1. © 2000, Cisco Systems, Inc. 2-1 Chapter 2 MPLS Background and Concepts

2. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-2 Objectives Upon completion of this chapter, you will be able to perform the following tasks: Place MPLS technology within the network Identify practical applications for MPLS technology Provide a high-level description of MPLS technology Identify Services provided by MPLS technology Explain the features and benefits of MPLS technology

3. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-3 Agenda MPLS Technology Overview MPLS Terminology Market Drivers for MPLS Services Provided by MPLS Technology Label Forwarding Concepts Types of MPLS Networks ATM MPLS

4. © 2000, Cisco Systems, Inc. www.cisco.com 2-4 Driving Business Forces from Old World to New

5. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-5 Customer Perspective Current Requirements Quality of Service (QoS) Privacy Availability Reliability New Requirements Multiple service classes Multiple service options –ATM, FR, Private IP, Public IP –Multiple VPN options Lower cost managed services Any-to-any connectivity Extranets, COINS Seamless integration IP/VPN SLA requirements cannot be met with today’s technology! IP/VPN SLA requirements cannot be met with today’s technology!

6. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-6 Customer Vendor Preferences Customer Vendor Preferences Source: Business Communications Review Customer Networking Staffing Needs Source: CIMI Corp. Demand: low cost, managed IP services from one vendor

7. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-7 Value-Added IP Services Problem: and How to Build a Network that Can Deliver these Services and SLAs Problem: and How to Build a Network that Can Deliver these Services and SLAs Service Provider Perspective Growth: Private IP, Public IP Multimedia Service Portfolio Revenue: Frame Relay, ATM, Managed Services Managed Intranets Managed Intranets Private Voice Networks Content Hosting

8. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-8 The Problem We can’t get there from here using traditional technologies: ATM or Frame Relay virtual circuits IP tunneling Encryption Network address translation Why? Functionality tradeoffs Complexity Cost Service degradation

9. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-9 The Solution: MPLS A new paradigm that delivers the best of both worlds: –Privacy and Quality of Service (QoS) of ATM and Frame Relay –Flexibility and scalability of IP Foundation for IP business services Flexible grouping of users and value-added services Low-cost managed IP services Scalability: small to large private networks

10. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-10 MPLS: The First Complete IP Solution Any-to-Any Connectivity Leased Lines Frame Relay/ ATM IPMPLS User N2 (logical) NN Network N2 (logical) NN QoS Privacy Low Cost Managed Services MPLS is the first solution that delivers on all the requirements for new world private IP networks.

11. © 2000, Cisco Systems, Inc. www.cisco.com 2-11 MPLS Technology Overview

12. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-12 MPLS Basics Definition –Multiprotocol Label Switching –Emerging IETF industry Standard –Based on Cisco’s Label Switching submission Mechanics –Forwards packets based on labels –Packets are switched not routed

13. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-13 MPLS Basics (cont.) Blends layer-three routing with label swapping and forwarding –Simplicity of layer-two forwarding offers high performance –Layer-three routing has proven scalability –Separation of forwarding and routing aids evolution of routing

14. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-14 MPLS Basics (cont.) Simplifies integration of ATM and IP –Enables IP forwarding at ATM rates –Scalably integrates IP with ATM switches Enables Traffic Engineering Improves router scalability Hierarchical routing/forwarding Moderates router forwarding improvement

15. © 2000, Cisco Systems, Inc. www.cisco.com 2-15 MPLS Terminology

16. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-16 MPLS Terminology Cisco Express Forwarding (CEF) Customer Edge (CE) Router A router that is part of a customer network and interfaces to a provider edge (PE) router Edge Label Switch Router (Edge LSR) The edge device that performs initial packet processing and classification. It applies the first label. This device can be either a router such as the Cisco 7500 or a switch with built-in routing such as the Cisco MGX 8800.

17. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-17 MPLS Terminology (cont.) Label A constant-width Label that selects how to forward a packet Label Imposition The act of putting the first label on a packet

18. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-18 MPLS Terminology (cont.) Label Distribution Protocol (LDP) Communicates labels and their meaning among Label Switch Routers (LSRs). It assigns labels in edge and core devices to establish Label Switch Paths (LSPs) in conjunction with routing protocols such as Open Shortest Path First (OSPF), Intermediate System to Intermediate System (IS-IS), Routing Information Protocol (RIP), Enhanced Interior Gateway Routing Protocol (EIGRP) or Border Gateway Protocol (BGP).

19. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-19 MPLS Terminology (cont.) LIB Label Information Base LFIB Label Forwarding Information Base

20. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-20 MPLS Terminology (cont.) Label Switch Controller (LSC) An MPLS router that controls the operation of a separate ATM switch in such a way that the two function together as a single ATM Label Switch Router

21. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-21 MPLS Terminology (cont.) Label Switched Path (LSP) Path defined by all labels assigned between end points. An LSP can be dynamic or static. Dynamic LSPs are provisioned automatically using routing information. Static LSPs are explicitly provisioned.

22. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-22 MPLS Terminology (cont.) Label Switch Router (LSR) A core device that switches labeled packets according to precomputed switching tables. This device can be a switch or a router. Label Virtual Circuit (LVC) A hop-by-hop connection established at the ATM transport layer to implement an LSP. Unlike ATM VCs, LVCs are not implemented end-to-end and do not result in wasted bandwidth.

23. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-23 MPLS Terminology (cont.) Provider Edge Router (PE) A router that is part of a service provider’s network that interfaces to a Customer Edge (CE) Router SLA Service Level Agreement

24. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-24 MPLS Terminology (cont.) Virtual Switch Interface (VSI) A protocol that runs between a slave and a master. It enables a LSC to control an ATM switch over an ATM link.l It has recently been submitted to the Multi-Service Switching Forum as an open standard.

25. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-25 MPLS Terminology (cont.) VPN Routing/Forwarding Instance (VRF) –Consists of an IP routing table, a derived forwarding table, and a set of rules and routing protocols that determine the content of the forwarding table –Generally, a set of routing information that defines a customer VPN site that is attached to a PE router

26. © 2000, Cisco Systems, Inc. www.cisco.com 2-26 MPLS Operation

27. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-27 MPLS Operation

28. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-28 MPLS Operation Step 1 1. Existing routing protocols (e.g. OSPF, IS-IS) establish reachability to destination networks

29. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-29 MPLS Operation Step 2 1. Existing routing protocols (e.g. OSPF, IS-IS) establish reachability to destination networks 2. Label Distribution Protocol (LDP) establishes label to destination network mappings.

30. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-30 MPLS Operation Step 3 1. Existing routing protocols (e.g. OSPF, IS-IS) establish reachability to destination networks 2. Label Distribution Protocol (LDP) establishes label to destination network mappings 3. Ingress Edge LSR receives packet, performs Layer 3 value-added services, and “labels” packets

31. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-31 MPLS Operation Step 4 1. Existing routing protocols (e.g. OSPF, IS-IS) establish reachability to destination networks 2. Label Distribution Protocol (LDP) establishes label to destination network mappings 3. Ingress Edge LSR receives packet, performs Layer 3 value-added services, and “labels” packets 4. LSR switches packets using label swapping

32. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-32 MPLS Operation Step 5 5. Edge LSR at egress removes label and delivers packet 1. Existing routing protocols (e.g. OSPF, IS-IS) establish reachability to destination networks 2. Label Distribution Protocol (LDP) establishes label to destination network mappings 3. Ingress Edge LSR receives packet, performs Layer 3 value-added services, and “labels” packets 4. LSR switches packets using label swapping

33. © 2000, Cisco Systems, Inc. www.cisco.com 2-33 Services Provided by MPLS

34. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-34 A Foundation for Value Added IP Services Multiservice ATM switch or Gigabit router backbone Services and Applications VPN-Aware Networks Content VoIP Hosting Net Commerce ExtranetInternet MPLS enabled Infrastructure Infrastructure Multimedia Training Frame Relay ATM MPLS-EnabledIPNetwork Intranet A

35. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-35 Provider MPLS Network MPLS Labels: Routes and Service Attributes Labels are the key Labels are the key: router/switch interoperability pre-configured service attributes Single memory access to determine all services to apply ATM Switch Router Service Class (CoS) Privacy (VPN) Traffic Engineered Path Label IP Packet

36. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-36 Delivering CoS for Business Services Video Conferencing Mission-critical Applications Email, Web browsing, Pointcast CoS Policy: traffic classification and bandwidth management application-based per-customer Multiple labels per destination: distinct service classes layer 3 routing: no end-to-end VCs layer 3 traffic engineering per-flow consistency MPLS ATM Network Policy Database IP precedence to label mapping

37. © 2000, Cisco Systems, Inc. www.cisco.com 2-37 Label Forwarding Concepts

38. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-38 Label Switching Basics: Summary Label Switching puts IP routing functions on ATM switches. This provides better IP and ATM integration and better scaling. On non-ATM equipment, Label Switching simplifies the forwarding operation and introduces ‘lightweight virtual circuits’. This allows advanced features like Label Switching Traffic Engineering.

39. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-39 Label Switching: Forwarding A pair of routers handle a class of packets with similar parameters The first router classifies the packets….. summarizes its decision with a label on the packet. The next router just looks at the label Label switching simplifies forwarding, pushes packet classification back towards the edge

40. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-40 Forwarding Component Label Forwarding Information Base (LFIB) Indexed by incoming label Entries consist of one or more subentries: — Outgoing label — Outgoing interface — Outgoing MAC address LFIB is per box (replicated on VIP cards)

41. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-41 Forwarding Component (cont.) IOS Label Forwarding Code is based on Cisco Express Forwarding (CEF) –Maintenance of label rewrite structures in LFIB –Recursive route resolution –IP to label switching (label imposition) path

42. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-42 Forwarding Component (cont.) Label Forwarding Procedure: Forwarding Algorithm: –Extract label from packet –Find LFIB entry for incoming Label –Possible operations: Replace label in packet with outgoing label(s) Remove a label from the packet Send packet on outgoing interface Forwarding Algorithm is Network- layer Independent Forwarding Algorithm is Network- layer Independent

43. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-43 Label Switching Control Plane FIB: for unLabelged packets New function: outgoing Labeled packet TFIB: for incoming Labeled packets   R1  R2  FIB  UnLabeled packet  Labeled packet  TFIB  UnLabeled packet  Labeled packet  UnLabeled packet  Labeled packet

44. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-44 TIB and TFIB TIB is populated by TDP TFIB is derived from TIB and used for packet forwarding  Destination Incoming Label (Peer, Outgoing Label)  D tR1 (R2:0,tR2)  Label Information Base (TIB)  Incoming Label Outgoing Label Interface  tR1 tR2 i3  Label Forwarding Information Base (TFIB)

45. © 2000, Cisco Systems, Inc. www.cisco.com 2-45 Types of MPLS Networks

46. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-46 Dynamic MPLS Labels allocated and distributed based on routing topology LDP used for label distribution LDP run in parallel with routing protocols Other label distribution mechanisms possible –BGP –PIM

47. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-47 Static Path MPLS Label allocated based on a configured path Also known as Label Switched Path (LSP) tunnels RSVP extensions used to select path and return labels First application is Traffic Engineering

48. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-48 MPLS Applications Hierarchical Routing and Forwarding Traffic Engineering

49. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-49 Hierarchical Routing Conventional Approach Border Routers Run BGP with External Peers Interior Routers All Routers Run IBGP to Learn Exterior Routing Information, and IGP for Interior Topology

50. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-50 Hierarchy of Routing Knowledge Isolate inter-domain and intra-domain routing Improved stability Reduce interior router table size Only IGP routes stored at interior nodes Improve BGP scaling Only border nodes need run BGP

51. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-51 Interior Routers Hierarchy of Routing Example Border Router Applies Label to Reach BGP Next Hop LabelAddr Interior Routers Run IGP Only Label Addr

52. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-52 Two Level Dynamic Labels Border router Interior routers AddrBlg Ilg AddrBlgIlg AddrBlgIlg Addr Blg AddrBlgIlg Key IGP Label BGP Label IGP Label BGP Label Key Blg Ilg Blg

53. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-53 Traffic Engineering Example Default L3 path TE path Dest. AS

54. © 2000, Cisco Systems, Inc. www.cisco.com 2-54 ATM MPLS

55. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-55 MPLS and ATM Label Switching Steps: –Make forwarding decision using fixed-length Label (64 bits) –Rewrite label with new value Similar to ATM cell switching Key differences: –Label set up: LDP vs ATM Forum Signaling –Label granularity: Per-prefix

56. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-56 ATM Label Switching VPI/VCI field is used as a ‘Label’ Label is applied to each cell, not whole packet Label swapping = ATM switching

57. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-57 Label Distribution for ATM Uses LDP in “Downstream on Demand” mode To route a label ATM link, Virtual Channel (VC) labels are requested when topology changes Precedence associated with LVC Some LDP extensions for negotiation of ATM specific parameters

58. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-58 Summary After completion of this chapter, you learned to perform the following tasks: Place MPLS technology within the network Identify practical applications for MPLS technology Provide a high-level description of MPLS technology Identify Services provided by MPLS technology Explain the features and benefits of MPLS technology

59. © 2000, Cisco Systems, Inc. www.cisco.com CMPLS 1.0—2-59 Review Questions