Multiprotocol Lambda Switching

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Multi-protocol Lambda Switching

• Harini Krishnamurthy
• DAWN Lab
• School of EECS, WSU, Pullman

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Multi-protocol Label Switching (MPLS)

• is a connection-oriented switching service
• can be considered as a layer between the link
  layer
• and the network layer is NOT itself a
  routing
• protocol
• is independent of both routing protocols and
• link layer protocols
• uses existing routing protocols like OSPF, BGP,
  etc.

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MPLS some terms

• Label
• - fixed-length entity associated with a stream
• Forwarding Equivalence Class (FEC)
• - a group of layer 3 packets forwarded in the
  same
• manner
• Label Switching Router (LSR)
• - a router capable of switching based on
  labels
• Label Switched Path (LSP)
• - a path from source to destination formed
  based
• on label switching
• Label Distribution Protocol (LDP)
• - a protocol used by an LSR to perform
  neighbor
• discovery and distribute the labels

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MPLS Operation
LSR
MPLS domain
Non - LSR
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MPLS Operation contd.

• Carrying the label in the packet

Link Layer header
MPLS shim Label header
Network Layer header
Network Layer data

• Each LSR maintains a forwarding table
• A typical forwarding table entry

Outgoing label Outgoing interface Next hop address
Incoming label

• Label swapping
• Label format

TTL (8)
Label (20 bits)
Experimental (3)
Stack (1)
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Label Distribution

• used by LSRs to inform each other of the labels
• assigned to the packets
• The protocol used is LDP
• LDP has to do two things
• neighbor discovery
• label distribution
• LDP uses UDP for neighbor discovery and TCP
• for exchange of label information
• LSRs update their forwarding tables based on
  this
• information

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Benefits of using MPLS

• Forwarding packets between different types of
• networks is simplified to a great extent,
  because there
• is a single forwarding algorithm irrespective
  of the
• routing or link layer protocol used.
• Switching based on short labels is an advantage
  over
• long headers.

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Multi- protocol Lambda Switching (MPLambdaS)

• is an extension of MPLS to lend support to
• optical networks
• the LSR, in this case, is an optical
  crossconnect (OXC)
• the label used in MPLambdaS is the wavelength
  that
• the data is transmitted on
• just as an LSR maps an incoming label to an
  outgoing
• one, the OXC maps an incoming wavelength to an
• outgoing wavelength
• OXCs need routing protocols and label
  distribution
• protocols

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Benefits of MPLambdaS

• allows for data networks to communicate through
• an optical core
• exploits the existing MPLS framework, so that
• something entirely new is not needed

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Best Effort Switching

• a framework for routing using MPLambdaS for
  legacy
• networks that coexist with optical WDM
  networks
• uses wavelengths as labels
• Each router (OXC) has 2 components
• - Legacy Plane for packet switched protocols
• - Optical Plane for high speed optical switching

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BES Some terms

• OXC
• - performs the function of an LSR
• Control channel
• - a channel on a dedicated wavelength for
  transmitting
• control information
• Switching wavelengths
• - data on these wavelengths is switched in the
  optical
• domain
• Routing wavelengths
• - requires O/E conversion, a route lookup and
  E/O
• conversion at the end host

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BES operation in the Optical plane

• Nodes use the control channel to pass route
  updates
• The label forwarding table is generated using
  these
• routing updates
• The OXC obtains the switching matrix that it
  uses to
• switch, from the label forwarding table

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Routing using BES

• Statically switched paths
• Dynamically switched paths
• - Explicitly switched paths
• - ingress node specifies the entire path

2
3
6
1
A
B
4
5
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Routing using BES contd.

• Shared Switched Paths
• - 2 data streams meant for different
  destinations can
• use the same path for some part and then be
  routed
• separately to their respective destinations

2
3
6
1
A
B
4
5
1 to 2 - switched wavelength 2 to 5 routing
wavelength
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Summary

• MPLS
• MPLambdaS
• BES