Multiprotocol Label Switching

1. Multiprotocol Label Switching Uniting Routing and Switching for Scalable, High Performance Services Part #

2. Agenda • Layering • Internet Core Switching/Routing • Motivations for MPLS • MPLS Overview • MPLS Applications • Summary Part #

3. LAYER ROLE * Functionality: + Implement the desired procedure. + Provide the user interface 7. Application 6. Presentation 5. Session * Provide enhanced services 4. Transport * Provide app to app link 3. Network * Provide host to host link 2. Data Link * Provide physical connection to the net 1. Physical * Provide physical connection to the net OSI Reference Model

4. TCP/IP Reference Model OSI TCP/IP Application 7. Application 6. Presentation Not Present 5. Session Not Present 4. Transport Transport 3. Internet 3. Network 2. Data Link 2. Data Link 1. Physical 1. Physical

5. FTP client FTP server TCP TCP TCP/IP Architecture Terms Host A Host B Router IP (L3) IP(L3) IP ehr drv atm drv ATM (L2) Ethernet (L2)

6. Service Provider Backbone Remote Office Main Office POP CORE (ATM) POP Remote Office POP Service Provider POP = Point of Presence

7. mesh of interconnected routers the fundamental question: how is data transferred through net? circuit switching: dedicated circuit per call: telephone net example: ATM packet-switching: data sent thru net in discrete “chunks” The Network Core

8. End-end resources reserved for “call” link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required Network Core: Circuit Switching

9. each end-end data stream divided into packets user A, B packets share network resources each packet uses full link bandwidth resources used as needed, Network Core: Packet Switching resource contention: • aggregate resource demand can exceed amount available • congestion: packets queue, wait for link use • store and forward: packets move one hop at a time • transmit over link • wait turn at next link

10. Goal: move packets among routers from source to destination through high speed switching core datagram network: destination address determines next hop routes may change during session analogy: driving, asking directions virtual circuit network: each packet carries tag (virtual circuit ID), tag determines next hop fixed path determined at call setup time, remains fixed thru call Example Application IP/ATM Packet-switched networks Over Circuit-switched networks

11. ROUTE AT EDGE, SWITCH IN CORE CORE (ATM) POP POP IP #L2 IP #L2 IP #L2 IP IP IP Routing In the Edge IP Routing In the Edge LABEL SWITCHING In the Core

12. Scalability. Need full (n^2) mesh of virtual-circuits for desired performance, or partial meshing for low cost. IP uses any size packets whereas ATM uses 53 Byte-cells. More bandwidth not efficient and very expensive Geographically dispersed enterprise networks need to be connected for transparent and secure private IP interconnection. IP and circuit-switching (e.g., ATM) technology uses different addressing scheme Addition/deletion of new branch office is an administrative nightmare: ‘n’ virtual circuits need to added/deleted Each edge router has to be big, fat, and tunnel rich. What is the Problem with Current Packet-Switching/Circuit-Switching or IP/ATM?

13. IP/ATM Topology

14. Solution: MPLS • Integrate best of Layer 2 and Layer 3 • Scalability • Reduce operations costs • Increase reliability • Create new revenue from value added IP Services. • Virtual Private Networks(VPN) • Traffic Engineering

15. RSVP IP Multicast IP CoS Key MPLS Capabilities IP/ATM Integration Traffic Engineering VPN’s

16. MPLS Topology

17. What is MPLS? • It is simply a Layer 2 tunnel designed to interoperate with ANY layer 3 protocol, especially IP. • Analogous to an ATM or Frame Relay PVC • Low-overhead virtual circuits for IP • IP packets are encapsulated in the ingress switch known as the Label Edge Router (LER) • Labels change at each segment in a Label Switched Path (LSP) • Label Switched Router (LSR) swaps incoming label with new outgoing label • Labels have “local significance”

18. MPLS Header • IP packet is encapsulated in MPLS header and sent down LSP • IP packet is restored at end of LSP by egress router • TTL is adjusted also … IP Packet 32-bit MPLS Header

19. MPLS Header • Label • Class of service • Stacking bit • Time to live • Decrement at each LSR, or • Pass through unchanged Label CoS S TTL

20. MPLS Operation 1a. Existing routing protocols (e.g. OSPF, ISIS) establish reachability to destination networks 4. Label Edge Router at egress removes label and delivers packet 1b. Label Distribution Protocol (LDP) establishes label to destination network mappings. 2. Ingress Label Edge Router receives packet, performs Layer 3 value-added services, and “label” packets 3. Label Switches switch label packets using label swapping

21. How Does It Work? • Four fundamental components • Packet Forwarding • Path signaling • Path selection • Mapping Forwarding Equivalence Class

22. IP 47.1.1.1 Traditional IP Forwarding 47.1 1 IP 47.1.1.1 2 IP 47.1.1.1 1 3 2 IP 47.1.1.1 1 47.2 3 47.3 2

23. IP 47.1.1.1 IP 47.1.1.1 MPLS IP forwarding via Label Switched Path (LSP) 1 47.1 3 3 2 1 1 2 47.3 3 47.2 2

24. PATH PATH PATH Label Switch Path Signaling Seattle Boston (Egress) San Francisco (Ingress) Miami

25. RESV RESV RESV Label Switched Path Signaling • Once path is established, signaling protocol assigns label numbers in reverse order from Boston to San Francisco • Signaling protocol sets up path from San Francisco to Boston, reserving bandwidth along the way Seattle Boston (Egress) 0 1965 San Francisco (Ingress) 1026 Miami

26. IP 47.1.1.1 IP 47.1.1.1 Path SelectionExplicitly Routed LSP ER-LSP 1 47.1 3 3 2 1 1 2 47.3 3 47.2 2

27. MPLS Benefits Benefits of MPLS • Shared backbone for economies of scale • Keep up with Internet growth • Reduced complexity for lower operational cost • Faster time to market for IP services => more revenue IP over ATM Integration • Traffic eng. for lower trunk costs; • Hierarchical routing for improve reliability of core • Shared IP/Frame backbone for economies of scale Traffic Engineering • New revenue opportunity for SPs • Scalability for lower operational costs and faster rollout • L2 privacy and performance for IP VPNs 14

28. IP over ATM Integration IP over ATM VCs IP over MPLS • ATM cloud invisible to Layer 3 Routing • Full mesh of VCs within ATM cloud • Many adjacencies between edge routers • Topology change generates many route updates • Routing algorithm made more complex • ATM network visible to Layer 3 Routing • Singe adjacency possible with edge router • Hierarchical network design possible • Reduces route update traffic and power needed to process them MPLS eliminates the “n-squared” problem of IP over ATM VCs

29. Traffic Engineering Example BEFORE Utilization increases by 10% 100Mbps@100% 100Mbps @90% SELECTED PATH BY TE 100Mbps @60 100Mbps@70% OSPF 25Mbps @ 30% 25Mbps @ 70% D 100Mbps @ 50% TE S

30. Virtual Private Networks 1 Physical Network == Many Private Networks The Physical Network Topology PHYSICAL LOGICAL R R R R R R R R R R R R R R R R R VPN 1 VPN 4 VPN 2 VPN 3

31. VPN Example Private View Public View Private View Cust A 10.1.1 VPN 1 Controlled Route Distribution Cust A 10.2.1 VPN 1 (15)10.1.1 (15)10.2.1 (15)10.3.1 Internet- Scale VPN Cust A 10.3.1 VPN 1 (354)128.24.2 (354)128.24.1 Cust B 128.24.2 VPN 2 Forwarding Examples IN OUT (1)10.2.1 (1)10.1.1 (1)10.3.1 (2)128.24.2 (2)128.24.1 Cust B 128.24.1 VPN 2

32. 10.150.25.1 Parts DB Customer BSan Jose 10.150.25/24 Customer ABoston VPN B 10.150/16 VR Vendors Extranet Internet VR 10.151/16 VR Customer ANYC VR 10.150.5/24 VR Customer BNYC 10.152/16 VPN A Customer AWash. DC Separate Route Tables and Private Addressing MPLS

33. Summary • MPLS Label provides: • Scalable IP routing • Advanced IP services • Internet scale VPNs • MPLS Benefits: • Lower operations costs • Keep up with Internet growth • New revenue services • Faster time to market MPLS IP

34. Questions?

35. Thank You Luis Marrero lmarrero@ccs.neu.edu