ENTERPRISE MPLS. Kireeti Kompella

Transcription

1 ENTERPRISE MPLS Kireeti Kompella

2 AGENDA The New VLAN Protocol Suite Signaling Labels Hierarchy Signaling Advanced Topics Layer 2 or Layer 3? Resilience and End-to-end Service Restoration Multicast ECMP and Entropy Labels The New VLAN 2 Copyright 2012 Juniper Networks, Inc.

3 WHY ARE YOU HERE? A) because it would have been your turn to cook dinner B) because someone mentioned drinks C) because you needed an alibi D) because you were told that MPLS stood for More Partying, Less Studying E) because networking is cool 3 Copyright 2012 Juniper Networks, Inc.

4 MPLS THE NEW VLAN MPLS is a very flexible forwarding paradigm MPLS can be used for: 1. Faster forwarding (IP forwarding was believed to be too slow!) 2. Traffic engineering 3. Fast recovery from network failures 4. Uniformly transporting a number of link layer technologies 5. Scaling a network: backbone, edge, access 6. Providing VPN services Which of these do you think attracted attention when MPLS first came out? Which spurred the first big deployment? Network virtualization segmentation and isolation Just what VLANs do, but in a manner that is a whole lot more scalable, manageable and adaptable 4 Copyright 2012 Juniper Networks, Inc.

5 WHAT IS MULTI-PROTOCOL LABEL SWITCHING? Forwarding paradigm: what should happen to packets arriving at this box? Control plane: how does this box learn how to deal with packets? The MPLS protocol suite encompasses both forwarding and signaling (control plane). The control plane shares many elements with the IP control plane (hence the term IP/MPLS ) Lesson 1: signaling flow and packet flow are almost always in opposite directions Principle: downstream label allocation 5 Copyright 2012 Juniper Networks, Inc.

6 WHAT IS A LABEL? 20 bits bits Label value TC BoS TTL 32 bits (4 octets) TC = Traffic Class BoS = bottom of stack TTL = time-to-live (as in IP) 6 Copyright 2012 Juniper Networks, Inc.

7 WHAT IS SWITCHING? Most common operation on labels: Label value TC BoS TTL ñ New label value TC BoS TTL-1 Label value gets switched; TC generally stays the same, but may change TTL gets decremented. BoS doesn t change 7 Copyright 2012 Juniper Networks, Inc.

8 WHAT IS MULTI-PROTOCOL? MPLS runs over multiple protocols (Ethernet, PPP, ) MPLS carries multiple protocols (IPv4, IPv6, ) I.e., multi-protocol above and below IPv4, IPv6, Ethernet, ATM, Frame Relay, PPP, TDM! MPLS IPv4, IPv6, Ethernet, ATM, Frame Relay, PPP, TDM 8 Copyright 2012 Juniper Networks, Inc.

9 SIGNALING LABELS To reach FEC F, use label L n To reach FEC F, use label L 1 ingress egress push L n L 3 è L 2 pop L 1 Label Switched Path (LSP) FEC: Forwarding Equivalence Class = set of packets that are to be treated identically from a forwarding point of view All packets in FEC F will be tagged with the same label (L n ) at the ingress, and will follow the same path to the egress Lesson 2: labels are locally significant, and typically downstream-assigned (e.g., egress chooses L 1 ) 9 Copyright 2012 Juniper Networks, Inc.

10 CHARACTERIZATION OF A FEC Typically, the loopback address of a router all packets that will be delivered to their destination via a particular egress router (e.g., BGP next hop) Some signaling protocols allow the creation of multiple LSPs to an egress In this case, the FEC could be further narrowed by QoS class or other contents of a packet This leads to a simple implementation of policy-based routing Determination of a packet s FEC is done only once, at the ingress Intermediate LSRs keep packets in the LSP using the label, swapping it at each hop The egress pops the label and forwards based on IP or other header information 10 Copyright 2012 Juniper Networks, Inc.

11 FORWARDING: VERY MUCH LIKE IP! BGP IGP LDP Prefix BGP NH IGP NH Interface Label /24 Router Y Router X ge-1/1/ /24 Router Q Router P ge-2/2/ Y X Ingress IGP BGP P 11 Copyright 2012 Juniper Networks, Inc. Q

12 APPLICATION: SHOW SOME OF THE BENEFITS OF MPLS Slow IP Local repair Fast MPLS Say link fails 10GE interface GE interfaces Alternate path can be used Say upper link is saturated Lower path has capacity, but is longer (by metric) 12 Copyright 2012 Juniper Networks, Inc.

13 LABEL STACKS AND HIERARCHY One can put multiple labels on a packet. The labels are called a label stack. Label stacks create hierarchy which in turn enables a number of benefits. L2 L1 L3 L2 L1 L2 L1 L3 L2 L2 L1 packet packet packet packet 13 Copyright 2012 Juniper Networks, Inc.

14 SIGNALING Choices for signaling: LDP (hop-by-hop, follows IGP shortest path) Mechanisms exist for multicast, local repair RSVP-TE (hop-by-hop, follows given path) Mechanisms for multicast, local repair, traffic engineering BGP (multi-hop) Used for scaling, and for various VPN technologies 14 Copyright 2012 Juniper Networks, Inc.

15 ADVANCED TOPICS: LAYER 2 OR LAYER 3? Layer 2 easy to understand, configure, manage ( plug-and-play ) fragile: flooding, loops, broadcast storms, VLANs make it not-so-plug-and-play: ACLs, manual policies,... MPLS can give you a Layer 2 look-and-feel with a solid, robust, IP control plane based infrastructure Layer 3 More protocols (more help!) Initial investment higher; payoff greater Robust, scalable, flexible MPLS can add resilience, segmentation, traffic engineering With MPLS, you can choose now, change your mind, migrate to a new approach, adapt, -- it s MULTI-PROTOCOL! 15 Copyright 2012 Juniper Networks, Inc.

16 RESILIENCE AND END-TO-END RESTORATION MPLS Infrastructure End user Dual-homed server complex 16 Copyright 2012 Juniper Networks, Inc.

17 MULTICAST L1 L2 L3 This router must make 3 copies of the incoming packet, put the appropriate label on each, and send each to the next router multiple destinations 17 Copyright 2012 Juniper Networks, Inc.

18 ECMP AND ENTROPY LABELS How about making the ingress do this work, encode it as a label, and allow transit LSRs to simply use that label? L1 L2 L3 L EL packet Stacking is cheap, flexible and effective! single destination This router must choose among 3 next hops in a consistent manner, put the appropriate label on the packet, and send it to the next router How to map a flow consistently to the same link? Typically, by hashing on some header fields 18 Copyright 2012 Juniper Networks, Inc.

19 BACK TO THE NEW VLAN Three different users on three different interfaces Incoming interface VPN Prefix BGP NH VPN Label ge-1/1/1 Engg /24 Router X 22 ge-1/1/2 HR /24 Router Y 33 ge-1/1/3 Finance /24 Router Z 44 Routers in the middle are not aware of the end-to-end VLAN X Y Z BGP 19 Copyright 2012 Juniper Networks, Inc.

20 TYPES OF VPNs Layer 2 and Layer 3 IP VPN RFC 2547/4364 Forward based on IPv4/v6 addresses, but segmented (private) Virtual Private LAN Service (VPLS) RFC 4761/4762 Emulation of an Ethernet segment (really a VLAN!) Ethernet VPNs draft-ietf-l2vpn-evpn Emulation of an Ethernet segment, but with a BGP control plane Scales to very large number of segments, with each segment containing a large number of endpoints Work in progress, both standards and implementation Very similar signaling, forwarding mechanisms, provisioning, management, trouble-shooting, etc. across all of these All can take advantage of ECMP, entropy labels, multicast, 20 Copyright 2012 Juniper Networks, Inc.

21 VPN POLICIES AND MANAGEMENT Overlapping addresses (IP and/or MAC) have been designed in VPN topologies can be very flexible Default is any-to-any Other typical use cases include hub-and-spoke and dual h-and-s VPNs can cross Autonomous System boundaries For example, an internal VPN can connect to a wide-area VPN which in turn connects to a DC VPN in the cloud VPN management is limited to the endpoints; routers in the middle are unaware of the VPNs, and unaffected by VPN scale 21 Copyright 2012 Juniper Networks, Inc.

22 CONCLUSION MPLS is a very flexible, powerful and extensible forwarding paradigm that is accompanied by an equally flexible, powerful and extensible control plane MPLS s starting point (TE) and where it is today (a host of VPN applications) is testament to this MPLS is also by design compatible with IP The MPLS control plane means more to master, but that control plane also significantly reduces provisioning and management MPLS allows a decoupling of transport and services (VPNs) This uses hierarchy in the control plane and label stacking This means that changes can be limited to edge devices This in turn means less disruption to core devices, more stability, MPLS continues to evolve, but much more slowly now 22 Copyright 2012 Juniper Networks, Inc.