Protection in OBS

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Protection in OBS

• Zartash Afzal Uzmi

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First slide

• This is not a tutorial!
• This is a discussion

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Outline

• More MPLS
• Labels
• Stacking labels
• GMPLS
• Protection in Optical Burst Switching (OBS)
• Restoration and Protection
• Protection in OBS
• Protection in MPLSOBS (labeled OBS)
• Food for thought

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Outline

• More MPLS
• Labels
• Stacking labels
• GMPLS
• Protection in Optical Burst Switching (OBS)
• Restoration and Protection
• Protection in OBS
• Protection in MPLSOBS (labeled OBS)
• Food for thought

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IP versus MPLS

• In IP Routing, each router makes its own routing
  and forwarding decisions
• In MPLS
• source router makes the routing decision
• Routing finding shortest path to destination!
• Intermediate routers make forwarding decisions
• A path is computed and a virtual circuit is
  established from ingress router to egress router
• An MPLS path or virtual circuit from source to
  destination is called an LSP (label switched path)

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MPLS Forwarding

• In MPLS, a label is attached with IP datagrams at
  the ingress router
• Intermediate MPLS routers make forwarding
  decision based on the label
• You can even stack the labels!

IP Datagram
Label
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MPLS Label Stacking

• Label stacking is useful for aggregating traffic
• It is also useful in n1 protection routing
• Intermediate MPLS routers usually look at the
  topmost label

IP Datagram
Label
Label
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Generalized MPLS (GMPLS)

• In MPLS, label is a sequence of bits and is
  attached with the IP packet
• MPLS ?Forwarding is decided by the label
• Forwarding may be decided based on
• Time slot
• Wavelength
• Incoming port
• These all are examples of GMPLS
• Forwarding based on burst control packet?

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Outline

• More MPLS
• Labels
• Stacking labels
• GMPLS
• Protection in Optical Burst Switching (OBS)
• Restoration and Protection
• Protection in OBS
• Protection in MPLSOBS (labeled OBS)
• Food for thought

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Protection and Restoration

• Restoration
• On-demand recovery no preset backup paths
• Example existing recovery in IP networks
• Protection
• Pre-determined recovery backup paths in
  advance
• Primary and backup are provisioned at the same
  time
• IP supports restoration
• Because it is datagram service
• MPLS supports restoration as well as protection
• Because it is virtual-circuit service
• What should be used in OBS? Restoration?
• Burst is too fast to sustain restoration
  latencyNO!

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Protection in OBS

• 11 or n1 protection is useful for circuits
• Either optical circuits or virtual circuits or
  the LSPs
• In non-circuit architectures such as OBS
• Usually 11 protection is used
• Other schemes are also possible

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Outline

• More MPLS
• Labels
• Stacking labels
• GMPLS
• Protection in Optical Burst Switching (OBS)
• Restoration and Protection
• Protection in OBS
• Protection in MPLSOBS (labeled OBS)
• Food for thought

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MPLSOBS

• In MPLSOBS
• Two LSPs are created for each incoming LSP
  request
• One LSP for the BCP
• One LSP for the Burst itself
• In GMPLSOBS
• Switching can be on some basis
• Label associated with the IP packet (Labeled OBS)
• Anything else such as wavelength, timeslot, port,
  etc.
• Labeled-OBS is a special case of GMPLSOBS

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GMPLS out-of-band signaling

• GMPLS control channel
• Routing
• Signaling
• Link management
• These functions use IP based Routing/forwarding
• GMPLS data channel
• Typically label-swapped
• Can be wavelength-swapped, fiber-swapped, etc.
• Both BCP and Burst use the data channel

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GMPLSOBS and Faults

• Labeled OBS is a specific case of GMPLSOBS
• What happens in case of fault?
• Both BCP and Burst need re-routing
• May lead to longer paths
• Offset may not be enough
• If only BCP path fails
• Recovery time is extremely important
• Recovery time at a node is included in processing
  time
• Only local protection makes sense!
• What if only Burst path fails?
• If Burst path not recoverable, then BCP should be
  dropped!

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Last slide

• Discussion!