RFC 3429 (rfc3429) - Page 2 of 6

Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions

RFC 3429           OAM Alert Label for OAM Functions       November 2002


   -  Reporting the defect/failure information: Defect information is
      given to other management entities (e.g., Operation Support
      System) in order to provide the appropriate indications to the
      maintenance staff for maintaining the Quality of Service (QoS)
      level offered to customers.

   -  Defect/failure localization: Determination by internal or external
      test systems of a failed entity is performed if defect information
      is insufficient.

   -  Performance monitoring: Performance (packet losses, transfer
      delay, bit errors, etc.) of the user information transport is
      measured in order to estimate the transport integrity.

3. OAM Packet Identification

   The user-plane MPLS OAM mechanisms as described in the ITU-T
   Recommendation Y.1711 [1] uses a special label called 'OAM Alert
   Label' to differentiate OAM packets from the normal user packets.
   One of the reserved label values defined in RFC 3032 (MPLS label
   stack encoding [2]) is assigned to 'OAM Alert Label'.  A value of 14
   is used for this purpose.

4. MPLS OAM work in ITU-T SG13

   ITU-T Study Group 13, Question 3/13 is progressing work on user-plane
   MPLS OAM and has produced the following documents:

   (1) Recommendation Y.1710 (Requirements for OAM functionality for
       MPLS networks) [3]

   (2) Corrigendum 1 to Recommendation Y.1710 [4]

   (3) Recommendation Y.1711 (OAM mechanisms for MPLS networks) [1]

   (4) Draft Recommendation Y.1720 (Protection switching for MPLS
       networks) [6] relies on OAM mechanisms in Y.1711, under last call
       as of Nov. 2002.

5. Considerations on penultimate hop popping (PHP)

   In response to concerns raised during IETF meetings and in related
   discussions, this section provides an explanation on how MPLS OAM
   functions defined in ITU-T Recommendation Y.1711 [1] are applied to
   MPLS networks where PHP is in effect.






Ohta                         Informational