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Versions: (draft-xie-rserpool-enrp) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 RFC 5353

Network Working Group                                              Q. Xie
INTERNET-DRAFT                                                   Motorola
                                                            R. R. Stewart
                                                            Cisco Systems


Expires in six months                                        June 1, 2001


                 Enpoint Name Resolution Protocol (ENRP)
                  <draft-ietf-rserpool-enrp-00.txt>

Status of This Memo

    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC 2026. Internet-Drafts are
    working documents of the Internet Engineering Task Force (IETF), its
    areas, and its working groups. Note that other groups may also
    distribute working documents as Internet-Drafts.

    The list of current Internet-Drafts can be accessed at
    http://www.ietf.org/ietf/1id-abstracts.txt

    The list of Internet-Draft Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html.



Abstract

    Endpoint Name Resolution Protocol (ENRP) is designed to work in
    conjunction with the Aggregate Server Access Protocol (ASAP) [ASAP]
    to accomplish the functionality of the Reliable Server Pooling
    (Rserpool) requirements and architecture as defined in [RSERPOOL1]
    and [RSERPOOL2].

    Within the operational scope of Rserpool, ENRP defines the
    procedures and message formats of a distributed fault-tolerant
    registry service for storing, bookkeeping, retrieving, and
    distributing pool operation and membership information.


Table Of Contents

1. Introduction.................................................. 2
  1.2 Definitions................................................ 3
2. Conventions................................................... 4
3. ENRP Message Definitions...................................... 4
  3.1 PE Parameter Definition.................................... 4
  3.2 PEER_PRESENCE message...................................... 5
  3.3 PEER_NAME_TABLE_REQUEST message............................ 5
  3.4 PEER_NAME_TABLE_RESPONSE message........................... 6
  3.5 PEER_NAME_UPDATE message................................... 7
  3.6 PEER_LIST_REQUEST message.................................. 8
  3.7 PEER_LIST_RESPONSE message................................. 9

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  3.8 TAKEOVER_INITIATE message..................................10
  3.9 TAKEOVER_INITIATE_RESPONSE message.........................11
  3.10 TAKEOVER_PEER_SERVER message..............................11
  3.11 SERVER_DUMP message.......................................12
  3.12 SERVER_DUMP_RESPONSE message..............................12
4. ENRP Operation Procedures.....................................14
  4.1 Basic ENRP Operations......................................14
    4.1.1 PE Registration........................................14
    4.1.2 PE De-registration.....................................15
    4.1.3 Name Translation.......................................16
    4.1.4 Server Namespace Update................................16
      4.1.4.1 Add a New PE.......................................16
      4.1.4.2 Forceful Removal of a PE...........................17
      4.1.4.3 Advisory Removal of a PE...........................17
      4.1.4.4 Update PE Attributes...............................18
      4.1.4.5 Claim Ownership over a PE..........................18
      4.1.4.6 Report PE Communication Failure....................18
    4.1.5 PE Change Policy Value.................................19
    4.1.6 Server Download Namespace from a Peer Server...........19
    4.1.7 Server Monitor Peer Status.............................20
    4.1.8 Server Download Peer List from a Peer Server...........20
    4.1.9 ENRP Server Initialization.............................21
  4.2 Fault Management Operations................................21
    4.2.1 Detect and Report Unreachable PE.......................21
    4.2.2 ENRP Server Failure Detection by Heartbeat.............22
    4.2.3 PE Home ENRP Server Hunt...............................23
    4.2.4 ENRP Server Detecting and Taking-over Inactive Peer ...23
    4.2.5 Registration of Remote PEs.............................25
  4.3 Maintenance Operations.....................................25
    4.3.1 Forceful Removal of a PE...............................25
    4.3.2 Dump Home PE List......................................25
    4.3.3 Dump Remote PE List....................................26
    4.3.4 Dump Peer Server List..................................26
5.  Variables, Time Constants, and Thresholds....................26
  5.1 Variables..................................................26
  5.2 Timer Constants............................................26
  5.3 Thresholds.................................................27
6. References....................................................27
7. Acknowledgements..............................................27
8.  Authors' Addresses...........................................27


1. Introduction

    Endpoint Name Resolution Protocol (ENRP) is designed to work in
    conjunction with the Aggregate Server Access Protocol (ASAP) [ASAP]
    to accomplish the functionality of the Reliable Server Pooling
    (Rserpool) requirements and architecture as defined in [RSERPOOL1]
    and [RSERPOOL2].

    Within the operation scope of Rserpool, ENRP defines the procedures
    and message formats of a distributed fault-tolerant registry service
    for storing, bookkeeping, retrieving, and distributing pool
    operation and membership information.

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    Whenever appropriate, in the rest of this document we will refer to
    this Rserpool registry service as ENRP namespace, or simply
    namespace.


1.2 Definitions

    This document uses the following terms:

     Operation scope:
          The part of the network visible to pool users by a specific
          instance of the reliable server pooling protocols.

     Pool (or server pool):
          A collection of servers providing the same application
          functionality.

     Pool handle (or pool name):
          A logical pointer to a pool. Each server pool will be
          identifiable in the operation scope of the system by a unique
          pool handle or "name".

     ENRP namespace (or namespace):
          A cohesive structure of pool names and relations that may be
          queried by an internal or external agent.

     Pool element (PE):
          A server entity that runs ASAP and has registered to a pool.

     Pool user (PU):
          A server pool user that runs ASAP. Note, a PU can also be a
          PE if it has registered itself to a pool.

     ENRP namespace server (or ENRP server):
          Entity which runs ENRP and is responsible for managing and
          maintaining the namespace within the operation scope.

     ENRP maintenance client (or maintanance client):
          A special program that runs ASAP and has the additional
          capability of exchanging ENRP maintenance messages with an
          ENRP server in order to perform certain maintenance
          functions.

     Home ENRP server:
          The ENRP server to which a PE currently belongs. PEs
          normally choose the ENRP server on their local host as the
          home ENRP server, if one exists. A PU shall only have one
          home ENRP server at any given time, and both the PU and the
          home ENRP server shall keep track of this master/slave
          relationship between them.

     ENRP server takeover:
          The event that a remote ENRP server takes the ownership of

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          all the PEs on a node and becomes their new home ENRP
          server.

     Caretaker ENRP server:
          The ENRP server on a remote node which takes ownership of
          all PEs on the local node because of the absence of an
          active local ENRP server.

     ENRP client channel:
          The communication channel through which a PE requests for
          ENRP namespace service. The ENRP client channel is usually
          defined by the transport address of the home ENRP server and
          a well known port number.

     ENRP server channel:
          Defined by a well known multicast IP address and a well
          known port number. All ENRP servers in an operation scope
          can send multicast messages to other servers through this
          channel. PEs are also allowed to multicast on this channel
          occasionally.

     Network Byte Order:
          Most significant byte first, a.k.a Big Endian.


2. Conventions

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
   they appear in this document, are to be interpreted as described in
   [RFC2119].


3. Message Message Definitions

    All messages as well as their fields described below shall be in
    Network Byte Order during transmission. For fields with a length
    bigger than 4 octets, a number in a pair of parentheses may follow
    the filed name to indicate the length of the field in number of
    octets.


3.1 PE Parameter Definition

    This parameter is used in multiple ENRP message to represent an ASAP
    endpoint (i.e., a PE in a pool) and the associated information, such
    as its transport address(es), load control, and other operational
    status information of the PE.

    The parameter is defined to support PEs with up to 8 different IPv4
    transport addresses.

    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

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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        IP address #0                          |
    +-------------------------------+-------------------------------+
    |                        IP address #1                          |
    +-------------------------------+-------------------------------+
    \                     \                      \                  \
    /                     /                      /                  /
    \                     \                      \                  \
    +-------------------------------+-------------------------------+
    |                        IP address #7                          |
    +-------------------------------+-------------------------------+
    |          SCTP Port            |         Padding               |
    +-------------------------------+-------------------------------+
    |  Load sharing policy type     |       Policy Value            |
    +---------------+---------------+---------------+---------------+

    The total size of a PE parameter is 40 octets.


3.2 PEER_PRESENCE message

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |
    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+
    |                       Type = 0x100                            |
    +-------------------------------+-------------------------------+
    |                      sender's IP address                      |
    +-------------------------------+-------------------------------+
    |      sender's SCTP port       |         padding               |
    +-------------------------------+-------------------------------+
    |                    receiver's IP address                      |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+
    |                       Reply required                          |
    +-------------------------------+-------------------------------+

    The receiving server's IP address and port do not need to be filled
    in if the message is being multicasted.

    'Reply_required' flag shall be set to 0x1 if response to this
    message is required, otherwise set to 0x0.


3.3 PEER_NAME_TABLE_REQUEST message

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |

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    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+
    |                       Type = 0x102                            |
    +-------------------------------+-------------------------------+
    |                 sending server's IP address                   |
    +-------------------------------+-------------------------------+
    |       sender's SCTP port      |         padding               |
    +-------------------------------+-------------------------------+
    |                receiving server's IP address                  |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+
    |                      Table type = (see below)                 |
    +-------------------------------+-------------------------------+

    Note, the receiver's IP address and port do not need to be filled in
    if the message is being multicasted.

    The requested 'Table type' shall take one of the following values:

    0x1 --- HOME_LIST: PEs owned by the receiver server.
    0x2 --- REMOTE_LIST: PEs NOT owned by the receiver
            server.


3.4 PEER_NAME_TABLE_RESPONSE message

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |
    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+
    |                       Type = 0x103                            |
    +-------------------------------+-------------------------------+
    |                     sender's IP address                       |
    +-------------------------------+-------------------------------+
    |      sender's SCTP port       |         padding               |
    +-------------------------------+-------------------------------+
    |                     receiver's IP address                     |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+
    |                    Table type = (see below)                   |
    +-------------------------------+-------------------------------+
    |                  More to send = (see below)                   |
    +-------------------------------+-------------------------------+
    |                     number of pool names = n                  |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                     Pool entry #1 (see below)                 |
    |                                                               |

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    +-------------------------------+-------------------------------+
    /                                                               /
    \                                                               \
    /                                                               /
    +-------------------------------+-------------------------------+
    |                                                               |
    |                     Pool entry #n (see below)                 |
    |                                                               |
    +-------------------------------+-------------------------------+


    Field 'Table type' shall take one of the following values:

    0x1 --- HOME_LIST: PEs owned by the sending ENRP server.
    0x2 --- REMOTE_LIST: PEs NOT owned by the sending ENRP
            server.

    Field 'More to send' flag shall be set to 0x1 if there are more pool
    entries to be sent for the requested table type. Otherwise, it shall
    be set to 0x0.

    Each 'Pool entry' represents an existing pool and shall consist of
    the following:

    +-------------------------------+-------------------------------+
    |                                                               |
    |                      Pool handle name (32)                    |
    |                                                               |
    +-------------------------------+-------------------------------+
    |                      number of PEs  = m                       |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                            PE #1 (40)                         |
    |                                                               |
    +-------------------------------+-------------------------------+
    /                                                               /
    \                             .....                             \
    /                                                               /
    +-------------------------------+-------------------------------+
    |                                                               |
    |                            PE #m (40)                         |
    |                                                               |
    +-------------------------------+-------------------------------+


3.5 PEER_NAME_UPDATE message

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |
    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+

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    |                       Type = 0x104                            |
    +-------------------------------+-------------------------------+
    |                     sender's IP address                       |
    +-------------------------------+-------------------------------+
    |      sender's SCTP port       |         padding               |
    +-------------------------------+-------------------------------+
    |                    receiver's IP address                      |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                     Pool handle name (32)                     |
    |                                                               |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                         PE entry (40)                         |
    |                                                               |
    +-------------------------------+-------------------------------+
    |                 Update action (see below)                     |
    +-------------------------------+-------------------------------+

    The receiver's IP address and port do not need to be filled in if
    the message is being multicasted.

    Field 'Update action' shall take one of the following values:

    0x0 --- ADD_ENDPOINT: add the PE as a new member to the named pool
            in the local copy of the namespace.
    0x1 --- DELETE_ENDPOINT: delete the specified PE from the local copy
            of namespace _if_ the receiving server owns the PE.
    0x2 --- REMOVE_ENDPOINT: remove the specified PE from the local copy
            of namespace, regardless who owns the PE.
    0x3 --- UPDATE_ENDPOINT: replace the specified PE's attributes with
            the new information carried in this message.
    0x4 --- ENDPOINT_FAILURE: warn the receiver that the specified PE
            is potentially unreachable.
    0x5 --- CLAIM_ENDPOINT: inform the receiver that the sender has
            taken the ownership of the specified PE.


3.6 PEER_LIST_REQUEST message

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |
    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+
    |                       Type = 0x10b                            |
    +-------------------------------+-------------------------------+
    |                      sender's IP address                      |
    +-------------------------------+-------------------------------+
    |      sender's SCTP port       |         padding               |

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    +-------------------------------+-------------------------------+
    |                     receiver's IP address                     |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+

    The receiver's IP address and port do not need to be filled in if
    the message is being multicasted.


3.7 PEER_LIST_RESPONSE message

    This message shall contain all the peer information of the sending
    server.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |
    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+
    |                       Type = 0x10c                            |
    +-------------------------------+-------------------------------+
    |                     sender's IP address                       |
    +-------------------------------+-------------------------------+
    |      senders SCTP port        |         padding               |
    +-------------------------------+-------------------------------+
    |                    receiver's IP address                      |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+
    |                  responseIndication (see below)               |
    +-------------------------------+-------------------------------+
    |                     number of peers = n                       |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                   Peer entry 1 (see below)                    |
    |                                                               |
    +-------------------------------+-------------------------------+
    /                                                               /
    \                                                               \
    /                                                               /
    +-------------------------------+-------------------------------+
    |                                                               |
    |                   Peer entry n (see below)                    |
    |                                                               |
    +-------------------------------+-------------------------------+

    The 'responseIndication' flag shall be set to 0x2 to indicate a
    rejection to the request, and no 'Peer entry' shall be attached if
    the request is rejected.

    Otherwise, the 'responseIndication' flag shall be set to 0x1 and n

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    'Peer entries' attached.

    Each 'Peer entry' shall consist of the following fields:

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Peer's IP address                       |
    +-------------------------------+-------------------------------+
    |       Peer's SCTP port        |         padding               |
    +-------------------------------+-------------------------------+
    |                     Caretaker's IP address                    |
    +-------------------------------+-------------------------------+
    |     caretaker's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+

    The peer's IP address and port number serve as the identification of
    that peer. If the peer is inactive, its caretaker's IP address and
    port number shall be filled in. Otherwise, the caretaker IP and port
    fields shall be set to zeros.


3.8 TAKEOVER_INITIATE message

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |
    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+
    |                       Type = 0x106                            |
    +-------------------------------+-------------------------------+
    |                 sending server's IP address                   |
    +-------------------------------+-------------------------------+
    |      sender's SCTP port       |         padding               |
    +-------------------------------+-------------------------------+
    |                receiving server's IP address                  |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+
    |                   Target server's IP address                  |
    +-------------------------------+-------------------------------+
    |    Target server's SCTP port  |         padding               |
    +-------------------------------+-------------------------------+

    The receiving server's address and port do not need to be filled in
    if the message is being multicasted.

    The 'Target server's IP address and port number MUST be supplied.

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3.9 TAKEOVER_INITIATE_RESPONSE message

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |
    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+
    |                       Type = 0x107                            |
    +-------------------------------+-------------------------------+
    |                 sending server's IP address                   |
    +-------------------------------+-------------------------------+
    |      sender's SCTP port       |         padding               |
    +-------------------------------+-------------------------------+
    |                receiving server's IP address                  |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+
    |                   Target server's IP address                  |
    +-------------------------------+-------------------------------+
    |    Target server's SCTP port  |         padding               |
    +-------------------------------+-------------------------------+

    The receiving server's address and port do not need to be filled in
    if the message is being multicasted.

    The 'Target server's IP address and port number MUST be supplied.


3.10 TAKEOVER_PEER_SERVER message

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP server message identifier #1 = 0x27047729         |
    +-------------------------------+-------------------------------+
    |        ENRP server message identifier #2 = 0x53829149         |
    +-------------------------------+-------------------------------+
    |                       Type = 0x108                            |
    +-------------------------------+-------------------------------+
    |                 sending server's IP address                   |
    +-------------------------------+-------------------------------+
    |      sender's SCTP port       |         padding               |
    +-------------------------------+-------------------------------+
    |                receiving server's IP address                  |
    +-------------------------------+-------------------------------+
    |      receiver's SCTP port     |         padding               |
    +-------------------------------+-------------------------------+
    |                   Target server's IP address                  |
    +-------------------------------+-------------------------------+
    |    Target server's SCTP port  |         padding               |
    +-------------------------------+-------------------------------+

    The receiving server's address and port do not need to be filled in
    if the message is being multicasted.

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    The 'Target server's IP address and port number MUST be supplied.


3.11 SERVER_DUMP message

    This is an ENRP service/maintainance message sent from an ENRP
    service console.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP endpoint message identifier #1 = 0x18038688       |
    +-------------------------------+-------------------------------+
    |        ENRP endpoint message identifier #2 = 0x77734683       |
    +-------------------------------+-------------------------------+
    |                       Type = 0x7                              |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                    Console handle name (32)                   |
    |                                                               |
    +-------------------------------+-------------------------------+
    |                      Dump Type (see below)                    |
    +-------------------------------+-------------------------------+

    The 'Dump Type' field shall take one of the following values:

    0x0 --- HOME_LIST: dump the list of all the home PEs (i.e., PEs
            owned by the receiving server) from the local copy of the
            namespace.
    0x1 --- REMOTE_LIST: dump the list of all the remote PEs (i.e., PEs
            NOT owned by the receiving server) from the local copy of
            the namespace.
    0x2 --- PEER_LIST: dump the list of all the peers known to the
            receiving server.


3.12 SERVER_DUMP_RESPONSE message

    This is an ENRP service/maintainance message sent to an ENRP service
    console as a response to a SERVER_DUMP request.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        ENRP endpoint message identifier #1 = 0x18038688       |
    +-------------------------------+-------------------------------+
    |        ENRP endpoint message identifier #2 = 0x77734683       |
    +-------------------------------+-------------------------------+
    |                       Type = 0x8                              |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                     Console handle name (32)                  |
    |                                                               |

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    +-------------------------------+-------------------------------+
    |                      Dump Type (see below)                    |
    +-------------------------------+-------------------------------+
    |                  Number of Entries = n (see below)            |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                   Dump entry 1 (see below)                    |
    |                                                               |
    +-------------------------------+-------------------------------+
    /                                                               /
    \                                                               \
    /                                                               /
    +-------------------------------+-------------------------------+
    |                                                               |
    |                   Dump entry n (see below)                    |
    |                                                               |
    +-------------------------------+-------------------------------+

    The 'Dump Type' fields shall take the same values as defined in
    Section 3.11.

    When the 'Dump Type' is HOME_LIST or REMOTE_LIST, the 'Number of
    Entries' field shall be the number of pool entries carried in the
    message, and each 'Dump entry' field shall contain a pool entry and
    shall be defined as:

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                      Pool handle name (32)                    |
    |                                                               |
    +-------------------------------+-------------------------------+
    |                    number of PEs in pool = m                  |
    +-------------------------------+-------------------------------+
    |                                                               |
    |                           PE #1 (40)                          |
    |                                                               |
    +-------------------------------+-------------------------------+
    /                                                               /
    \                             .....                             \
    /                                                               /
    +-------------------------------+-------------------------------+
    |                                                               |
    |                           PE #m (40)                          |
    |                                                               |
    +-------------------------------+-------------------------------+

    When the 'Dump Type' is PEER_LIST, the 'Number of Entries' field
    shall be the number of peer entries carried in the message, and each
    'Dump entry' field shall contain a peer entry and shall be defined
    as:

    0                   1                   2                   3

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    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Peer's IP address                       |
    +-------------------------------+-------------------------------+
    |       Peer's SCTP port        |         padding               |
    +-------------------------------+-------------------------------+
    |                     Caretaker's IP address                    |
    +-------------------------------+-------------------------------+
    |     caretaker's SCTP port      |         padding               |
    +-------------------------------+-------------------------------+

    In a peer entry, the peer's IP address and port number serve as the
    identification of that peer. If the peer is inactive, its
    caretaker's IP address and port number shall be filled
    in. Otherwise, the caretaker IP and port fields shall be zeroed out.


4. ENRP Operation Procedures

    In this section, we discuss the procedures defined by ENRP. The
    procedures are divided into three groups, namely the basic ENRP
    operations, fault management, and control/maintenance procedures.

    Many of the Rserpool events call for message exchanges and other
    activities between both a PE and an ENRP server and the ENRP server
    and its peers. But only the message exchanges and activities between
    the ENRP server and its peers are considered within the ENRP
    protocol definition scope

    Procedures and message formats for communications between a PE and
    ENRP servers are defined in [ASAP]. However, in order to put our
    discussion in context, we will give brief description of the ASAP
    activities whenever appropreate.


4.1 Basic ENRP Operations

4.1.1 PE Registration

    ENRP server <-> PE:

    This action is part of the ASAP protocol and is defined in [ASAP].

    To register itself with the name space, a PE sends a REGISTRATION
    message over the ENRP client channel to its home ENRP server.

    In the REGISTRATION message, the PE indicates the name of the pool
    it wishes to join, its network access address(es) (e.g., a list of
    valid transport addresses with which the PE can be reached), and any
    load control information.

    The ENRP server handles the REGISTRATION message according to the
    following rules:


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    1) If the named pool does not exist in the namespace, the ENRP
    server will creates a new pool with that name in the namespace and
    add the PE to the pool as its first PE;

    2) If the named pool already exists in the namespace, but the
    requesting PE is not currently a member of the pool, ENRP server
    will add the PE as a new member to the pool;

    3) If the named pool already exists in the namespace AND the
    requesting PE is already a member of the pool, i.e., a case of
    duplicated registration, the ENRP server will acknowledge the
    registration request but will not take any further actions;

    4) The ENRP server may reject the registration due to reasons such
    as invalid values, lack of resource, etc.

    In cases 1 and 2 above, the ENRP server will also assume the
    ownership of the requesting PE.

    In all cases, the ENRP server will reply to the requesting PE with a
    REGISTRATION_RESPONSE message, and will indicate in the message body
    whether the registration is granted or rejected.

    ENRP server <-> Its peers:

    If the registration request is not a duplicate and is granted, the
    home ENRP server MUST take the namespace modification action as
    described in section 4.1.4.1. Otherwise, no message shall be
    exchanged with its peers.


4.1.2 PE De-registration

    ENRP server <-> PE:

    This action is part of the ASAP protocol and is defined in [ASAP].

    To remove itself from a pool, a PE sends a DEREGISTRATION message
    over the ENRP client channel to its home ENRP server.

    In response, the home ENRP server sends a REGISTRATION_RESPONSE
    message to the PE and indicates in the message body whether the
    request is granted or rejected.

    If the PE is the last one of the named pool, the home ENRP server
    will remove the pool from the namespace as well.

    The ENRP server may reject the de-registration request due to
    reasons such as invalid parameters, etc.

    It should be noted that de-registration does not stop the PE from
    sending or receiving messages.

    ENRP server <-> peers:

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    Once the de-registration request is granted and the PE removed from
    its local copy of the namespace, the home ENRP server MUST take the
    namespace modification action described in section 4.1.4.2.


4.1.3 Name Translation

    ENRP server <-> PE or PU:

    This action is part of the ASAP protocol and is defined in [ASAP].

    A PE or PU can use the name translation service provided by the ENRP
    server to resolve a pool name to a list of accessible transport
    addresses of existing PEs.

    This requires the PE or PU to send a NAME_REQUEST messages to its
    home ENRP server and in the NAME_REQUEST message specify the pool
    name to be translated.

    If the named pool exits in the namespace, the home ENRP server will
    send back a NAME_INFORMATION message that shall carry all
    information of the PEs currently registered under that pool
    name. This information may include the current load control policy
    of the pool, policy value of each PE, transport address(es) for each
    PE, etc.

    Otherwise, the ENRP server shall respond with a NAME_UNKNOWN
    message.

    ENRP server <-> peers:

    None.


4.1.4 Server Namespace Update

    This includes a set of update operations used by an ENRP server to
    inform its peer(s) the addition of a new PE, removal of an existing
    PE, or change of pool or PE properties, etc.


4.1.4.1 Add a New PE

    When a new PE is granted registration to the namespace, the home
    ENRP server uses this procedure to inform all its peers.

    An ENRP server shall multicast over the ENRP server channel a
    PEER_NAME_UPDATE message with the appropriate flag set to indicate
    to its peers about the addition of the new PE to the namespace.

    Upon the reception of this PEER_NAME_UPDATE message, each of the
    peer ENRP servers shall take the following actions:


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    1) If the named pool under which the new PE has been registered does
    not exist in the peer's local copy of the namespace, the peer ENRP
    server shall create the named pool in its local namespace copy and
    add the PE to it as the first PE. It then shall copy in all other
    attributes of the PE carried in the message.

    2) If the named pool already exists in the peer's local copy of the
    namespace, the peer shall add the new PE to the pool as a new PE and
    copy in all attributes of the PE carried in the message.

    3) If the named pool exists AND the PE is already a member of the
    pool in its the local copy of the namespace, the peer ENRP server
    shall take no actions.

    4) If the new PE is added to its local copy of namespace (i.e., case
    1 or 2 above), the peer ENRP server shall further check whether the
    PE is located on the same host as the peer ENRP server itself
    does. If so, the peer ENRP server shall assume the ownership of the
    PE, and take the claim ownership actions described in section
    4.1.4.5.


4.1.4.2 Forceful Removal of a PE

    This procedure is used by an ENRP server to inform its peer(s) to
    remove an existing PE, regardless of the ownership of the PE.

    The ENRP server shall multicast over the ENRP server channel a
    PEER_NAME_UPDATE message with the appropriate flag set to instruct
    its peers to forcefully remove the PE from their local copy of the
    namespace.

    On the reception of this PEER_NAME_UPDATE message, each peer ENRP
    server shall find and remove the PE from its local copy of the
    namespace regardless whether or not it has ownership on the PE.


4.1.4.3 Advisory Removal of a PE

    This operation is used by an ENRP server to instruct its peers to
    remove an existing PE on which the peer does not have an ownership.

    An ENRP server shall multicast over the ENRP server channel a
    PEER_NAME_UPDATE message with the appropriate flag set to instruct
    its peers to remove the specified PE from its local copy of the
    namespace _if_ the peer does not own the PE.

    On the reception of this PEER_NAME_UPDATE message, a peer ENRP
    server shall find and remove the PE from its local copy of the
    namespace _if_ it does not own this PE.


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4.1.4.4 Update PE Attributes

    This operation is used by an ENRP server to inform its peers to
    update the attributes of an existing PE.

    An ENRP server shall multicast over the ENRP server channel a
    PEER_NAME_UPDATE message with the appropriate flag set to instruct
    its peers to replace the attributes of an existing PE in its local
    copy of the name space.

    On the reception of this PEER_NAME_UPDATE message, a peer ENRP
    server shall replace the attributes of the existing PE with the new
    information carried in the message if the PE exists in its local
    copy of the name space. If the specified PE is not found in its
    local name space copy, the peer server shall add the PE following
    the steps 1) to 2) in Section 4.1.1.

4.1.4.5 Claim Ownership over a PE

    This operation is used by an ENRP server to claim the ownership on a
    specific PE and to inform its peers about its claim.

    ENRP server <-> PE:

    This action is part of the ASAP protocol and is defined in [ASAP].

    An ENRP server shall send an ASAP ENDPOINT_KEEP_ALIVE message to the
    PE. This message will cause the PE to adopt this ENRP server as its
    new home ENRP server (see section 4.10.3 in [ASAP]).

    ENRP server <-> Its peers:

    An ENRP server shall multicast over the ENRP server channel a
    PEER_NAME_UPDATE message with the appropriate flag set to inform its
    peers that it has taken the ownership of the specified PE.

    Upon the reception of this PEER_NAME_UPDATE message, a peer server
    shall check whether it is the current owner of the PE. If so, this
    peer server shall relinquish its ownership on that PE. Otherwise, no
    action is needed.


4.1.4.6 Report PE Communication Failure

    This operation is used by an ENRP server to warn its peers that it
    has noticed a potentially unreachable PE that the server does not
    have ownership on.

    An ENRP server shall multicast over the ENRP server channel a
    PEER_NAME_UPDATE message with the appropriate flag set to indicate
    that the specified PE is potentially unreachable.

    On the reception of this message, each peer ENRP server shall check
    whether it owns the specified PE. If it does, the peer server shall
    increase the <endpoint-report-failures> counter of the specified PE
    by 1. If the value of the <endpoint-report-failures> counter has

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    exceeded the protocol parameter Max-Endpoint-Report-Failures, the
    peer server shall remove the PE from its local namespace and take
    actions described in Section 4.1.4.3.

    If the peer server does not own the specified PE, it shall take no
    action.


4.1.5 PE Change Policy Value

    A PE can modify its load policy value at any time. Based on the
    number of PEs in the pool and the pool's load distrbution policy,
    this operation allows the PE to dynamically control its share of
    inbound messages received by the pool (also see section 4.5.2?? in
    [ASAP] for more on load control).

    ENRP server <-> PE:

    This action is part of the ASAP protocol and is defined in [ASAP].

    A PE normally sends an UPDATE_POLICY_VALUE ASAP message over the
    ENRP client channel to its home ENRP server in order to modify its
    policy value. The new policy value is always indicated in the
    message.

    Upon the reception of this UPDATE_POLICY_VALUE message, the home
    ENRP server will replace the policy value of that PE in its local
    copy of the namespace with the new value indicated in the message.

    ENRP server <-> peers:

    If the above update on its local copy of the namespace is
    successful, the home ENRP server shall take the Update PE Attributes
    actions as described in Section 4.1.4.4.


4.1.6 Server Download Namespace from a Peer Server

    This operation allows an ENRP server to request and receive a copy
    of a portion of the namespace from one of its peer ENRP servers.

    This operation is especially useful for a newly started ENRP server
    to initiate its local copy of the namespace, as well as for an
    existing ENRP server to correct namespace inconsistency found during
    its operation.

    1) An ENRP server shall first send a PEER_NAME_TABLE_REQUEST message
    directly to one of its peers. In the message, it shall indicate
    which portion of the namespace is being requested.

    2) Upon the reception of this message, the peer server shall
    initiate a download session in which the requested portion of the
    namespace shall be sent to the requesting ENRP server in one or more
    PEER_NAME_TABLE_RESPONSE messages.

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    If the sending ENRP server determines that multiple
    PEER_NAME_TABLE_RESPONSE messages are needed for the session, it
    shall set the appropriate flag in each PEER_NAME_TABLE_RESPONSE
    message to inform the receiving ENRP server whether or not the data
    in this message is the last piece of the transfer.

    3) During the downloading, every time the requesting ENRP server
    receives a PEER_NAME_TABLE_RESPONSE message, it shall transfer the
    data entries carried in the message into its local namespace
    database, and then check whether or not the data in this message is
    the last piece being transfered. If more data transfer is indicated,
    the requesting ENRP server shall send another
    PEER_NAME_TABLE_REQUEST message to the same peer to request for the
    next piece whenever it is ready.

    When unpacking the data entries from a PEER_NAME_TABLE_RESPONSE
    message into its local namespace database, the requesting ENRP
    server shall follow the same procedures as described in section
    2.1.1.4.1 when parsing through the PEs carrying in the message one
    by one.


4.1.7 Server Monitor Peer Status

    An ENRP server shall keep a record on the status of each of its
    known peers.

    If a message of any type is received from a peer, the ENRP server
    shall update that peers status as <active>.  If a message of any
    type is received from a peer previously unknown, the ENRP server
    shall create a record for the new peer and mark the new peer as
    <active>.


4.1.8 Server Download Peer List from a Peer Server

    This operation allows an ENRP server to request from a peer server a
    copy of its internal peer list. This is useful for a new ENRP server
    to initiate its own peer list at startup.

    An ENRP server shall send a PEER_LIST_REQUEST message to a peer to
    request a copy of the peer list.

    Upon the reception of this message, the peer server shall reply with
    a PEER_LIST_RESPONSE message and include in the message body a copy
    of its peer list, consisting of all the ENRP servers known by the
    peer togather with their status.

    If the peer itself is in the process of startup, it shall response
    with a PEER_LIST_RESPONSE message but set the appropriate flag to
    indicate that it can not grant the PEER_LIST_REQUEST. In such a
    case, the requesting ENRP server shall select another peer and
    repeat the peer list request with the new peer at a later time.

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4.1.9 ENRP Server Initialization

    This section describes the steps a new ENRP server needs to take in
    order to join the other existing ENRP servers for providing the
    namespace service in the operation scope, or initiating the
    namespace service if this is the first ENRP server starting in the
    operation scope.

    1) At startup, before getting into service, the ENRP server
    (initiating server) shall multicast a PEER_PRESENCE message with
    'Reply_required' flag set over the ENRP server channel. This is to
    inform any other existing peers in the operation scope about the
    initiating peer's presence.

    2) Upon the reception of this message, a peer shall send a
    PEER_PRESENCE without 'Reply_required' flag back to the initiating
    server, in order to help the initiating server to build a peer list.

    3) If no response to its PEER_PRESENCE message are received, the
    initiating server shall assume that it is alone in the operation
    scope and shall mark the initialization process as completed. The
    initiation server shall skip the remaining steps and start to offer
    the namespace services.

    4) If there are responses to its PEER_PRESENCE message, the
    initiating server shall then take the actions described in 4.1.8 to
    request a peer list from one of the peers that have responded.

    5) Upon the reception of the PEER_LIST_RESPONSE message from the
    peer, the initiating server shall use the information carried in the
    message to build a complete peer list, including both active and
    inactive peers in the operation scope.

    6) Then, the initiating server shall download the HOME_LIST of the
    namespace from each active peer, as described in 4.1.6.

    Moreover, the initiating server shall also pick one of the active
    peers and request to download the REMOTE_LIST from that peer.

    These downloads once done should allow the initiating server to
    create a complete view of the current namespace.

    At this point, the initialization process is completed and the
    initiating server shall start to provide namespace services.


4.2 Fault Management Operations

    The following operations are used to detect and recover from various
    system faults.



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4.2.1 Detect and Report Unreachable PE

    Two mechanisms exist to detect and report an unreachable PE:

    1) Home ENRP server periodic sanity check

    An ENRP server shall send, in every <Endpoint-sanity-cycle> seconds,
    an ENDPOINT_KEEP_ALIVE message to each of the PE it owns, and shall
    keep the number of consecutive failed send attempts in the counter
    <Endpoint-sanity-failures> of that PE.

    If the value of <Endpoint-sanity-failures> of a PE exceeds the
    pre-set threshold Max-endpoint-sanity-failures, the home ENRP
    server shall remove the PE from its local copy of the namespace
    and take the actions described in section 4.1.4.3 to inform its
    peers.

    The definition and handling of the ENDPOINT_KEEP_ALIVE message by
    the PE are part of ASAP and are described in sections 3.9?? and
    4.10.3?? in [ASAP].

 2) Failure report by peer PE

    Whenever a PE finds a peer PE unreachable (e.g., via an SCTP
    SEND.FAILURE Notification, see section 10.2 of [RFC2960]), the
    former shall send an ENDPOINT_UNREACHABLE message over the ENRP
    client channel to its home ENRP server. The message shall contain
    one of the transport addresses of the unreachable peer PE and have
    the 'Severity' flag set to NORMAL_REPORT in the message.

    The definition and procedure of ENDPOINT_UNREACHABLE message are
    part of ASAP and are described in [ASAP].

    Upon the reception of the ENDPOINT_UNREACHABLE message, the home
    ENRP server shall first check whether it owns the unreachable
    PE. If not, the home ENRP server shall take the actions described
    in section 4.1.4.6.

    If the home ENRP server does own the unreachable PE, it shall
    increase an <Endpoint-report-failures> counter of the unreachable
    PE by 1, and if the value of the <Endpoint-report-failures>
    counter exceeds threshold Max-endpoint-report-failures, the server
    shall remove the PE from its local copy of the namespace and take
    actions described in 4.1.4.3.


4.2.2 ENRP Server Failure Detection by Heartbeat

    An ENRP server shall multicast, in every <Peer-heartbeat-cycle>
    seconds, a PEER_PRESENCE message over the ENRP server channel to
    inform its peers that it is still operational. In the PEER_PRESENCE
    message, the sending ENRP server shall unset the 'Replay_required'
    flag to indicate that no response is required.


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    Occassionally, an ENRP server may also send a point-to-point
    PEER_PRESENCE message to a specific peer server, with the
    'Replay_required' flag set in the message, indicating that a
    response is required. In such a case, the receiving peer server MUST
    immediately respond to the sender with its own point-to-point
    PEER_PRESENCE message without setting the 'Replay_required' flag.


4.2.3 PE or PU Home ENRP Server Hunt

    This action is part of ASAP protocol and is defined in [ASAP].

    At its startup, or when it fails to send to (i.e., timed-out on a
    service request) with its current home ENRP server, a PE or PU shall
    initiate the following home server hunt procedure.

    In the home server hunt procedure, the PE or PU shall multicast a
    SERVER_HUNT message over the ENRP client channel, and shall repeat
    sending this message every <Timeout-server-hunt> seconds until a
    SERVER_HUNT_RESPONSE message is received from an ENRP
    server. Moreover, each time the 'Timeout-server-hunt' timer expires
    the criticality should be raised (initially criticality should be
    set to LOW_CRITICALITY).

    Then the PE or PU shall pick one of the ENRP servers that have
    responded as its new home ENRP server, and send all its subsequent
    the namespace service requests to it.

    Upon the reception of the SERVER_HUNT message, an ENRP server shall
    normally reply to the PE with a SERVER_HUNT_RESPONSE message, unless
    its peer status information indicates that there is a caretaker ENRP
    server other than itself for the node where the PE resides, AND the
    criticality flag in the SERVER_HUNT message is not HIGH_CRITICALITY.


4.2.4 ENRP Server Detecting and Taking-over Inactive Peer

    An ENRP server shall keep track the time when the last message
    (multicast or point-to-point) was received from each known peer.

    If a peer has not been heard for more than Max-time-last-heard, the
    ENRP server shall send a point-to-point PEER_PRESENCE with 'Reply
    request' to that peer.

    If the send fails or the peer does not reply after
    Max-time-no-response seconds, the ENRP server shall initiate the
    following server take-over procedures:

    1) Initiate Server Take-over Arbitration

    The ENRP server (the initiating server) shall initiate a take-over
    arbitration on the inactive peer (the target server) by multicasting
    a TAKEOVER_INITIATE message over the ENRP server channel. In the
    message, the initiating server shall specify the identification of

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    the target server.

    After multicasting the TAKEOVER_INITIATE message, the initiating
    server shall wait for a TAKEOVER_INITIATE_RESPONSE message from
    each of its active peers.

    Upon the reception of this message, other peer servers shall take
    the following actions accordingly:

    A1) If the peer server finds that itself is the target server
        indicated in the TAKEOVER_INITIATE message, it MUST
        immediately multicast a PEER_PRESENCE message over the ENRP
        server channel in an attempt to stop the take-over process.

    A2) If the peer server finds that itself has also initiated a
        take-over process on the same target server AND its IP address
        is smaller in value than that of the sender of the
        TAKEOVER_INITIATE message, the peer server shall abort its own
        take-over process and perform A3) below.

    A3) Peers other than the target peer and the initiating peer shall
        mark the target server as <inactive> and mark the initiating
        server as the caretaker of the target server and reply to the
        initiating server with a TAKEOVER_INITIATE_RESPONSE message.

    A4) Once it has received TAKEOVER_INITIATE_RESPONSE message from
        all of its active peers, the initiating server shall consider
        it won the arbitration and shall then take the actions in 2)
        below so as to complete the take-over.

        However, if it receives a PEER_PRESENCE from the target server
        at any point of the take-over, the initiating server shall
        immediately abort the take-over process and re-mark the target
        server as <active>.

    2) Take-over the target peer server

    The initiating ENRP server shall multicast a TAKEOVER_PEER_SERVER
    message over the ENRP server channel in order to inform all its
    peers about the take-over.

    In the message, identification of the inactive peer server targeted
    for the take-over MUST be included.

    The initiating server shall mark the target server as <inactive> and
    mark itself as the caretaker of the target server in its own peer
    list.

    Then it shall claim ownership on each of the PEs in its local copy
    of the namespace that is originally owned by the target server. The
    procedures in x.x.x.x. shall be followed when claiming the ownership
    of the PEs.

    The server shall finally check whether there are any inactive peers

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    (other than the current target server) which has designated the
    target server as their caretaker. If so, the initiating server shall
    perform the above ownership take-over procedure on each one of those
    inactive peers as well.


4.2.5 Registration of Remote PEs

    When an ENRP server receives a REGISTRATION message from a PE
    located on a remote machine, it shall always accept and grant the
    registration and assume ownership of the PE.

    However, if the ENRP server's peer status information indicates that
    the peer on the remote machine is inactive AND a caretaker other
    than the ENRP server itself exists for that machine, the ENRP server
    shall reject the registration and take no further actions.

    If the ENRP server has no record about a peer on that remote node,
    it shall grant the registration as above AND then create a peer
    record in its local peer list about that node, mark the new peer as
    inactive, and initiate a take-over procedure on the new peer, as
    described in section 4.2.4.


4.3 Maintenance Operations

    The following operations are used by an ENRP maintenance client to
    monitor the name space data and perform maintenances on ENRP servers
    in an operation scope.


4.3.1 Forceful Removal of a PE

    In order to force the removal of PE from the namespace, a
    maintenance client shall send an ENDPOINT_UNREACHABLE message to an
    existing ENRP server, and in the message shall indicate one of the
    transport addresses of the target PE and have the 'Severity' flag
    set to FINAL_REPORT.

    Upon the reception of this message, the ENRP server shall
    immediately remove the target PE from its local copy of the
    namespace and take actions described in Section 4.1.4.2 to inform
    its peers to do the same.


4.3.2 Dump Home PE List

    To require a copy of the information on all the PEs owned by an ENRP
    server, a maintenance client shall send a SERVER_DUMP message with
    'Dump type' flag set to HOME_LIST to the server.

    Upon receiving this message, the ENRP server shall response with a
    SERVER_DUMP_RESPONSE message with the 'Dump type' flag set to
    HOME_LIST to the maintenance client, and in the message body,

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    include information on all the PEs the server currently owns.


4.3.3 Dump Remote PE List

    To require a copy of the information on all the PEs NOT owned by an
    ENRP server, a maintenance client shall send a SERVER_DUMP message
    with 'Dump type' flag set to REMOTE_LIST to the server.

    Upon receiving this message, the server shall response with a
    SERVER_DUMP_RESPONSE message with the 'Dump type' flag set to
    REMOTE_LIST to the maintenance client, and in the message body,
    include information on all the PEs the server currently does NOT
    own.


4.3.4 Dump Peer Server List

    To require a copy of the peer list known to a specific ENRP server
    (this list most likely will also represent ALL the active and
    inactive ENPR servers in the operation scope), a maintenance client
    shall send a SERVER_DUMP message with the 'Dump type' flag set to
    PEER_SERVER_LIST to the ENRP server.

    Upon receiving this message, the server shall response with a
    SERVER_DUMP_RESPONSE message with the 'Dump type' flag set to
    PEER_SERVER_LIST to the maintenance client, and in the message body,
    include information on all the peers that server currently knows.


5.  Variables, Time Constants, and Thresholds

    The following is a summary of the variables, time values, and
    pre-set thresholds used in ASAP and ENRP protocol.


5.1 Variables

    Endpoint-report-failures --- per registered PE, this keeps the
    number of unreachable reports concerning the PE.

    Endpoint-sanity-failures --- per registered PE; this keeps the
    number of failed sanity message send attempts concerning the PE.

    Peer-server-last-heard --- per peer ENRP server; this is a time
    stamp on when the last message was received from this peer server.


5.2 Timer Constants

    Endpoint-sanity-cycle --- the period for a home ENRP server to start
    a new round of PE sanity check.

    Peer-heartbeat-cycle ---the period for an ENRP server to send out a

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    heartheat message to its known peers.


5.3 Thresholds

    Max-endpoint-sanity-failures --- pre-set threshold for
    Endpoint-sanity-failures.

    Max-endpoint-report-failures --- pre-set threshold for
    Endpoint-report-failures.

    Max-time-last-heard --- pre-set threshold for
    Peer-server-last-heard.

    Max-time-no-response --- pre-set threshold for a peer server to
    answer a PEER_PRESENCE message with reply required.

    Timeout-server-hunt --- pre-set threshold for how long a PE will
    wait for the REGISTRATION_RESPONSE from its home ENRP server.


6. References

    [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
    3", BCP 9, RFC 2026, October 1996.

    [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
    Requirement Levels", BCP 14, RFC 2119, March 1997.

    [ASAP] R. R. Stewart, Q. Xie: "Aggregate Server Access Protocol
    (ASAP)", <draft-ietf-rserpool-asap-00.txt>, work in progress.

    [RSERPOOL1] M. Tuexen, Q. Xie, R. R. Stewart, E. Lear, M. Shore,
    L. Ong, J. Loughney, M. Stillman: "Requirements for Reliable Server
    Pooling," <draft-ietf-rserpool-reqts-03.txt>, work in progress.

    [RSERPOOL2] M. Tuexen, Q. Xie, R. R. Stewart, E. Lear, M. Shore,
    L. Ong, J. Loughney, M. Stillman: "Architecture for Reliable Server
    Pooling," <draft-ietf-rserpool-arch-00.txt>, work in progress.

    [RFC2960] R. R. Stewart, Q. Xie, K. Morneault, C. Sharp,
    H. J. Schwarzbauer, T. Taylor, I. Rytina, M. Kalla, L. Zhang, and,
    V. Paxson: "Stream Control Transmission Protocol," RFC 2960, October
    2000.


7. Acknowledgements

   The authors wish to thank John Loughney, Lyndon Ong, and
   Maureen Stillman and many others for their invaluable comments.

8.  Authors' Addresses

   Randall R. Stewart

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Internet Draft        Endpoint Name Resoluton Protocol         June 2001

   24 Burning Bush Trail.
   Crystal Lake, IL 60012
   USA

   Phone: +1-815-477-2127
   EMail: rrs@cisco.com


   Qiaobing Xie
   Motorola, Inc.
   1501 W. Shure Drive, #2309
   Arlington Heights, IL 60004
   USA

   Phone: +1-847-632-3028
   EMail: qxie1@email.mot.com



                     Expires in six months from June 2001



































Xie, Stewart                                                   [Page 28]


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