MPLS: The Magic Behind the Myths - Rice University

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

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

Tunnel IP over non-IP intermediate Virtual Private Network Abercr. CS IP Network Abercr. EE IP Network Duncan EE IP Network Duncan CS IP Network

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

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) 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 How Does MPLS Work? Packets are tagged and routed based on tags. All traffic with the same label treated the same

13 5 IP Routing Layer Payload Payload IP Routing Layer LSR LSR Payload

Payload 13 Payload 5 Payload LER LER LER LER 13 Payload

Payload 5 Payload Payload 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) 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 13 5 13

Payload 8 13 Payload Payload Provisioning vs. Signalling Signalling Seconds Provisioning Minutes to days

Separate control message protocol Distribute labels and forwarding info RSVP Label Distribution Protocol Comparing MPLS to IP IP over MPLS vs IP only Qos Performance

Tunneling VPN Traffic Engineering 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 MPLS vs IP: Performance MPLS Forward on short tags Not prefix match on address IP Routers can forward at gigabit/s MPLS vs IP: Tunneling MPLS Lightweight tunnels

32 bit header IP Heavyweight tunnels ~160 (?) bit header MPLS vs IP: VPN MPLS Lightweight 32 bit header No security IP Heavyweight ~160 (?) bit header

No security (without IPSEC) 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 MPLS vs IP: Future QoS MPLS Propagate QoS between networks RSVP IP Propagate QoS between networks RSVP

Compelling Advantages Traffic engineering Management engine Connectivity Policy Constraint based routing Construct virtual topology LSPs Labels