Bi-directional LSPs For Classical MPLS draft-dube-bidirectional-lsp-00/01.txt Rohit Dube, Michele Costa (Previously presented at MEF and MPLS WG)

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Bi-directional LSPs For Classical
MPLSdraft-dube-bidirectional-lsp-00/01.txtRohit
Dube, Michele Costa (Previously presented at MEF
and MPLS WG)
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Bi-directional Symmetric LSP

• Definition
• A symmetric bi-directional LSP has the same
  traffic engineering requirements for both
  directions including fate sharing, protection and
  restoration, LSRs, and resource requirements
  (e.g. latency and jitter). GMPLS-Architecture
• A symmetric bi-directional LSP also uses the
  same path through the network for both directions
• Current Status
• GMPLS supports Bi-directional LSP
• Classical MPLS does not
• Two unidirectional Classical LSPs required for
  bi-directional communication
• Proposal
• Extend RSVP-TE to enable Bi-directional LSPs for
  Classical MPLS

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Benefits of Bi-directional Symmetric LSP

• Best fit for applications that require
  connectivity in both directions
• Pseudo-wire emulation
• MEF EVPL
• Better Manageability
• Less configuration
• Simplify adding new sites to a VPN
• Easier fault isolation
• Better Scalability
• Less LSP state
• Less LSP setup and maintenance messages
• Lower LSP setup latency

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RSVP-TE extension

• Add Support of UPSTREAM_LABEL object in PATH
  message for the label to be used in the reverse
  direction
• 0 1
  2 3
• 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
  1 2 3 4 5 6 7 8 9 0 1
• -------------------------
  -------
• Length
  Class-Num (26) C-Type (1)
• -------------------------
  -------
• Label
  
  
• ...
  
  
• -------------------------
  -------
• Class-Num 26 UPSTREAM_LABEL
• C-Type 1 Regular Label

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CSPF Extension

• Constrained-based Shortest Path First (CSPF)
  usually calculates a path to meet the traffic
  engineering constraints in the forwarding
  direction.
• Adequate for IP traffic-engineering TE for
  uni-directional LSP, due to the asymmetrical
  nature of the underlying IP traffic.
• CSPF Implementation Extension
• Be able to calculate a strict explicit path which
  meets the traffic engineering constraints in both
  forwarding and reverse directions for
  bi-directional symmetric LSP.
• No extensions required to routing standards
• OSPF-TE already conveys the necessary information
  for a bi-directional CSPF calculation

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Closing Remarks

• Proposal extends LSP setup mechanism
• thus fits in MPLS WG
• presented to PWE3 for information
• Proposal being extended to support asymmetric
  bandwidth reservation
• 01 version will be submitted soon.
• An UPSTREAM_FLOWSPEC object is defined which
  carries the reverse path reservation information
  in the PATH message.