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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

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Mpls the magic behind the myths

MPLS: The Magic Behind the Myths

Grenville Armitage (author)

Scott Crosby (presenter)


Problems with ip
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 ip1
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 ip2
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


Problems with ip3
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
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 mpls1
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

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


Other features of mpls
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

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


Provisioning vs signalling
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
Comparing MPLS to IP

  • IP over MPLS vs IP only

    • Qos

    • Performance

    • Tunneling

    • VPN

    • Traffic Engineering


Mpls vs ip qos
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 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 vs IP: Tunneling

  • MPLS

    • Lightweight tunnels

      • 32 bit header

  • IP

    • Heavyweight tunnels

      • ~160 (?) bit header


Mpls vs ip vpn
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 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 vs IP: Future QoS

  • MPLS

    • Propagate QoS between networks

    • RSVP

  • IP

    • Propagate QoS between networks

    • RSVP


Compelling advantages
Compelling Advantages

  • Traffic engineering

    • Management engine

      • Connectivity

      • Policy

      • Constraint based routing

      • Construct virtual topology

        • LSP’s

        • Labels


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