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

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Bi-directional Symmetric LSP

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Bi directional symmetric lsp

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


Bi directional symmetric lsp

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


Benefits of bi directional symmetric lsp

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


Rsvp te extension

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


Cspf extension

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


Closing remarks

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.


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