MPLS-TP Loopback
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MPLS-TP Loopback Draft draft-boutros-mpls-tp-loopback-01.txt Sami Boutros Siva Sivabalan George Swallow David Ward Rahul Aggarwal Nabil Bitar. Background. This draft specifies how to put an MPLS-TP LSP into and out-of loopback mode. This extension specifies two forms of the mode

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MPLS-TP Loopback Draftdraft-boutros-mpls-tp-loopback-01.txtSami Boutros Siva Sivabalan George SwallowDavid WardRahul AggarwalNabil Bitar


Background
Background

  • This draft specifies how to put an MPLS-TP LSP into and out-of loopback mode.

  • This extension specifies two forms of the mode

    • Intrusive: loop all traffic (including data)

      or

    • Non-instrusive only OAM messages, not data traffic


Problem Definition

MPLS Bidirectional LSP

LSR-1

LSR-3

LSR-2

Consider the above scenario:

We have a bidirectional MPLS LSP going from LSR-1 to LSR-2 to LSR-3.

LSR-1 and LSR-3 are acting as MEPs and terminating the Bidirectional MPLS-LSP and LSR-2 is acting as a MIP.

Traffic would flow on the LSP from LSR-1 to LSR-3


Problem Definition Continued…

MPLS Bidirectional LSP

LSR-1

LSR-3

LSR-2

Need to put MPLS bidirectional LSP in Loopback mode

Assume we need on LSR-2 to put the LSP in Full Loopback (FLB) or OAM Loopback mode (OLB).

In FLB mode, data traffic sent from LSR-1 will be looped back to LSR-1.

In OLB mode, data traffic will not be looped back.

In both modes, the MPLS OAM Loopback message will be received by LSR-2, and an Ack will be sent back to LSR-1.


Proposed Solution : LSP into Non-Intrusive Loopback Mode

MPLS Bidirectional LSP

LSR-1

LSR-3

LSR-2

LSR-1 sends an OAM Loopback Request

to LSR-2, the message contains the LSR-2 ID

MPLS-OAM Message TTL expired at LSR-2, LSR-2

matches the ID and sends an ack back to LSR-1

  • OAM intercepted at MIP obecause TTL expiry

  • target id used to match the MIP address

  • if no match, send NACK.


Proposed Solution: LSP into Intrusive Loopback Mode

MPLS Bidirectional LSP

LSR-1

LSR-3

LSR-2

LSR-1 sends a Lock Request to LSR-3

to take the MPLS LSP out of service

LSR-3 takes the MPLS-LSP out of service from

dataplane and sends an Ack back to LSR-1

LSR-1 sends a Loopback Request to LSR-2

To put the MPLS LSP in Full Loopback mode

LSR-2 setup dataplane to loopback traffic received

on this LSP from LSR-1 and sends an ack back to LSR-1


Proposed Solution: Intrusive Loopback Mode, flow of data packets

MPLS Bidirectional LSP

LSR-1

LSR-3

LSR-2

LSR-1 sends data packets on the MPLS

Bidirectional LSP to test connectivity up

to LSR2, Packets may contain a sequence #’s.

LSR-2 Loops back the packets sent to LSR-1

LSR-1 could check sequence #’s on packet received

to guarantee no losses


Proposed Solution: Out-of Intrusive Loopback Mode

MPLS Bidirectional LSP

LSR-1

LSR-3

LSR-2

LSR-1 sends a Loopback removal

Request to LSR-2

LSR-2 setup dataplane to remove the Loopback

On the MPLS LSP and sends an Ack back to LSR-1

LSR-1 sends an unLock Request to LSR-3

To put the MPLS LSP back in Service

LSR-3 puts the MPLS LSP back in service

and sends an ack back to LSR-1


Putting mpls tp in loopback using nms
Putting MPLS-TP in Loopback using NMS

An operator should be able to provision any given LSR to:

  • Lock/Unlock any MPLS-TP LSP.

  • Setup any MPLS-TP LSP in loopback mode (either FLB or OLB).

  • Send MPLS OAM packets from a MEP and notify NMS when MPLS OAM response arrives.

    When NMS is used to provision any of the above the

    functionality, the corresponding MPLS OAM message is

    not used.


Proposed solution mpls oam message extensions
Proposed Solution MPLS OAM Message extensions

The proposed mechanism is based on a set of new TLVs

which can be transported using one of the following

methods:

  • Using in-band MPLS OAM messages which are forwarded as MPLS packets (non-IP based).

  • Using LSP-Ping messages where IP/UDP packets are used (IP-based) in compliance with RFC 4379.


Proposed Solution new ACH codepoint for in-band option.

The ACH with "MPLS-TP Looback" code point (TBD) indicates the message type

A 32-bit field is added to carry the message ID

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

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

|0 0 0 1 |0 0 0 0 |0 0 0 0 0 0 0 0 | 0xHH (MPLS-TP Loopback) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Message ID | Message Length |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: MPLS-TP OAM Message Header


Proposed Solution new TLVs to be added..

  • Lock Request TLV

  • Unlock Request TLV

  • Loopback Request TLV (with a flag saying FLB or OLB)

  • Loopback Removal TLV

  • Authentication TLV

  • Source Identifier TLV (not need in IP MPLS-OAM message version).

  • In compliance with RFC 4379

  • Target Identifier TLV (needed to verify that the Loopback OAM message is meant for this node).

    • In compliance with RFC 4379

  • Response TLV


  • Lspv option control packet format
    LSPV option control packet format

    • 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

    • +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    • | MPLS Label Stack for the MPLS-LSP … |

    • +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    • | Label with EOS bit set |

    • +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    • | IP Hdr |

    • +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    • | UDP Hdr |

    • +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    • | TLV’s … |

    • +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    • Compliant with RFC 4379, 5085, draft-ietf-pwe3-ms-pw-requirements-07

    • cc_type used at MEP & MIP

    • CW, RA and TTL cc_type at MEP

    • Only TTL at MIP

    • Reply can come back as IP or MPLS.


    In band option control packet format
    In-band Option control packet format

    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

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    | MPLS Label Stack for the MPLS-LSP … |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    | Label with EOS bit set |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    |0 0 0 1 |0 0 0 0 |0 0 0 0 0 0 0 0 | 0xHH (MPLS-TP Loopback) |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    | Message ID | Message Length |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    | TLV’s … |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    The assumption is that LSP is bidirectional or moral equivalent


    Optional data packet extension in intrusive mode
    Optional data packet extension in Intrusive mode

    • In FLB mode, data packets looped back to TX MEP.

    • Packets may contain a sequence-id to insure order

      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

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      | MPLS Label stack |

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      | Label with EOS bit set |

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      | Optional Sequcence-ID |

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


    Future enhancements
    Future Enhancements

    • Clarify LSP-Ping usage as it MUST be supported

    • Add code point to loop OAM packets in OLB mode.

    • Make Lock a MUST in FLB mode.

    • GAL used to allow OAM control packets to pass through the LSR that loops back packets in FLB mode.

    • Optional (TBD): Set of functions for the data packets, to measure delay, packet loss, etc.


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