Subject: [Mpls-interop] Which type of signaling OAM or CP?

From: Lou Berger <[email-masked]>
Date: Thu, 20 Nov 2008 14:08:06 -0600

So you might have noticed that I raised this question in yesterdays meeting.

We have some related requirements that say:
(requirements draft)
    12  The MPLS-TP data plane MUST be capable of functioning
        independently of the control or management plane used to operate
        the MPLS-TP layer network.  That is the MPLS-TP data plane
        operation MUST continue to operate normally if the management
    ...
    39  The MPLS-TP control pane MUST support the configuration and
        modification of OAM maintenance points as well as the activation/
        deactivation of OAM when the transport path is established or
        modified.
    ...
    46  MPLS-TP MUST support inband OAM driven protection mechanisms
        (without any dependency on a control plane) to enable fast
        recovery from failure.
    ...
    47  G.  Operator requests for manual control of protection switching
            such as clear, lockout of protection, forced-switch and
            manual-switch commands MUST be supported.  Prioritized
            protection between Signal Fail (SF), Signal Degradation (SD)
            and operator switch requests MUST be supported.

(OAM req. draft)
    OAM functions MUST operate and be configurable even in the absence of
    a control plane. Conversely, OAM functions SHOULD be configurable as
    part of connectivity (LSP or PW) management. Note that means for
    configuring OAM functions and for connectivity management are outside
    the scope of this document.
    ...
    The MPLS-TP OAM tool-set MUST provide a function to enable service
    providers to verify bandwidth throughput (and other diagnostic tests)
    between a pair of MEPs.

So the question is which MPLS-TP related OAM/diagnostic functions 
need to be implemented in a management interface, which in control 
plane signaling and which in OAM signaling?

Clearly some functions will need to be supported via more than one 
mechanism (e.g., LSP setup via management and CP).  The list of 
functions I showed in WG is:
   +-----------------------------------------------------+---+-----+-----+
   |    Function                                         |MP | CP  | OAM |
   +-----------------------------------------------------+---+-----+-----+
   |1.  LSP setup / tear down                            | Y |  Y  |  N  |
   |2.  Signaling restoration (not pre-planned)          | N |  Y  |  N  |
   |3.  Enabling OAM                                     | Y |  Y  |  N  |
   |4.  Fault detection (data plane)                     | N |  N  |  Y  |
   |5.  FIS and Coordinated bidirectional switch         | N |  N* |  Y  |
   |6.  Reversion                                        | N |  N* |  Y  |
   |7.  Protection commands                              |   |     |     |
   |    (clear, lockout, forced-switch and manual-switch)| Y |  Y  | ??? |
   |8.  Loopback control                                 | Y | ??? | ??? |
   |9.  AIS                                              | N |  N* |  Y  |
   |10. Alarm free setup/teardown                        | Y |  Y  | ??? |
   +-----------------------------------------------------+---+-----+-----+

MP  = management plane interface
CP  = Control plane signaling
OAM = OAM signaling

Anything marked with a 'Y' is my interpretation of what we've agreed 
to as being supported by a particular mechanism in the TP context.

Anything marked with a 'N' is my interpretation of what we've agreed 
to as being not being supported by a particular mechanism in the TP 
context. An asterisk '*' is used to denote functions that are already 
or have been proposed to be supported by GMPLS signaling.

'???' identifies those mechanisms that I think are open.

Please feel free to add to this list if you think I've missed something.

So, to be clear the questions I'm asking are:

A) Should the standard protection commands (req. 47 G) signaling via OAM?

B.1) Is support for **signaling** loopback control desired/required?
B.2) Via which signaling mechanism GMPLS or OAM?
      (Note that an OAM mechanism has been proposed in
       draft-boutros-mpls-tp-loopback-01.txt.  Also loopback control has
       been discussed as a generally useful GMPLS function and is
       available in some implementations, but has not been standardized.)

C) Should alarm free setup/teardown be signaled by OAM?  (Note, this is
    already supported in rfc3473.)

comments?

My opinion is:

A) No - already available in GMPLS
B.1) no strong opinion
B.2) GMPLS - this is a generally useful function an applicable beyond TP,
      e.g., in OTN/WSON networks
C) No - already available in GMPLS

Lou

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