The MPLS WG Archive

[Adrian Farrel <AF@dataconnection.com>]

Hi all,

After further discussion with John Drake, et al. and recent discussion on
the list of the subject, it seems appropriate to write down some thoughts on
controlling the target of the Notify so that (e.g.) the repair point in
protection switching does not need to be the initiator.  I'd like to suggest
the text below.

It is worth adding to this text that some consideration should be given to
flagging whether the initiator/responder support the use of Notify.  Whether
this should be achieved simply by the presence or absence of the new TLV
shown below (and suitable modification of the text) or by the inclusion of a
new flag in the SESSION_ATTRIBUTES is left as an exercise for the reader

=============

5.2. Notify Target

   A new object, the Notify Target object, MAY be added to the Path and
   Resv messages to specify the intended recipient of any Notify message
   that is generated to report an error on an LSP.

   If this object is not present, the node isolating the error condition
   must send the Notify to the initiator if it is upstream (on the
   initiator side) of the error, or to the terminator if it is
   downstream of the error.  In the case that a node is reporting an
   error that is local to itself, it must send a Notify in both
   directions.

   The Notify Target object provides better control of the recipients of
   Notify messages by allowing them to be specified when the LSP is set
   up.  The Path message may carry a Notify Target object to specify the
   IP address to which the Notify should be sent in lieu of the
   initiator when the error is isolated by a node upstream of the error.
   The Notify Target object on the Resv indicates the IP address to
   which the Notify should be sent when the error is isolated by a node
   downstream of the error.

   The target of the Notify may be changed at each hop as the Path and
   Resv are progressed through the LPS setup.  This includes adding such
   an object if it is not already present.  This facilitates many
   functions including restoration by intermediate nodes.

   A flag in the Notify Target object locks the target so that it may
   not be updated by subsequent nodes.


5.2.1. Required Information

   The Path message carries the Notify Target object as follows.

   <Path message> ::=  ..TBS based on GMPLS re-definition of Path

   ..Notify Target is added to <sender descriptor> in the following
     manner

      <sender descriptor> ::=  <SENDER_TEMPLATE> <SENDER_TSPEC>
                               [ <ADSPEC> ]
                               [ <RECORD_ROUTE> ]
                               [ <NOTIFY_TARGET> ]


   The Resv message carries the Notify Target object as follows.


   <Resv message> ::=  ..TBS based on GMPLS re-definition of Resv

   Notify Target is added to flow descriptor etc. as described above.

   The format of a Notify Target (in RSVP) is:

       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 (xx)| C_Type (xx)   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Reserved                             |L|D|E|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Notify Target                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Reserved

         This field is reserved.  It MUST be set to zero on transmis-
         sion and ignored on receipt.

      L - Lock

         Locks the Notify Target so that it may not be updated by
         subsequent nodes processing this message.

      D - Default

         Use the default target address (initiator or terminator) and
         disregard the value in the Notify Target field.

      E - Error Processing

         Send an error message (PathErr or ResvErr) as well as sending a
         Notify message.

      Notify Target

         Address to which a Notify should be sent if an error is
         isolated.


--
Adrian Farrel  mailto:af@datcon.co.uk
Network Convergence Group
Data Connection Ltd., Chester, UK
http://www.datcon.co.uk/
Tel: +44 (0) 1244 313440  Fax: +44 (0) 1244 312422