Internet Engineering Task Force                             Luca Martini
Internet Draft                                               Monoski LLC
Intended status: Standards Track                          George Swallow
Expires: August 2017                                               Cisco
                                                        Elisa Bellagamba
                                                                Ericsson

                                                           February 2017


      MPLS LSP PW status refresh reduction for Static Pseudowires


                draft-ietf-pals-status-reduction-02.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on August 13, 2010

Abstract

   This document describes a method for generating an aggregated
   pseudowire status message transmitted on a Multi-Protocol Label
   Switching (MPLS) Label Switched Path (LSP) to indicate the status of
   one or more pseudowires carried on the LSP.

   The method for transmitting the pseudowire (PW) status information is
   not new, however this protocol extension allows a Service Provider
   (SP) to reliably monitor the individual PW status while not



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   overwhelming the network with multiple periodic status messages. This
   is achieved by sending a single cumulative summary status
   verification message for all the PWs grouped in the same LSP.



Table of Contents

    1        Introduction  .........................................   3
    1.1      Requirements Language  ................................   3
    1.2      Terminology  ..........................................   3
    1.3      Notational Conventions in Backus-Naur Form  ...........   4
    2        PW status refresh reduction protocol  .................   4
    2.1      Protocol states  ......................................   4
    2.1.1    INACTIVE  .............................................   5
    2.1.2    STARTUP  ..............................................   5
    2.1.3    ACTIVE  ...............................................   5
    2.2      Timer value change transition procedure  ..............   5
    3        PW status refresh reduction procedure  ................   6
    4        PW status refresh reduction Message Encoding  .........   6
    5        PW status refresh reduction Control Messages  .........   9
    5.1      Notification message  .................................  10
    5.2      PW Configuration Message  .............................  11
    5.2.1    MPLS-TP Tunnel ID  ....................................  12
    5.2.2    PW ID configured List  ................................  12
    5.2.3    PW ID unconfigured List  ..............................  13
    6        PW provisioning verification procedure  ...............  13
    6.0.4    PW ID List advertising and processing  ................  14
    7        Security Considerations  ..............................  14
    8        IANA Considerations  ..................................  15
    8.1      PW Status Refresh Reduction Message Types  ............  15
    8.2      PW Configuration Message Sub-TLVs  ....................  15
    8.3      PW Status Refresh Reduction Notification Codes  .......  16
    9        References  ...........................................  16
    9.1      Normative References  .................................  16
    9.2      Informative References  ...............................  17
   10        Authors' Addresses  ...................................  17














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1. Introduction

   When PWs use a Multi Protocol Label Switched (MPLS) network as the
   Packet Switched Network (PSN), they are setup according to [RFC8077]
   static configuration mode and the PW status information is propagated
   using the method described in [RFC6478]. There are 2 basic modes of
   operation described in [RFC6478] section 5.3: Periodic retransmission
   of non-zero status messages, and a simple acknowledge of PW status
   (sec 5.3.1 of [RFC6478]).  The LSP level protocol described below
   applies to the case when PW status is acknowledged immediately with a
   requested refresh value of zero (no refresh).  In this case the PW
   status refresh reduction protocol is necessary for several reasons,
   such as:

        -i. Greatly increase the scalability of the PW status protocol
            by reducing the amount of messages that a PE needs to
            periodically send to it's neighbors.
       -ii. Detect a remote PE restart.
      -iii. If the local state is lost for some reason, the PE needs to
            be able to request a status refresh reduction from the
            remote PE
       -iv. Optionally detect a remote PE provisioning change.


1.1. Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


1.2. Terminology

   FEC: Forwarding Equivalence Class

   LDP: Label Distribution Protocol

   LSP: Label Switching Path

   MS-PW: Multi-Segment Pseudowire

   PE: Provider Edge

   PW: Pseudowire

   SS-PW: Single-Segment Pseudowire

   S-PE: Switching Provider Edge Node of MS-PW



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   T-PE: Terminating Provider Edge Node of MS-PW


1.3. Notational Conventions in Backus-Naur Form

   All multiple-word atomic identifiers use underscores (_) between the
   words to join the words.  Many of the identifiers are composed of a
   concatenation of other identifiers.  These are expressed using
   Backus-Naur Form (using double-colon - "::" - notation).

   Where the same identifier type is used multiple times in a
   concatenation, they are qualified by a prefix joined to the
   identifier by a dash (-).  For example Src-Node_ID is the Node_ID of
   a node referred to as Src (where "Src" is short for "source" in this
   example).

   The notation does not define an implicit ordering of the information
   elements involved in a concatenated identifier.


2. PW status refresh reduction protocol

   PW status refresh reduction protocol consists of a simple message
   that is sent at the LSP level using the MPLS Generic Associated
   Channel.[RFC5586]

   A PE using the PW status refresh reduction protocol MUST send the PW
   status refresh reduction Message as soon as a PW is configured on a
   particular LSP.  The message is then re-transmitted at a locally
   configured interval indicated in the refresh timer field. If no
   acknowledgment is received, the protocol does not reach active state,
   and the PE SHOULD NOT send any PW status messages with a refresh
   timer of zero as described in [RFC6478] section 5.3.1.

   It is worth noting that no relationship is existing between the
   locally configured timer for the refresh reduction protocol and the
   PW individual status refresh timers.


2.1. Protocol states

   The protocol can be in 3 possible states: INACTIVE, STARTUP, and
   ACTIVE.








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2.1.1. INACTIVE

   This state is entered when the protocol is turned off. This state is
   also entered if all PW on a specific LSP are unprovisioned, or the
   feature is unprovisioned.


2.1.2. STARTUP

   In this state the PE transmits periodic PW status refresh reduction
   messages, with the Ack Session ID set to 0. The PE remains in this
   state until a PW status refresh message is received with the correct
   local session ID in the Ack Session ID Field. This state can be
   exited to the ACTIVE or INACTIVE state.


2.1.3. ACTIVE

   This state is entered once the PE receives a PW status refresh
   reduction message with the correct local session ID in the Ack
   Session ID Field within 3.5 times the refresh timer field value of
   the last PW status refresh reduction message transmitted. This state
   is immediately exited as follows:

        -i. A valid PW status refresh reduction message is not received
            within 3.5 times the current refresh timer field value.
            (assuming a timer transition procedure is not in progress)
            New state: STARTUP
       -ii. A PW status refresh reduction message is received with the
            wrong, or a zero, Ack Session ID field value. New state:
            STARTUP
      -iii. All PWs using the particular LSP are unprovisioned, or the
            protocol is disabled. New state: INACTIVE


2.2. Timer value change transition procedure

   If a PE needs to change the refresh timer value field while the PW
   refresh reduction protocol is in the ACTIVE state, the following
   procedure must be followed:
        -i. A PW status refresh reduction message is transmitted with
            the new timer value.
       -ii. If the new value is greater then the original one the PE
            will operate on the new timer value immediately.
      -iii. If the new value is smaller then the original one, the PE
            will operate according to the original timer value for a
            period 3.5 times the original timer value, or until the
            first valid PW status refresh reduction message is received.



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            A PE receiving a PW status refresh reduction message with a
            new timer value, will immediately transmit an acknowledge PW
            status refresh reduction message, and start operating
            according to the new timer value.


3. PW status refresh reduction procedure

   When the refresh reduction protocol, on a particular LSP, is in the
   ACTIVE state, the PE can send all PW status messages, for PWs on that
   LSP, with a refresh timer value of zero. This greatly decreases the
   amount of messages that the PE needs to transmit to the remote PE
   because once the PW status message for a particular PW is
   acknowledged, further repetitions of that message are no longer
   necessary.

   To further mitigate the amount of possible messages when an LSP
   starts forwarding traffic, care should be taken to permit the PW
   refresh reduction protocol to reach the ACTIVE state quickly, and
   before the the first PW status refresh timer expires. This can be
   achieved by using a PW status refresh reduction Message refresh timer
   value that is much smaller then the PW status message refresh timer
   value in use. (sec 5.3.1 of [RFC6478])

   If the refresh reduction protocol session is terminated by entering
   the INACTIVE or STARTUP states, the PE MUST immediately re-send all
   the previously sent PW status messages for that particular LSP for
   which the session terminated. In this case the refresh timer value
   MUST NOT be set to zero, and MUST be set according to the local
   policy of the PE router.


4. PW status refresh reduction Message Encoding

   The packet containing the refresh reduction message is encoded as
   follows: (omitting link layer information)















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    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 LSP (tunnel) Label Stack Entry             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              GAL                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 1|Version|   Reserved    | 0xZZ PW OAM Message           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Session ID           |         Ack Session ID        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Refresh Timer         |     Total Message Length      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Checksum              |    Message Sequence Number    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Last Received Seq Number     | Message Type  |U C Flags      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                     Control Message Body                      ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   This message contains the following fields:

     * PW OAM Message.

       This field indicates the Generic Associated Channel type in the
       GACH header as defined in [RFC5586].

       Note: Channel type 0xZZ pending IANA allocation.

     * Session ID

       A non-zero, locally selected session number that is not preserved
       if the local PE restarts.

       In order to get a locally unique session ID, the recommended
       choice is to perform a CRC-16 giving as input the following data

       |Y|Y|M|M|D|D|H|H|M|M|S|S|L|L|L|

       Where:  YY: are the decimal two last digit of the current year
       MM: are the decimal two digit of the current month DD: are the
       decimal two digit of the current day HHMMSSLLL: are the decimal
       digits of the current time expressed in (hour, minutes, seconds,
       milliseconds) If the calculation results in an already existing
       Session ID, a unique Session ID can be generated by adding 1 to



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       the result until the Session ID is unique.  Any other method to
       generate a locally unique session ID is also acceptable.

     * Ack Session ID

       The Acknowledgment Session ID received from the remote PE.

     * Refresh Timer.

       A non zero unsigned 16 bit integer value greater or equal to 10,
       in milliseconds, that indicates the desired refresh interval. The
       default value of 30000 is RECOMENDED.

     * Total Message Length

       Total length in octets of the Checksum, Message Type, Flags,
       Message Sequence Number, and control message body. A value of
       zero means that no control message is present, and therefore that
       no Checksum, and following fields are present either.

     * Checksum

       A 16 bit field containing the one's complement of the one's
       complement sum of the entire message (including the GACH header),
       with the checksum field replaced by zero for the purpose of
       computing the checksum. An all-zero value means that no checksum
       was transmitted. Note that when the checksum is not computed, the
       header of the bundle message will not be covered by any checksum.

     * Message Sequence Number

       An unsigned 16 bit integer number that is started from 1 when the
       protocol enters ACTIVE state. The sequence numbers wraps back to
       1 when the maximum value is reached. The value of zero is
       reserved and MUST NOT be used.

     * Last Received Message Sequence Number

       The sequence number of the last message received. In no message
       has yet been received during this session, this field is set to
       zero.

     * Message Type

       The Type of the control message that follows. Control message
       types are allocated in this document, and by IANA.





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     * (U) Unknown flag bit.

       Upon receipt of an unknown messageor TLV, if U is clear (=0), the
       keepalive session MUST be terminated by entering STARTUP state;
       if U is set (=1), the unknown message, or message contining a
       unknown TLV, MUST be acknowledged and silently ignored and the
       following messages, or TLVs, if any, processed as if the unknown
       message, or TLV did not exist.

     * (C) Configuration flag bit.  The C Bit is used to signal the end
       of PW configuration transmission. If it is set, the sending PE
       has finished sending all it's current configuration information.

     * Flags (Reserved)

       6 bits of flags reserved for future use, they MUST be set to 0 on
       transmission, and ignored on reception.

     * Control Message Body

       The Control Message body is defined in a section below, and is
       specific to the type of message.

   It should be noted that the Checksum, Message Sequence Number, Last
   Received Message Sequence Number, Message Type, Flags, and control
   message body are OPTIONAL. The length field is used to parse how many
   optional fields are included. Hence all optional fields that precede
   a specific field that needs to be included in a specific
   implementation MUST be included if that optional field is also
   included.

   If any of the above vaules are outside the specified range, a
   notification message is returned with a code "PW configuration not
   supported.", and the message is ignored.


5. PW status refresh reduction Control Messages

   PW status refresh reduction Control messages consist of the Checksum,
   Message Sequence Number, Last Received Message Sequence Number,
   Message Type, Flags, and control message body.

   When there is the need to send a PW status refresh reduction Control
   Messages, the system can attach it to a scheduled PW status refresh
   reduction or send one ahead of time. In any case PW status refresh
   reduction Control Messages always piggy back on normal messages.

   A PW refresh reduction message is also called a PW status refresh



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   reduction Control Message if it contains a  control message
   construct.

   There can only be one control message construct per PW status refresh
   reduction Message. If the U bit is set, and a PE receiving the PW
   status refresh reduction Message does not understand the control
   message, the control message MUST be silently ignored. However the
   message sequence number MUST still be acknowledged by sending a null
   message back with the appropriate value in the Last Message Received
   Field. If a control message is not acknowledged, after 3.5 times the
   value of the Refresh Timer, a fatal notification "unacknowledged
   control message" MUST be sent, and the PW refresh reduction session
   MUST be terminated.

   If a PE does not want or need to send a control message, the
   Checksum, and all following fields MUST NOT be sent, and the Total
   Message Length field is then set to zero.


5.1. Notification message

   The most common use of the Notification Message is to acknowledge the
   reception of a message by indicating the received message sequence
   number in the "Last Received Sequence Number" field. The notification
   message is encoded as follows:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Checksum              |    Message Sequence Number    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Last Received Seq Number     |  Type=0x01    |U   Flags      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Notification Code                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The message type is set to 0x01, and the U bit is treated as
   described in the above section. The Notification Codes are a 32 bit
   quantity assigned by IANA. (see IANA consideration section)
   Notification codes are either considered "Error codes" or simple
   notifications. If the Notification code is an Error code as indicated
   in the IANA allocation registry, the keepalive session MUST be
   terminated by entering STARTUP state. The 7 bits of flags are
   reserved for future use, they MUST be set to 0 on transmission, and
   ignored on reception.





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5.2. PW Configuration Message

   The PW status refresh reduction TLVs are informational TLVs, that
   allow the remote PE to verify certain provisioning information. This
   message contain a series of sub-TLVs in no particular order, that
   contain PW and LSP configuration information. The message has no
   preset length limit, however its total length will be limited by the
   transport network Maximum Transmit Unit (MTU). PW refresh reduction
   messages MUST NOT be fragmented. If a sender has more configuration
   information to send than will fit into one PW Configuration Message
   it may send further messages carrying further TLVs.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Checksum              |    Message Sequence Number    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Last Received Seq Number     |  Type=0x02    |U C (Flags)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   |                  PW Configuration Message Sub-TLVs            |
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The PW Configuration Message type is set to 0x02. For this message
   the U-bit is set to 1 as processing of these messages is OPTIONAL.

   The C Bit is used to signal the end of PW configuration transmission.
   If it is set, the sending PE has finished sending all its current
   configuration information. The PE transmitting the configuration MUST
   set the C bit on the last PW configuration message when all current
   PW configuration has been sent.

   PW Configuration Message Sub-TLVs have the following generic 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type        |  Length       |        Value                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   |                  Value Continued                              |
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+






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5.2.1. MPLS-TP Tunnel ID

   This TLV contains the address of the MPLS-TP tunnel ID. When the
   configuration message is used for a particular keepalive session the
   MPLS-TP Tunnel ID sub-TLV MUST be sent at least once.

   The MPLS Tunnel ID address is encoded as follows:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type=0x01   |  Length=20    |   MPLS-TP Tunnel ID address   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   |                  MPLS-TP Tunnel ID address  (20 Octets)       |
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The MPLS point to point tunnel ID is defined in [RFC6370] as follows:

   Src-Global_Node_ID::Src-Tunnel_Num::Dst-Global_Node_ID::Dst-
   Tunnel_Num

   Note that a single address is enough to identify the tunnel, and the
   source end of the message.


5.2.2. PW ID configured List

   This OPTIONAL TLV contains a list of the provisioned PWs on the LSP.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type=0x02   |    Length     |         PW Path ID            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         PW Path ID                            |
   ~                                                               ~
   |                         Continued                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The PW Path ID is a 32 octet pseudowire path identifier specified in
   [RFC6370] as follows: AGI::Src-Global_ID::Src-Node_ID::Src-AC_ID::
   Dst-Global_ID::Dst-Node_ID::Dst-AC_ID




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   The number of PW Path IDs in the TLV will be inferred by the length
   of the TLV up to a maximum of 8.  The procedure for processing this
   TLV will be described in a section below.


5.2.3. PW ID unconfigured List

   This OPTIONAL TLV contains a list of the PWs that have been
   unprovisioned on the LSP. Note that it is a fatal session error to
   send the same PW address in both the configured list TLV , and the
   unconfigured list TLV in the same configuration message. If the this
   error occurs, an error notification message is returned with the
   error code of "PW Configuration TLV conflict" and the session is
   terminated by entering STARTUP state.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type=0x03   |    Length     |         PW Path ID            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                        PW Path ID                             |
   ~                                                               ~
   |                         Continued                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The PW Path ID is a 32 octet pseudowire path identifier specified in
   [RFC6370] as follows: AGI::Src-Global_ID::Src-Node_ID::Src-AC_ID::
   Dst-Global_ID::Dst-Node_ID::Dst-AC_ID

   The number of PW Path IDs in the TLV will be inferred by the length
   of the TLV up to a maximum of 8.


6. PW provisioning verification procedure

   The advertisement of the PW configuration message is OPTIONAL.

   A PE that desires to use the PW configuration message to verify the
   configuration of PWs on a particular LSP, should advertise its PW
   configuration to the remote PE on LSPs that have active keepalive
   sessions.  When a PE receives PW configuration information using this
   protocol and it is not supporting or is not willing to use the
   information, it MUST acknowledge all the PW configuration messages
   with a notification of "PW configuration not supported". In this
   case, the information in the control messages is silently ignored. If
   a PE receives such a notification it SHOULD stop sending PW



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   configuration control messages for the duration of the PW refresh
   reduction keepalive session.

   If PW configuration information is received, it is used to verify the
   accuracy of the local configuration information against the remote
   PE's configuration information. If a configuration mismatch is
   detected, where a particular PW is configured locally but not on the
   remote PE, the following action SHOULD be taken:

        -i. The local PW MUST be considered in "Not Forwarding" State.

       -ii. The PW Attachment Circuit status is set to reflect the PW
            fault.

      -iii. An Alarm SHOULD be raised to a network management system.


6.0.4. PW ID List advertising and processing

   When configuration messages are advertised along a particular LSP,
   the PE sending the messages needs to check point the configuration
   information sent by setting the C bit when all currently known
   configuration information has been sent. This process allows the
   receiving PE to immediately proceed to verify all the currently
   configured PWs on that LSP, eliminating the need for a long waiting
   period.

   If a new PW is added to a particular LSP, the PE MUST place the
   configuration verification of this PW on hold for a period of at
   least 30 seconds. This is necessary to minimize false positive events
   of mis-configuration due to the ends of the PW being slightly out of
   sync.


7. Security Considerations

   The security considerations of [RFC6478] are adequate for the
   proposed mechanism since the operating environment is almost
   identical to the one where this protocol would be deployed. It should
   also be noted that since this protocol is designed to be deployed
   between two adjacent PEs connected by a physical link, it is not
   possible to misdirect or inject traffic without compromising the PW
   transport link itself. All these situations are covered in the
   security considerations of [RFC6478].







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8. IANA Considerations

   All the registries in this section are to be created or updated as
   appropriate in the Pseudowire Name Spaces (PWE3).


8.1. PW Status Refresh Reduction Message Types

   IANA needs to set up a registry of "PW status refresh reduction
   Control Messages". These are 8-bit values. Type value 1 through 2 are
   defined in this document. Type values 3 through 64 are to be assigned
   by IANA using the "Expert Review" policy defined in RFC5226. Type
   values 65 through 127, 0 and 255 are to be allocated using the IETF
   review policy defined in [RFC5226]. Type values 128 through 254 are
   reserved for vendor proprietary extensions and are to be assigned by
   IANA, using the "First Come First Served" policy defined in RFC5226.

   The Type Values are assigned as follows:
   Type   Message Description
   ----   -------------------
   0x01   Notification message
   0x02   PW Configuration Message


8.2. PW Configuration Message Sub-TLVs

   IANA needs to set up a registry of "PW status refresh reduction
   Configuration Message Sub-TLVs". These are 8-bit values. Type value 1
   through 2 are defined in this document. Type values 3 through 64 are
   to be assigned by IANA using the "Expert Review" policy defined in
   RFC5226. Type values 65 through 127, 0 and 255 are to be allocated
   using the IETF review policy defined in [RFC5226]. Type values 128
   through 254 are reserved for vendor proprietary extensions and are to
   be assigned by IANA, using the "First Come First Served" policy
   defined in RFC5226.

   The Type Values are assigned as follows:
   sub-TLV type    Description
   ------------    -----------
   0x01            MPLS-TP Tunnel ID address.
   0x02            PW ID configured List.
   0x03            PW ID unconfigured List.









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8.3. PW Status Refresh Reduction Notification Codes

   IANA needs to set up a registry of "PW status refresh reduction
   Notification Codes". These are 32-bit values. Type value 0 through 7
   are defined in this document. Type values 8 through 65536 are to be
   assigned by IANA using the "Expert Review" policy defined in RFC5226.
   Type values 65536 through 134,217,728, 0 and 4,294,967,295 are to be
   allocated using the IETF review policy defined in [RFC5226]. Type
   values 134,217,729 through 4,294,967,294 are reserved for vendor
   proprietary extensions and are to be assigned by IANA, using the
   "First Come First Served" policy defined in RFC5226.

   For each value assigned IANA should also track whether the value
   constitutes an error as described in Section 5.1. When values are
   assigned by IETF Review, the setting of this column must be
   documented in the RFC that requests the allocation. For Expert Review
   and FCFS assignments, the setting of this column must be made clear
   by the requester at the time of assignment.

   The Type Values are assigned as follows:
   Code        Error?  Description
   ----      ------  -----------
   0x00000000    No    Null Notification.
   0x00000001    No    PW configuration rejected.
   0x00000002    Yes   PW Configuration TLV conflict.
   0x00000003    No    Unknown TLV (U-bit=1)
   0x00000004    Yes   Unknown TLV (U-bit=0)
   0x00000005    No    Unknown Message Type
   0x00000006    No    PW configuration not supported.
   0x00000007    Yes   Unacknowledged control message.



9. References

9.1. Normative References

   [RFC2119] Bradner. S, "Key words for use in RFCs to
        Indicate Requirement Levels", RFC 2119, March, 1997.

   [RFC8077] "Pseudowire Setup and Maintenance Using the Label
        Distribution Protocol (LDP)", L. Martini, G. Heron, RFC8077,
        february 2017.

   [RFC6478] L. Martini, G. Swallow, G. Heron, M. Bocci "Pseudowire
        Status for Static Pseudowires", RFC6478, May 2012





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   [RFC6370] M. Bocci, G. Swallow, E. Gray "MPLS-TP Identifiers",
        RFC6370, September 2011

   [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
        IANA Considerations section in RFCs", BCP 26, RFC 5226, May 2008


9.2. Informative References

   [RFC5586] M. Bocci, Ed., M. Vigoureux, Ed., S. Bryant, Ed.,
        "MPLS Generic Associated Channel", rfc5586,  June 2009


10. Authors' Addresses


   Luca Martini
   Monoski LLC.
   e-mail: lmartini@monoski.com


   George Swallow
   Cisco Systems, Inc.
   300 Beaver Brook Road
   Boxborough, Massachusetts  01719
   United States
   e-mail: swallow@cisco.com


   Elisa Bellagamba
   Ericsson EAB
   Torshamnsgatan 48
   16480, Stockholm
   Sweden
   e-mail: elisa.bellagamba@gmail.com


Copyright Notice

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   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must



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Internet Draft  draft-ietf-pals-status-reduction-02.txt    February 2017


   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   Expiration Date: August 2017














































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