-BGP : Multiprotocol BGP Virtual Routing & Forwarding IETF RFC 4364

10 Layer 2 VPNs Pseudowires are building blocks of layer 2 VPNs LDP signalling MPLS Tunnel LSP Layer 2 AC Pseudowire Layer 2 AC Ethernet Frame relay ATM TDM, etc Payload (L2 protocol) PW Label Inner Label LSP Label Outer Label MPLS Label Stack IETF RFC 3985

11 Virtual Private LAN Service (VPLS) Transparent L2 VPN for Ethernet Learns MAC addresses per PW Forwarding based on MAC addresses Split-horizon forwarding for loop prevention Does not use Spanning Tree Uses hierarchy to improve scaling (H-VPLS) MPLS tunnel Ethernet PW Ethernet AC MPLS Network Virtual bridging and forwarding IETF RFC 4762

12 OAM in a Converged MPLS Network OAM tools for each layer of the converged network Bidirectional Forwarding Detection (BFD) Lightweight hello protocol LSP Ping/Trace Modeled after ICMP ping /traceroute AC Pseudowire AC Tunnel LSP Ethernet Frame relay ATM TDM, etc Virtual Circuit Connectivity Verification (VCCV) PW Connectivity verification LDP Status Signalling Defect notifications

13 Summary: Why is MPLS Important? MPLS adds label to a packet to enable it to be switched through a PSN Full set of TE, OAM, and protection mechanisms Enhance to support both Layer 2 and Layer 3 services Core carrier networks moving rapidly to using MPLS Driven by expected lower CAX/OX of a converged network and demands of new servces Ethernet services need MPLS QoS/TE/Protection Enables Ethernet transport layer to support range of legacy (TDM, ATM ) and new services

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