MPLS: The Magic Behind the Myths

1. MPLS: The Magic Behind the Myths Grenville Armitage (author) Scott Crosby (presenter)

2. Problems with IP • No Quality of Service • Necessary for converged network • Realtime voice • Best-effort data • High priority transactions (ATM, control, VC, …) • Performance Scalability • Expensive prefix match for each packet • Traffic Engineering

3. Problems with IP • Tunneling • Tunnel IP over non-IP intermediate • IP over IP over ATM? IP Network IP Network ATM IP Network IP Network

4. Problems with IP • Tunneling • Tunnel IP over non-IP intermediate • Virtual Private Network Duncan EE IP Network Abercr. CS IP Network Abercr. EE IP Network Duncan CS IP Network

5. Problems with IP • Tunneling • Tunnel IP over non-IP intermediate • Virtual Private Network • Traffic Engineering IP Network IP Network IP Network IP Network

6. What is MPLS? • Virtual circuit layer underneath IP • Virtual circuit = virtual wire = label switched path IP Network (Voice) IP Network (ATM) IP Network (Data) MPLS (Virtual Point-to-Point Circuits) Physical Infrastructure (Point-to-Point Circuits)

7. What is MPLS? • Offer service above IP • Converged network • Realtime voice • Best-effort data • High priority transactions (ATM, control …) • On the same physical infrastructure • Hop-by-hop QoS differentiation

8. 5 13 13 13 5 5 Payload Payload Payload Payload Payload Payload How Does MPLS Work? • Packets are tagged and routed based on tags. • All traffic with the same label treated the same IP Routing Layer IP Routing Layer LSR Payload Payload LER LER Payload Payload

9. Other Features of MPLS • Tag forwarding distinct from IP forwarding • May make non-shortest paths • Tag routing linked to IP routing IP Forwarding LER (Perform Tagging) LSR Cloud (Forward by tag) IP Forwarding LER (Remove Tag) LSR Cloud (Forward by tag)

10. 13 Payload MPLS Header • Lightweight • 8 bit TTL • 20 bit label tag • 3 bit QoS tag • 1 bit stack • Indicates last LSR tag • Allows heirarchial tagging 13 Payload 5 13 Payload 8 13 Payload

11. Provisioning vs. Signalling • Signalling • Seconds • Provisioning • Minutes to days • Separate control message protocol • Distribute labels and forwarding info • RSVP • Label Distribution Protocol

12. Comparing MPLS to IP • IP over MPLS vs IP only • Qos • Performance • Tunneling • VPN • Traffic Engineering

13. MPLS vs IP: QoS • MPLS • Per hop QoS • Using labels to prioritize • 20 bit identifier space • IP • Per hop QoS • Use IP&TCP header • 104 bit identifier space

14. MPLS vs IP: Performance • MPLS • Forward on short tags • Not prefix match on address • IP • Routers can forward at gigabit/s

15. MPLS vs IP: Tunneling • MPLS • Lightweight tunnels • 32 bit header • IP • Heavyweight tunnels • ~160 (?) bit header

16. MPLS vs IP: VPN • MPLS • Lightweight • 32 bit header • No security • IP • Heavyweight • ~160 (?) bit header • No security • (without IPSEC)

17. MPLS vs IP: Traffic Engin. • MPLS • Arbitrary (non-shortest) paths • Virtual circuits • MPLS routing linked to IP routing • Flexible aggregation • IP • Route announcement manipulation • Path cost manipulation

18. MPLS vs IP: Future QoS • MPLS • Propagate QoS between networks • RSVP • IP • Propagate QoS between networks • RSVP

19. Compelling Advantages • Traffic engineering • Management engine • Connectivity • Policy • Constraint based routing • Construct virtual topology • LSP’s • Labels