Multi Protocol Label Switching

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Multi Protocol Label Switching

• By Kiran Diwakar
• Guide Prof. Krishna Paul

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Agenda

• Motivation and Introduction.
• Some Basic Terminology
• Working
• Application to Traffic Engineering.

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Motivation

• IP forwarding is destination based.
• Longest Prefix Match of hierarchical addresses.
• Search Time becomes bottleneck.
• Different Forwarding techniques.

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So why MPLS ?

• Elegant.
• Faster. How ?
• - Flat labels,Indexed lookup exact match

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History

• Many approaches to label switching were
  proposed
• a.  Toshiba Cell Switching Router
  (1994)
• b.  Cisco Tag Switching (1996)
• c.   Ipsilon Tag Switching (1996)
• d.   IBM Aggregate Route-based IP
  Switching (ARIS) (1996)
• MPLS working group was established in
  96 and IETF charter was passed in 97.
• Finally the name MPLS was accepted
  because neutral name was required.

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Terminology

• Label Edge Router ( LER)
• Label Switch Router (LSR)

• Forward Equivalence Classes ( FEC ) Group of
  packets . - Different granularities.

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Terminology cont.

• Label 20 bit entity
• Label Switched Paths (LSP) Paths actually taken
  by the packets in MPLS domain.

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Setting Up an LSP

• Hop by Hop Normal LDP method.
• Explicit Routing Entire path is mentioned at
  the ingress.

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Label Distribution Protocol

• Label Request - Label for FEC .

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Label Binding Types

• What is binding ?
• Local Binding Label assigned and used by the
  router locally.
• Remote binding Router receives bindings from
  some other user.

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Application to Traffic Engineering

• Some links congested while some links under
  utilized.

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Constraint Based Routing

• Find a path that satisfies constraints.
• - Attributes / Properties
• - Example attributes bandwidth, delay.
• Traffic Trunks used instead of the individual
  flows.

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Working

• Finds Shortest path tree using algorithm

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Final Shortest Tree

• Either BC or CD can be removed.

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Modifications for CSPF

• Along with distance check for constraints.
• Issues with multiple attributes.
• Constraint f ( a1,a2,a3.)
• What soln we get after applying constraint on
  parameter a1,we apply the next constraint on a2
• Attributes are ordered as per priority policy
  decision

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Distribution of Attributes

• How to distribute the attributes?
• Can be piggybacked on routing updates.
• Can use flooding mechanism like link state.
• Issue of network clogging.
• Can have a threshold after which flood.

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CR-LDP

• It adds Explicit Routing Capability to LDP.
• Needs link state protocol.
• Creates ERO along with label request.
• ERO inserted into label request message.

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Rerouting

• Why rerouting necessary?
• Problems with plain IP rerouting.

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MPLS CR for Rerouting

• Label Stacking Capability is used.

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Benefits

• Separation of two planes.
• What is the benefit?
• Protocol Independence
• Flexibility
• Modularity and hence scalability
• Layer2 performance and Layer3 connectivity
• Improves the price / performance characteristics

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MPLS Products

• Cisco Both Edge and Core MPLS routers are
  available. Traffic Engineering support is
  provided.
• Nortel Networks preserves the utility of existing
  service provider infrastructure by linking
  traditional data networks to MPLS networks
• Data Connection Optical Networks

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Thank You !!!