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RFC 1002

 
 
 

Protocol standard for a NetBIOS service on a TCP/UDP transport: Detailed specifications

Part 2 of 3, p. 29 to 66
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4.3.  SESSION SERVICE PACKETS

4.3.1.  GENERAL FORMAT OF SESSION PACKETS

   All session service messages are sent over a TCP connection.

   All session packets are of the following general structure:

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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     |     FLAGS     |            LENGTH             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   /               TRAILER (Packet Type Dependent)                 /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The TYPE, FLAGS, and LENGTH fields are present in every session
   packet.

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   The LENGTH field is the number of bytes following the LENGTH
   field.  In other words, LENGTH is the combined size of the
   TRAILER field(s).  For example, the POSITIVE SESSION RESPONSE
   packet always has a LENGTH field value of zero (0000) while the
   RETARGET SESSION RESPONSE always has a LENGTH field value of six
   (0006).

   One of the bits of the FLAGS field acts as an additional, high-
   order bit for the LENGTH field.  Thus the cumulative size of the
   trailer field(s) may range from 0 to 128K bytes.

   Session Packet Types (in hexidecimal):

           00 -  SESSION MESSAGE
           81 -  SESSION REQUEST
           82 -  POSITIVE SESSION RESPONSE
           83 -  NEGATIVE SESSION RESPONSE
           84 -  RETARGET SESSION RESPONSE
           85 -  SESSION KEEP ALIVE

   Bit definitions of the FLAGS field:

     0   1   2   3   4   5   6   7
   +---+---+---+---+---+---+---+---+
   | 0 | 0 | 0 | 0 | 0 | 0 | 0 | E |
   +---+---+---+---+---+---+---+---+

   Symbol     Bit(s)   Description

   E               7   Length extension, used as an additional,
                       high-order bit on the LENGTH field.

   RESERVED      0-6   Reserved, must be zero (0)

4.3.2.  SESSION REQUEST PACKET

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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     |     FLAGS     |            LENGTH             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   /                          CALLED NAME                          /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   /                          CALLING NAME                         /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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4.3.3.  POSITIVE SESSION RESPONSE PACKET

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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     |     FLAGS     |            LENGTH             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.3.4.  NEGATIVE SESSION RESPONSE PACKET

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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     |     FLAGS     |            LENGTH             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   ERROR_CODE  |
   +-+-+-+-+-+-+-+-+

   NEGATIVE SESSION RESPONSE packet error code values (in
   hexidecimal):

           80 -  Not listening on called name
           81 -  Not listening for calling name
           82 -  Called name not present
           83 -  Called name present, but insufficient resources
           8F -  Unspecified error

4.3.5.  SESSION RETARGET RESPONSE PACKET

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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     |     FLAGS     |            LENGTH             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      RETARGET_IP_ADDRESS                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           PORT                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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4.3.6.  SESSION MESSAGE PACKET

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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     |     FLAGS     |            LENGTH             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   /                                                               /
   /                           USER_DATA                           /
   /                                                               /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.3.7.  SESSION KEEP ALIVE PACKET

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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     |     FLAGS     |            LENGTH             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.4.  DATAGRAM SERVICE PACKETS

4.4.1.  NetBIOS DATAGRAM HEADER

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   MSG_TYPE    |     FLAGS     |           DGM_ID              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           SOURCE_IP                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          SOURCE_PORT          |          DGM_LENGTH           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         PACKET_OFFSET         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   MSG_TYPE values (in hexidecimal):

           10 -  DIRECT_UNIQUE DATAGRAM
           11 -  DIRECT_GROUP DATAGRAM
           12 -  BROADCAST DATAGRAM
           13 -  DATAGRAM ERROR
           14 -  DATAGRAM QUERY REQUEST
           15 -  DATAGRAM POSITIVE QUERY RESPONSE
           16 -  DATAGRAM NEGATIVE QUERY RESPONSE

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   Bit definitions of the FLAGS field:

     0   1   2   3   4   5   6   7
   +---+---+---+---+---+---+---+---+
   | 0 | 0 | 0 | 0 |  SNT  | F | M |
   +---+---+---+---+---+---+---+---+

   Symbol     Bit(s)   Description

   M               7   MORE flag, If set then more NetBIOS datagram
                       fragments follow.

   F               6   FIRST packet flag,  If set then this is first
                       (and possibly only) fragment of NetBIOS
                       datagram

   SNT           4,5   Source End-Node type:
                          00 = B node
                          01 = P node
                          10 = M node
                          11 = NBDD
   RESERVED      0-3   Reserved, must be zero (0)

4.4.2.  DIRECT_UNIQUE, DIRECT_GROUP, & BROADCAST DATAGRAM

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   MSG_TYPE    |     FLAGS     |           DGM_ID              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           SOURCE_IP                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          SOURCE_PORT          |          DGM_LENGTH           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         PACKET_OFFSET         |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   /                          SOURCE_NAME                          /
   /                                                               /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   /                       DESTINATION_NAME                        /
   /                                                               /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   /                           USER_DATA                           /
   /                                                               /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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4.4.3.  DATAGRAM ERROR PACKET

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   MSG_TYPE    |     FLAGS     |           DGM_ID              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           SOURCE_IP                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          SOURCE_PORT          |  ERROR_CODE   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ERROR_CODE values (in hexidecimal):

           82 -  DESTINATION NAME NOT PRESENT
           83 -  INVALID SOURCE NAME FORMAT
           84 -  INVALID DESTINATION NAME FORMAT

4.4.4.  DATAGRAM QUERY REQUEST

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   MSG_TYPE    |     FLAGS     |           DGM_ID              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           SOURCE_IP                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          SOURCE_PORT          |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   /                       DESTINATION_NAME                        /
   /                                                               /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.4.5.  DATAGRAM POSITIVE AND NEGATIVE QUERY RESPONSE

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   MSG_TYPE    |     FLAGS     |           DGM_ID              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           SOURCE_IP                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          SOURCE_PORT          |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   /                       DESTINATION_NAME                        /
   /                                                               /
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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5.  PROTOCOL DESCRIPTIONS

5.1.  NAME SERVICE PROTOCOLS

   A REQUEST packet is always sent to the well known UDP port -
   NAME_SERVICE_UDP_PORT.  The destination address is normally
   either the IP broadcast address or the address of the NBNS - the
   address of the NBNS server it set up at initialization time.  In
   rare cases, a request packet will be sent to an end node, e.g.  a
   NAME QUERY REQUEST sent to "challenge" a node.

   A RESPONSE packet is always sent to the source UDP port and
   source IP address of the request packet.

   A DEMAND packet must always be sent to the well known UDP port -
   NAME_SERVICE_UDP_PORT.  There is no restriction on the target IP
   address.

   Terms used in this section:

   tid -            Transaction ID.  This is a value composed from
                    the requestor's IP address and a unique 16 bit
                    value generated by the originator of the
                    transaction.

5.1.1.  B-NODE ACTIVITY

5.1.1.1.  B-NODE ADD NAME

   PROCEDURE add_name(newname)

   /*
    * Host initiated processing for a B node
    */
   BEGIN

        REPEAT

             /* build name service packet */

             ONT = B_NODE; /* broadcast node */
             G = UNIQUE;   /* unique name */
             TTL = 0;

             broadcast NAME REGISTRATION REQUEST packet;

             /*
              * remote node(s) will send response packet
              * if applicable
              */

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             pause(BCAST_REQ_RETRY_TIMEOUT);

        UNTIL response packet is received or
             retransmit count has been exceeded

        IF no response packet was received THEN
        BEGIN /* no response */
             /*
              * build packet
              */

             ONT = B_NODE; /* broadcast node */
             G = UNIQUE;   /* unique name */
             TTL = 0;

             /*
              * Let other nodes known you have the name
              */

             broadcast NAME UPDATE REQUEST packet;
             /* name can be added to local name table */
             return success;
        END /* no response */
        ELSE
        BEGIN /* got response */

             /*
              * Match return transaction id
              * against tid sent in request
              */

            IF NOT response tid = request tid THEN
            BEGIN
             ignore response packet;
            END
            ELSE
            CASE packet type OF

            NEGATIVE NAME REGISTRATION RESPONSE:

                 return failure; /* name cannot be added */

            POSITIVE NAME REGISTRATION RESPONSE:
            END-NODE CHALLENGE NAME REGISTRATION RESPONSE:

                 /*
                  * B nodes should normally not get this
                  * response.
                  */

                  ignore packet;

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            END /* case */;
        END /* got response */
   END /* procedure */

5.1.1.2.  B-NODE ADD_GROUP NAME

   PROCEDURE add_group_name(newname)

   /*
    * Host initiated processing for a B node
    */

   BEGIN
        /*
         * same as for a unique name with the
         * exception that the group bit (G) must
         * be set in the request packets.
         */

        ...
        G = GROUP;
        ...
        ...

        /*
         * broadcast request ...
         */


   END

5.1.1.3.  B-NODE FIND_NAME

   PROCEDURE find_name(name)

   /*
    * Host initiated processing for a B node
    */

   BEGIN

        REPEAT
             /*
              * build packet
              */
             ONT = B;
             TTL = 0;
             G = DONT CARE;

             broadcast NAME QUERY REQUEST packet;

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             /*
              * a node might send response packet
              */

             pause(BCAST_REQ_RETRY_TIMEOUT);
        UNTIL response packet received OR
             max transmit threshold exceeded

        IF no response packet received THEN
             return failure;
        ELSE
        IF NOT response tid = request tid THEN
             ignore packet;
        ELSE
        CASE packet type OF
        POSITIVE NAME QUERY RESPONSE:
             /*
              * Start a timer to detect conflict.
              *
              * Be prepared to detect conflict if
              * any more response packets are received.
              *
              */

             save response as authoritative response;
             start_timer(CONFLICT_TIMER);
             return success;

        NEGATIVE NAME QUERY RESPONSE:
        REDIRECT NAME QUERY RESPONSE:

             /*
              * B Node should normally not get either
              * response.
              */

              ignore response packet;

        END /* case */
   END /* procedure */

5.1.1.4.  B NODE NAME RELEASE

   PROCEDURE delete_name (name)
   BEGIN

        REPEAT

             /*
              * build packet
              */

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             ...

             /*
              * send request
              */

             broadcast NAME RELEASE REQUEST packet;

             /*
              * no response packet expected
              */

             pause(BCAST_REQ_RETRY_TIMEOUT);

        UNTIL retransmit count has been exceeded
   END /* procedure */

5.1.1.5.  B-NODE INCOMING PACKET PROCESSING

   Following processing is done when broadcast or unicast packets
   are received at the NAME_SERVICE_UDP_PORT.

   PROCEDURE process_incoming_packet(packet)

   /*
    * Processing initiated by incoming packets for a B node
    */

   BEGIN
        /*
         * Note: response packets are always sent
         * to:
         * source IP address of request packet
         * source UDP port of request packet
         */

        CASE packet type OF

        NAME REGISTRATION REQUEST (UNIQUE):
             IF name exists in local name table THEN
                  send NEGATIVE NAME REGISTRATION RESPONSE ;
        NAME REGISTRATION REQUEST (GROUP):
             IF name exists in local name table THEN
             BEGIN
                  IF local entry is a unique name THEN
                      send NEGATIVE NAME REGISTRATION RESPONSE ;
             END
        NAME QUERY REQUEST:
             IF name exists in local name table THEN
             BEGIN
                  build response packet;

Top      Up      ToC       Page 40 
                  send POSITIVE NAME QUERY RESPONSE;
        POSITIVE NAME QUERY RESPONSE:
             IF name conflict timer is not active THEN
             BEGIN
                  /*
                   * timer has expired already...  ignore this
                   * packet
                   */

                  return;
             END
             ELSE /* timer is active */
             IF a response for this name has previously been
                  received THEN
             BEGIN /* existing entry */

                  /*
                   * we sent out a request packet, and
                   * have already received (at least)
                   * one response
                   *
                   * Check if conflict exists.
                   * If so, send out a conflict packet.
                   *
                   * Note: detecting conflict does NOT
                   * affect any existing sessions.
                   *
                   */

                  /*
                   * Check for name conflict.
                   * See "Name Conflict" in Concepts and Methods
                   */
                  check saved authoritative response against
                       information in this response packet;
                  IF conflict detected THEN
                  BEGIN
                       unicast NAME CONFLICT DEMAND packet;
                       IF entry exists in cache THEN
                       BEGIN
                            remove entry from cache;
                       END
                  END
             END /* existing entry */
             ELSE
             BEGIN
                  /*
                   * Note: If this was the first response
                   * to a name query, it would have been
                   * handled in the
                   * find_name() procedure.

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                   */

                  ignore packet;
             END
        NAME CONFLICT DEMAND:
             IF name exists in local name table THEN
             BEGIN
                  mark name as conflict detected;

                  /*
                   * a name in the state "conflict detected"
                   * does not "logically" exist on that node.
                   * No further session will be accepted on
                   * that name.
                   * No datagrams can be sent against that name.
                   * Such an entry will not be used for
                   * purposes of processing incoming request
                   * packets.
                   * The only valid user NetBIOS operation
                   * against such a name is DELETE NAME.
                   */
             END
        NAME RELEASE REQUEST:
             IF caching is being done THEN
             BEGIN
                  remove entry from cache;
             END
        NAME UPDATE REQUEST:
             IF caching is being done THEN
             BEGIN
                  IF entry exists in cache already,
                       update cache;
                  ELSE IF name is "interesting" THEN
                  BEGIN
                       add entry to cache;
                  END
             END

        NODE STATUS REQUEST:
             IF name exists in local name table THEN
             BEGIN
                  /*
                   * send only those names that are
                   * in the same scope as the scope
                   * field in the request packet
                   */

                  send NODE STATUS RESPONSE;
             END
   END

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5.1.2.  P-NODE ACTIVITY

   All packets sent or received by P nodes are unicast UDP packets.
   A P node sends name service requests to the NBNS node that is
   specified in the P-node configuration.

5.1.2.1.  P-NODE ADD_NAME

   PROCEDURE add_name(newname)

   /*
    * Host initiated processing for a P node
    */

   BEGIN

        REPEAT
             /*
              * build packet
              */

             ONT = P;
             G = UNIQUE;
             ...

             /*
              * send request
              */

             unicast NAME REGISTRATION REQUEST packet;

             /*
              * NBNS will send response packet
              */

             IF receive a WACK RESPONSE THEN
                  pause(time from TTL field of response);
             ELSE
                  pause(UCAST_REQ_RETRY_TIMEOUT);
        UNTIL response packet is received OR
             retransmit count has been exceeded

        IF no response packet was received THEN
        BEGIN /* no response */
             /*
              * NBNS is down.  Cannot claim name.
              */

             return failure; /* name cannot be claimed */
        END /* no response */
        ELSE

Top      Up      ToC       Page 43 
        BEGIN /* response */
            IF NOT response tid = request tid THEN
            BEGIN
             /*  Packet may belong to another transaction  */
             ignore response packet;
            END
            ELSE
            CASE packet type OF

            POSITIVE NAME REGISTRATION RESPONSE:

                 /*
                  * name can be added
                  */

                 adjust refresh timeout value, TTL, for this name;
                 return success;      /* name can be added */

            NEGATIVE NAME REGISTRATION RESPONSE:
                 return failure; /* name cannot be added */

            END-NODE CHALLENGE REGISTRATION REQUEST:
            BEGIN /* end node challenge */

                 /*
                  * The response packet has in it the
                  * address of the presumed owner of the
                  * name.  Challenge that owner.
                  * If owner either does not
                  * respond or indicates that he no longer
                  * owns the name, claim the name.
                  * Otherwise, the name cannot be claimed.
                  *
                  */

                 REPEAT
                  /*
                   * build packet
                   */
                  ...

                  unicast NAME QUERY REQUEST packet to the
                       address contained in the END NODE
                       CHALLENGE RESPONSE packet;

                  /*
                   * remote node may send response packet
                   */

                  pause(UCAST_REQ_RETRY_TIMEOUT);

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                 UNTIL response packet is received or
                     retransmit count has been exceeded
                 IF no response packet is received OR
                       NEGATIVE NAME QUERY RESPONSE packet
                       received THEN
                 BEGIN /* update */

                  /*
                   * name can be claimed
                   */

                  REPEAT

                      /*
                       * build packet
                       */
                       ...

                      unicast NAME UPDATE REQUEST to NBNS;

                      /*
                       * NBNS node will send response packet
                       */

                      IF receive a WACK RESPONSE THEN
                            pause(time from TTL field of response);
                      ELSE
                            pause(UCAST_REQ_RETRY_TIMEOUT);
                  UNTIL response packet is received or
                      retransmit count has been exceeded
                  IF no response packet received THEN
                  BEGIN /* no response */

                       /*
                        * name could not be claimed
                        */

                       return failure;
                  END /* no response */
                  ELSE
                  CASE packet type OF
                       POSITIVE NAME REGISTRATION RESPONSE:
                            /*
                             * add name
                             */
                            return success;
                       NEGATIVE NAME REGISTRATION RESPONSE:

                            /*
                             * you lose  ...
                             */

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                            return failure;
                       END /* case */
                 END /* update */
                 ELSE

                 /*
                  * received a positive response to the "challenge"
                  * Remote node still has name
                  */

                  return failure;
            END /* end node challenge */
        END /* response */
   END /* procedure */

5.1.2.2.  P-NODE ADD GROUP NAME

   PROCEDURE add_group_name(newname)

   /*
    * Host initiated processing for a P node
    */

   BEGIN
        /*
         * same as for a unique name, except that the
         * request packet must indicate that a
         * group name claim is being made.
         */

        ...
        G = GROUP;
        ...

        /*
         * send packet
         */
         ...


   END

5.1.2.3.  P-NODE FIND NAME

   PROCEDURE find_name(name)

   /*
    * Host initiated processing for a P node
    */

   BEGIN

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        REPEAT
             /*
              * build packet
              */

             ONT = P;
             G = DONT CARE;

             unicast NAME QUERY REQUEST packet;

             /*
              * a NBNS node might send response packet
              */

             IF receive a WACK RESPONSE THEN
                  pause(time from TTL field of response);
             ELSE
                  pause(UCAST_REQ_RETRY_TIMEOUT);
        UNTIL response packet received OR
             max transmit threshold exceeded

        IF no response packet received THEN
             return failure;
        ELSE
        IF NOT response tid = request tid THEN
             ignore packet;
        ELSE
        CASE packet type OF
        POSITIVE NAME QUERY RESPONSE:
             return success;

        REDIRECT NAME QUERY RESPONSE:

             /*
              * NBNS node wants this end node
              * to use some other NBNS node
              * to resolve the query.
              */

              repeat query with NBNS address
                  in the response packet;
        NEGATIVE NAME QUERY RESPONSE:
             return failure;

        END /* case */
   END /* procedure */

5.1.2.4.  P-NODE DELETE_NAME

   PROCEDURE delete_name (name)

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   /*
    * Host initiated processing for a P node
    */

   BEGIN

        REPEAT

             /*
              * build packet
              */
             ...

             /*
              * send request
              */

             unicast NAME RELEASE REQUEST packet;
             IF receive a WACK RESPONSE THEN
                  pause(time from TTL field of response);
             ELSE
                  pause(UCAST_REQ_RETRY_TIMEOUT);
        UNTIL retransmit count has been exceeded
             or response been received

        IF response has been received THEN
        CASE packet type OF
        POSITIVE NAME RELEASE RESPONSE:
             return success;
        NEGATIVE NAME RELEASE RESPONSE:

             /*
              * NBNS does want node to delete this
              * name !!!
              */

             return failure;
        END /* case */
   END /* procedure */

5.1.2.5.  P-NODE INCOMING PACKET PROCESSING

   Processing initiated by reception of packets at a P node

   PROCEDURE process_incoming_packet(packet)

   /*
    * Processing initiated by incoming packets at a P node
    */

   BEGIN

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        /*
         * always ignore UDP broadcast packets
         */

        IF packet was sent as a broadcast THEN
        BEGIN
             ignore packet;
             return;
        END
        CASE packet type of

        NAME CONFLICT DEMAND:
             IF name exists in local name table THEN
                  mark name as in conflict;
             return;

        NAME QUERY REQUEST:
             IF name exists in local name table THEN
             BEGIN /* name exists */

                  /*
                   * build packet
                   */
                  ...

                  /*
                   * send response to the IP address and port
                   * number from which the request was received.
                   */

                  send POSITIVE NAME QUERY RESPONSE ;
                  return;
             END /* exists */
             ELSE
             BEGIN /* does not exist */

                  /*
                   * send response to the requestor
                   */

                  send NEGATIVE NAME QUERY RESPONSE ;
                  return;
             END /* does not exist */
        NODE STATUS REQUEST:
             /*
              * Name of "*" may be used for force node to
              * divulge status for administrative purposes
              */
             IF name in local name table OR name = "*" THEN
             BEGIN
                  /*

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                   * Build response packet and
                   * send to requestor node
                   * Send only those names that are
                   * in the same scope as the scope
                   * in the request packet.
                   */

                  send NODE STATUS RESPONSE;
             END

        NAME RELEASE REQUEST:
             /*
              * This will be received if the NBNS wants to flush the
              * name from the local name table, or from the local
              * cache.
              */

             IF name exists in the local name table THEN
             BEGIN
                  delete name from local name table;
                  inform user that name has been deleted;
             END
             ELSE
                  IF name has been cached locally THEN
                  BEGIN
                       remove entry from cache:
                  END

        END /* case */
   END /* procedure */

5.1.2.6.  P-NODE TIMER INITIATED PROCESSING

   Processing initiated by timer expiration.

   PROCEDURE timer_expired()
   /*
    * Processing initiated by the expiration of a timer on a P node
    */
   BEGIN
        /*
         * Send a NAME REFRESH REQUEST for each name which the
         * TTL which has expired.
         */
        REPEAT
             build NAME REFRESH REQUEST packet;
             REPEAT
                  send packet to NBNS;

                  IF receive a WACK RESPONSE THEN
                       pause(time from TTL field of response);

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                  ELSE
                       pause(UCAST_REQ_RETRY_TIMEOUT);
             UNTIL response packet is received or
                  retransmit count has been exceeded

             CASE packet type OF
               POSITIVE NAME REGISTRATION RESPONSE:
                  /* successfully refreshed */
                  reset TTL timer for this name;

               NEGATIVE NAME REGISTRATION RESPONSE:
                  /*
                   * refused, can't keep name
                   * assume in conflict
                   */
                  mark name as in conflict;
             END /* case */

        UNTIL request sent for all names for which TTL
             has expired
   END /* procedure */

5.1.3.  M-NODE ACTIVITY

   M nodes behavior is similar to that of P nodes with the addition
   of some B node-like broadcast actions.  M node name service
   proceeds in two steps:

   1.Use broadcast UDP based name service.  Depending on the
     operation, goto step 2.

   2.Use directed UDP name service.

   The following code for M nodes is exactly the same as for a P
   node, with the exception that broadcast operations are done
   before P type operation is attempted.

5.1.3.1.  M-NODE ADD NAME

   PROCEDURE add_name(newname)

   /*
    * Host initiated processing for a M node
    */

   BEGIN

        /*
         * check if name exists on the
         * broadcast area
         */

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        REPEAT
            /* build packet */

            ....
            broadcast NAME REGISTRATION REQUEST packet;
            pause(BCAST_REQ_RETRY_TIMEOUT);

        UNTIL response packet is received or
             retransmit count has been  exceeded

        IF valid response received THEN
        BEGIN
             /* cannot claim name */

             return failure;
        END

        /*
         * No objections received within the
         * broadcast area.
         * Send request to name server.
         */

        REPEAT
             /*
              * build packet
              */

             ONT = M;
             ...

             unicast NAME REGISTRATION REQUEST packet;

             /*
              * remote NBNS will send response packet
              */

             IF receive a WACK RESPONSE THEN
                  pause(time from TTL field of response);
             ELSE
                  pause(UCAST_REQ_RETRY_TIMEOUT);

        UNTIL response packet is received or
             retransmit count has been exceeded

        IF no response packet was received THEN
        BEGIN /* no response */
             /*
              * NBNS is down.  Cannot claim name.
              */

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             return failure; /* name cannot be claimed */
        END /* no response */
        ELSE
        BEGIN /* response */
            IF NOT response tid = request tid THEN
            BEGIN
             ignore response packet;
            END
            ELSE
            CASE packet type OF
            POSITIVE NAME REGISTRATION RESPONSE:

                 /*
                  * name can be added
                  */

                 adjust refresh timeout value, TTL;
                 return success;      /* name can be added */

            NEGATIVE NAME REGISTRATION RESPONSE:
                 return failure; /* name cannot be added */

            END-NODE CHALLENGE REGISTRATION REQUEST:
            BEGIN /* end node challenge */

                 /*
                  * The response packet has in it the
                  * address of the presumed owner of the
                  * name.  Challenge that owner.
                  * If owner either does not
                  * respond or indicates that he no longer
                  * owns the name, claim the name.
                  * Otherwise, the name cannot be claimed.
                  *
                  */

                 REPEAT
                  /*
                   * build packet
                   */
                  ...

                  /*
                   * send packet to address contained in the
                   * response packet
                   */

                  unicast NAME QUERY REQUEST packet;

                  /*
                   * remote node may send response packet

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                   */

                  pause(UCAST_REQ_RETRY_TIMEOUT);

                 UNTIL response packet is received or
                     retransmit count has been exceeded
                 IF no response packet is received THEN
                 BEGIN /* no response */

                  /*
                   * name can be claimed
                   */
                  REPEAT

                      /*
                       * build packet
                       */
                       ...

                      unicast NAME UPDATE REQUEST to NBNS;

                      /*
                       * NBNS node will send response packet
                       */

                      IF receive a WACK RESPONSE THEN
                            pause(time from TTL field of response);
                  ELSE
                       pause(UCAST_REQ_RETRY_TIMEOUT);

                  UNTIL response packet is received or
                      retransmit count has been exceeded
                  IF no response packet received THEN
                  BEGIN /* no response */

                       /*
                        * name could not be claimed
                        */

                       return failure;
                  END /* no response */
                  ELSE
                  CASE packet type OF
                  POSITIVE NAME REGISTRATION RESPONSE:
                       /*
                        * add name
                        */

                       return success;
                  NEGATIVE NAME REGISTRATION RESPONSE:

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                       /*
                        * you lose  ...
                        */

                       return failure;
                  END /* case */
                 END /* no response */
                 ELSE
                 IF NOT response tid = request tid THEN
                 BEGIN
                  ignore response packet;
                 END

                 /*
                  * received a response to the "challenge"
                  * packet
                  */

                 CASE packet type OF
                 POSITIVE NAME QUERY:

                  /*
                   * remote node still has name.
                   */

                  return failure;
                 NEGATIVE NAME QUERY:

                  /*
                   * remote node no longer has name
                   */

                  return success;
                 END /* case */
            END /* end node challenge */
            END /* case */
        END /* response */
   END /* procedure */

5.1.3.2.  M-NODE ADD GROUP NAME

   PROCEDURE add_group_name(newname)

   /*
    * Host initiated processing for a P node
    */

   BEGIN
        /*
         * same as for a unique name, except that the
         * request packet must indicate that a

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         * group name claim is being made.
         */

        ...
        G = GROUP;
        ...

        /*
         * send packet
         */
         ...


   END

5.1.3.3.  M-NODE FIND NAME

   PROCEDURE find_name(name)

   /*
    * Host initiated processing for a M node
    */

   BEGIN
        /*
         * check if any node on the broadcast
         * area has the name
         */

        REPEAT
             /* build packet */
             ...

             broadcast NAME QUERY REQUEST packet;
             pause(BCAST_REQ_RETRY_TIMEOUT);
        UNTIL response packet received OR
             max transmit threshold exceeded

        IF valid response received THEN
        BEGIN
             save response as authoritative response;
             start_timer(CONFLICT_TIMER);
             return success;
        END

        /*
         * no valid response on the b'cast segment.
         * Try the name server.
         */

        REPEAT

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             /*
              * build packet
              */

             ONT = M;
             G = DONT CARE;

             unicast NAME QUERY REQUEST packet to NBNS;

             /*
              * a NBNS node might send response packet
              */

             IF receive a WACK RESPONSE THEN
                  pause(time from TTL field of response);
             ELSE
                  pause(UCAST_REQ_RETRY_TIMEOUT);
        UNTIL response packet received OR
             max transmit threshold exceeded

        IF no response packet received THEN
             return failure;
        ELSE
        IF NOT response tid = request tid THEN
             ignore packet;
        ELSE
        CASE packet type OF
        POSITIVE NAME QUERY RESPONSE:
             return success;

        REDIRECT NAME QUERY RESPONSE:

             /*
              * NBNS node wants this end node
              * to use some other NBNS node
              * to resolve the query.
              */

              repeat query with NBNS address
                  in the response packet;
        NEGATIVE NAME QUERY RESPONSE:
             return failure;

        END /* case */
   END /* procedure */

5.1.3.4.  M-NODE DELETE NAME

   PROCEDURE delete_name (name)

   /*

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    * Host initiated processing for a P node
    */

   BEGIN
        /*
         * First, delete name on NBNS
         */

        REPEAT

             /*
              * build packet
              */
             ...

             /*
              * send request
              */

             unicast NAME RELEASE REQUEST packet to NBNS;

             IF receive a WACK RESPONSE THEN
                  pause(time from TTL field of response);
             ELSE
                  pause(UCAST_REQ_RETRY_TIMEOUT);
        UNTIL retransmit count has been exceeded
             or response been received

        IF response has been received THEN
        CASE packet type OF
        POSITIVE NAME RELEASE RESPONSE:
             /*
              * Deletion of name on b'cast segment is deferred
              * until after NBNS has deleted the name
              */

             REPEAT
                  /* build packet */

                  ...
                  broadcast NAME RELEASE REQUEST;
                  pause(BCAST_REQ_RETRY_TIMEOUT);
             UNTIL rexmt threshold exceeded

             return success;
        NEGATIVE NAME RELEASE RESPONSE:

             /*
              * NBNS does want node to delete this
              * name
              */

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             return failure;
        END /* case */
   END /* procedure */

5.1.3.5.  M-NODE INCOMING PACKET PROCESSING

   Processing initiated by reception of packets at a M node

   PROCEDURE process_incoming_packet(packet)

   /*
    * Processing initiated by incoming packets at a M node
    */

   BEGIN
        CASE packet type of

        NAME CONFLICT DEMAND:
             IF name exists in local name table THEN
                  mark name as in conflict;
             return;

        NAME QUERY REQUEST:
             IF name exists in local name table THEN
             BEGIN /* name exists */

                  /*
                   * build packet
                   */
                  ...

                  /*
                   * send response to the IP address and port
                   * number from which the request was received.
                   */

                  send POSITIVE NAME QUERY RESPONSE ;
                  return;
             END /* exists */
             ELSE
             BEGIN /* does not exist */

                  /*
                   * send response to the requestor
                   */

                  IF request NOT broadcast THEN
                       /*
                        * Don't send negative responses to
                        * queries sent by B nodes
                        */

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                       send NEGATIVE NAME QUERY RESPONSE ;
                  return;
             END /* does not exist */
        NODE STATUS REQUEST:
             BEGIN
             /*
              * Name of "*" may be used for force node to
              * divulge status for administrative purposes
              */
             IF name in local name table OR name = "*" THEN
                  /*
                   * Build response packet and
                   * send to requestor node
                   * Send only those names that are
                   * in the same scope as the scope
                   * in the request packet.
                   */

                  send NODE STATUS RESPONSE;
             END

        NAME RELEASE REQUEST:
             /*
              * This will be received if the NBNS wants to flush the
              * name from the local name table, or from the local
              * cache.
              */

             IF name exists in the local name table THEN
             BEGIN
                  delete name from local name table;
                  inform user that name has been deleted;
             END
             ELSE
                  IF name has been cached locally THEN
                  BEGIN
                       remove entry from cache:
                  END

        NAME REGISTRATION REQUEST (UNIQUE):
             IF name exists in local name table THEN
                  send NEGATIVE NAME REGISTRATION RESPONSE ;
        NAME REGISTRATION REQUEST (GROUP):
             IF name exists in local name table THEN
             BEGIN
                  IF local entry is a unique name THEN
                      send NEGATIVE NAME REGISTRATION RESPONSE ;
             END
        END /* case */
   END /* procedure */

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5.1.3.6.  M-NODE TIMER INITIATED PROCESSING

   Processing initiated by timer expiration:

   PROCEDURE timer_expired()
   /*
    * Processing initiated by the expiration of a timer on a M node
    */
   BEGIN
        /*
         * Send a NAME REFRESH REQUEST for each name which the
         * TTL which has expired.
         */
        REPEAT
             build NAME REFRESH REQUEST packet;
             REPEAT
                  send packet to NBNS;

                  IF receive a WACK RESPONSE THEN
                       pause(time from TTL field of response);
                  ELSE
                       pause(UCAST_REQ_RETRY_TIMEOUT);
             UNTIL response packet is received or
                  retransmit count has been exceeded

             CASE packet type OF
               POSITIVE NAME REGISTRATION RESPONSE:
                  /* successfully refreshed */
                  reset TTL timer for this name;

               NEGATIVE NAME REGISTRATION RESPONSE:
                  /*
                   * refused, can't keep name
                   * assume in conflict
                   */
                  mark name as in conflict;
             END /* case */

        UNTIL request sent for all names for which TTL
             has expired
   END /* procedure */

5.1.4.  NBNS ACTIVITY

   A NBNS node will receive directed packets from P and M nodes.
   Reply packets are always sent as directed packets to the source
   IP address and UDP port number.  Received broadcast packets must
   be ignored.

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5.1.4.1.  NBNS INCOMING PACKET PROCESSING

   PROCEDURE process_incoming_packet(packet)

   /*
    * Incoming packet processing on a NS node
    */

   BEGIN
        IF packet was sent as a broadcast THEN
        BEGIN
             discard packet;
             return;
        END
        CASE packet type of

        NAME REGISTRATION REQUEST (UNIQUE):
             IF unique name exists in data base THEN
             BEGIN /* unique name exists */
                  /*
                   * NBNS node may be a "passive"
                   * server in that it expects the
                   * end node to do the challenge
                   * server.  Such a NBNS node is
                   * called a "non-secure" server.
                   * A "secure" server will do the
                   * challenging before it sends
                   * back a response packet.
                   */

                  IF non-secure THEN
                  BEGIN
                       /*
                        * build response packet
                        */
                       ...


                       /*
                        * let end node do the challenge
                        */

                       send END-NODE CHALLENGE NAME REGISTRATION
                            RESPONSE;
                       return;
                  END
                  ELSE
                  /*
                   * secure server - do the name
                   * challenge operation
                   */

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                  REPEAT
                      send NAME QUERY REQUEST;
                      pause(UCAST_REQ_RETRY_TIMEOUT);
                  UNTIL response has been received or
                       retransmit count has been exceeded
                  IF no response was received THEN
                  BEGIN

                       /* node down */

                       update data base - remove entry;
                       update data base - add new entry;
                       send POSITIVE NAME REGISTRATION RESPONSE;
                       return;
                  END
                  ELSE
                  BEGIN /* challenged node replied */
                      /*
                       * challenged node replied with
                       * a response packet
                       */

                      CASE packet type

                      POSITIVE NAME QUERY RESPONSE:

                       /*
                        * name still owned by the
                        * challenged node
                        *
                        * build packet and send response
                        */
                        ...


                       /*
                        * Note: The NBNS will need to
                        * keep track (based on transaction id) of
                        * the IP address and port number
                        * of the original requestor.
                        */

                       send NEGATIVE NAME REGISTRATION RESPONSE;
                       return;
                      NEGATIVE NAME QUERY RESPONSE:

                       update data base - remove entry;
                       update data base - add new  entry;

                       /*
                        * build response packet and send

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                        * response
                        */
                       send POSITIVE NAME REGISTRATION RESPONSE;
                       return;
                      END /* case */
                  END /* challenged node replied */
             END /* unique name exists in data base */
             ELSE
             IF group name exists in data base THEN
             BEGIN /* group names exists */

                  /*
                   * Members of a group name are NOT
                   * challenged.
                   * Make the assumption that
                   * at least some of the group members
                   * are still alive.
                   * Refresh mechanism will
                   * allow the NBNS to detect when all
                   * members of a group no longer use that
                   * name
                   */

                   send NEGATIVE NAME REGISTRATION RESPONSE;
             END /* group name exists */
             ELSE
             BEGIN /* name does not exist */

                  /*
                   * Name does not exist in data base
                   *
                   * This code applies to both non-secure
                   * and secure server.
                   */

                  update data base - add new entry;
                  send POSITIVE NAME REGISTRATION RESPONSE;
                  return;
             END

        NAME QUERY REQUEST:
             IF name exists in data base THEN
             BEGIN
                  /*
                   * build response packet and send to
                   * requestor
                   */
                   ...

                  send POSITIVE NAME QUERY RESPONSE;
                  return;

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             ELSE
             BEGIN
                  /*
                   * build response packet and send to
                   * requestor
                   */
                   ...

                  send NEGATIVE NAME QUERY RESPONSE;
                  return;
             END

        NAME REGISTRATION REQUEST (GROUP):
             IF name exists in data base THEN
             BEGIN
                  IF local entry is a unique name THEN
                  BEGIN /* local is unique */

                      IF non-secure THEN
                      BEGIN
                       send  END-NODE CHALLENGE NAME
                            REGISTRATION RESPONSE;
                       return;
                      END

                      REPEAT
                       send NAME QUERY REQUEST;
                       pause(UCAST_REQ_RETRY_TIMEOUT);
                      UNTIL response received or
                           retransmit count exceeded
                      IF no response received or
                           NEGATIVE NAME QUERY RESPONSE
                            received THEN
                      BEGIN
                       update data base - remove entry;
                       update data base - add new entry;
                       send POSITIVE NAME REGISTRATION RESPONSE;
                       return;
                      END
                      ELSE
                      BEGIN
                       /*
                        * name still being held
                        * by challenged node
                        */

                        send NEGATIVE NAME REGISTRATION RESPONSE;
                      END
                  END /* local is unique */
                  ELSE
                  BEGIN /* local is group  */

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                       /*
                        * existing entry is a group name
                        */

                       update data base - remove entry;
                       update data base - add new entry;
                       send POSITIVE NAME REGISTRATION RESPONSE;
                       return;
                  END /* local is group */
             END /* names exists */
             ELSE
             BEGIN /* does not exist */

                  /* name does not exist in data base */

                  update data base - add new entry;
                  send POSITIVE NAME REGISTRATION RESPONSE;
                  return;
             END /* does not exist */

        NAME RELEASE REQUEST:

             /*
              * secure server may choose to disallow
              * a node from deleting a name
              */

             update data base - remove entry;
             send POSITIVE NAME RELEASE RESPONSE;
             return;

        NAME UPDATE REQUEST:

             /*
              * End-node completed a successful challenge,
              * no update database
              */

             IF secure server THEN
                  send NEGATIVE NAME REGISTRATION RESPONSE;
             ELSE
             BEGIN /* new entry */
                  IF entry already exists THEN
                       update data base - remove entry;
                  update data base - add new entry;
                  send POSITIVE NAME REGISTRATION RESPONSE;
                  start_timer(TTL);
             END

        NAME REFRESH REQUEST:
             check for consistency;

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             IF node not allowed to have name THEN
             BEGIN

                  /*
                   * tell end node that it can't have name
                   */
                  send NEGATIVE NAME REGISTRATION RESPONSE;
             END
             ELSE
             BEGIN

                  /*
                   * send confirmation response to the
                   * end node.
                   */
                  send POSITIVE NAME REGISTRATION;
                  start_timer(TTL);
             END
             return;
        END /* case */
   END /* procedure */

5.1.4.2.  NBNS TIMER INITIATED PROCESSING

   A NS node uses timers to flush out entries from the data base.
   Each entry in the data base is removed when its timer expires.
   This time value is a multiple of the refresh TTL established when
   the name was registered.

   PROCEDURE timer_expired()

   /*
    * processing initiated by expiration of TTL for a given name
    */

   BEGIN
        /*
         * NBNS can (optionally) ensure
         * that the node is actually down
         * by sending a NODE STATUS REQUEST.
         * If such a request is sent, and
         * no response is received, it can
         * be assumed that the node is down.
         */
        remove entry from data base;
   END


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