Subject: Correct version 0.12 DLSW (6 of 8)

From: "Alan K. Bartky, Manager of Technology" <[email-masked]>
Date: Fri, 19 Aug 94 18:06:31 PDT

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Here is the correct part 6 of 8

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RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

   that are known to be able to reach the given NetBIOS name.  If the NetBIOS name
   is not in the table, the NETBIOS_NQ message will be sent to all known Data Link
   Switches.

   For SNA, the DISCONNECTED state is exited upon receipt of a CANUREACH message by
   a prospective target Data Link Switch, or upon receipt of an ICANREACH message
   by the origin Data Link Switch.  In the former case, the Data Link Switch will
   issue a Test command to the target station (i.e., DLC_START_DL signal is
   presented to DLC).  In the later case, a Test response is sent to the origin
   station (i.e., DLC_RESOLVE_R will be issued) and a REACH_ACK message will be
   returned to the target Data Link Switch.

     Note 1-  Some implementations will not send a Test response, but will send a
     Test command to the station that originated the resolve procedure (i.e., a
     DLC_START_DL will be issued) in order to start the data link.

   For NetBIOS, the DISCONNECTED state is exited upon the receipt of a NETBIOS_NQ
   message by the prospective target Data Link Switch, or upon the receipt of a
   NETBIOS_NR message by the origin Data Link Switch.  In the former case, the Data
   Link Switch will send a NB_Name_Query frame.  In the later case, the Data Link
   Switch will send a NB_Name_Recognized frame to the origin station and a
   REACH_ACK message will be returned to the target Data Link Switch.

     Note 2-  Some implementations will also send a Test command (i.e., a
     DLC_START_DL will be issued) to the station that originated the name
     resolution in order to start the data link.

7.2.2. RESOLVE_PENDING State

      +----------------------+-----------------------+-----------------------+
      |        Event         |      Action(s)        |      Next State       |
      +----------------------+-----------------------+-----------------------+
      | Receive DATAFRAME    | DLC_DGRM              |                       |
      +----------------------+-----------------------+-----------------------+
      | DLC_DL_STARTED       | If LF value of        | If LF value of        |
      |                      | DLC_DL_STARTED        | DLC_DL_STARTED        |
      |                      | is greater than or    | is greater than or    |
      |                      | equal to LF Size of   | equal to LF Size of   |
      |                      | CANUREACH_cs or LF    | CANUREACH_cs or LF    |
      |                      | Size Control bit set: | Size Control bit set: |
      |                      |   Send ICANREACH      |   CIRCUIT_PENDING     |
      |                      | else:                 | else:                 |
      |                      |   Send DLC_HALT_DL    |   HALT_PENDING_NOACK  |
      +----------------------+-----------------------+-----------------------+
      | DLC_ERROR            |                       | DISCONNECTED          |
      +----------------------+-----------------------+-----------------------+
      | DLC_DGRM             | Send DATAFRAME        |                       |
      +----------------------+-----------------------+-----------------------+

   The RESOLVE_PENDING state is entered upon receipt of a CANUREACH message or a
   NETBIOS_NQ message by the target DLSw.  In the former case, a data link is
   started, causing a Test command to be sent by the DLC.  In the later case, a
   NB_Name_Query frame is sent.  This frame is directed to a group MAC address.

   Any CANUREACH messages received in the RESOLVE_PENDING state will be responded
   to if a DLC_DL_STARTED signal is received.  The Data Link Switch may also update

AIW DLSw Related Interest Group                                  [Page 48]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

   its topology information based upon the origin MAC address information in each
   CANUREACH message.

   Upon the receipt of a DLC_DL_STARTED signal in the RESOLVE_PENDING state, the
   Data Link Switch may update its topology table base upon the remote MAC address
   information.  The ICANREACH message should be returned to all Data Link Switches
   that had sent a CANUREACH message.  In a similar fashion, the Data Link Switch
   may update its topology table upon the receipt of a NB_Name_Recognized frame and
   a NETBIOS_NR message will be returned to all Data Link Switches that have sent a
   NETBIOS_NQ message.

   The RESOLVE_PENDING state is exited once the data link has been started (i.e., a
   DLC_DL_STARTED signal is received as a result of a Test response received by the
   DLC) or a NB_Name_Recognized frame is received (i.e., a DLC_DGRM signal is
   received).  The target Data Link Switch will then enter the CIRCUIT_PENDING
   state.

     Note:  Some implementations will also send a Test command in order to start
     the data link to the station that responded to the Name Query frame (i.e., a
     DLC_START_DL will be issued).

7.2.3. CIRCUIT_START State

      +----------------------+---------------------+-------------------------+
      |        Event         |      Action(s)      |      Next State         |
      +----------------------+---------------------+-------------------------+
      | Receive CANUREACH_cs | If origin MAC addr  | If DLC_START_DL         |
      | for circuit in       | in CANUREACH_cs is  | issued:                 |
      | opposite direction   | greater than origin |   RESOLVE_PENDING       |
      |                      | MAC addr of circuit:|                         |
      |                      |   DLC_START_DL      |                         |
      |                      | else:               |                         |
      |                      |   no action taken   |                         |
      +----------------------+---------------------+-------------------------+
      | Receive ICANREACH_cs | If LF Size Control  | If LF Size Control      |
      |                      | bit set and LF Size | bit set and LF Size     |
      |                      | is not negotiable:  | is not negotiable:      |
      |                      |   Send HALT_DL_NOACK|   DISCONNECTED          |
      |                      | else:               | else:                   |
      |                      |   Send REACH_ACK,   |   If Connected:         |
      |                      |   If Connected:     |     CONNECT_PENDING     |
      |                      |     Send CONTACT    |   else:                 |
      |                      |   else:             |     CIRCUIT_ESTABLISHED |
      |                      |     no action taken |                         |
      |                      |                     |                         |
      +----------------------+---------------------+-------------------------+
      | DLC_DGRM             | Send DATAFRAME      |                         |
      +----------------------+---------------------+-------------------------+
      | CS_TIMER_EXP         |                     | DISCONNECTED            |
      +----------------------+---------------------+-------------------------+

AIW DLSw Related Interest Group                                  [Page 49]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

7.2.4. CIRCUIT_PENDING State

      +----------------------+---------------------+----------------------+
      |        Event         |      Action(s)      |      Next State      |
      +----------------------+---------------------+----------------------+
      | Receive CONTACT      | DLC_CONTACT         | CONTACT_PENDING      |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL      | DLC_HALT_DL         | HALT_PENDING         |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL_NOACK| DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+
      | Receive REACH_ACK    | If Connected:       | If Connected:        |
      |                      |  Send CONTACT       |  CONNECT_PENDING,    |
      |                      |                     | else:                |
      |                      |                     |  CIRCUIT_ESTABLISHED |
      +----------------------+---------------------+----------------------+
      | Receive XIDFRAME     | DLC_XID             |                      |
      +----------------------+---------------------+----------------------+
      | Receive DGRMFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | Receive DATAFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | DLC_CONTACTED        | If UA is sent in    |                      |
      |                      | response to SABME:  |                      |
      |                      |   DLC_ENTER_BUSY    |                      |
      |                      | else:               |                      |
      |                      |   no action taken   |                      |
      +----------------------+---------------------+----------------------+
      | DLC_ERROR            | Send HALT_DL        | DISCONNECT_PENDING   |
      +----------------------+---------------------+----------------------+
      | DLC_XID              | Send XIDFRAME       |                      |
      +----------------------+---------------------+----------------------+
      | DLC_DGRM             | Send DGRMFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | XPORT_FAILURE        | DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+

   The CIRCUIT_PENDING state is entered by the target Data Link Switch following
   the sending of an ICANREACH message or the sending of a NETBIOS_NR message.  In
   this state it is awaiting the reception of a REACH_ACK message from the origin
   Data Link Switch.  If a connection does not exist with the target station (i.e.,
   the normal case), the Data Link Switch will enter the CIRCUIT_ESTABLISHED state.

   If the target Data Link Switch happens to receive a SABME command from the
   target station while in the CIRCUIT_PENDING state (i.e., a DLC_CONTACTED signal
   received from the DLC), the reception of the REACH_ACK message will cause the
   Data Link Switch to enter the CONNECT_PENDING state and to send a CONTACT
   message to the other Data Link Switch.  Thus the target Data Link Switch has
   assumed the role of the origin Data Link Switch.

AIW DLSw Related Interest Group                                  [Page 50]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

7.2.5. CONNECT_PENDING State

      +----------------------+---------------------+----------------------+
      |        Event         |      Action(s)      |      Next State      |
      +----------------------+---------------------+----------------------+
      | Receive CONTACTED    | If UA was sent in   | CONNECTED            |
      |                      | response to SABME:  |                      |
      |                      |   DLC_EXIT_BUSY     |                      |
      |                      | else:               |                      |
      |                      |   DLC_CONTACT       |                      |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL      | DLC_HALT_DL         | HALT_PENDING         |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL_NOACK| DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+
      | Receive DGRMFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | Receive DATAFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | Receive ICANREACH    | Send HALT_DL_NOACK  |                      |
      +----------------------+---------------------+----------------------+
      | Receive NETBIOS_NR   | Send HALT_DL_NOACK  |                      |
      +----------------------+---------------------+----------------------+
      | DLC_RESET            | Send RESTART_DL     | CIRCUIT_RESTART      |
      +----------------------+---------------------+----------------------+
      | DLC_ERROR            | Send HALT_DL        | DISCONNECT_PENDING   |
      +----------------------+---------------------+----------------------+
      | DLC_DGRM             | Send DGRMFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | XPORT_FAILURE        | DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+

   The CONNECT_PENDING state is entered by the origin Data Link Switch when a
   DLC_CONTACTED signal has been received from the DLC (i.e., a SABME command has
   been received).  A CONTACT message is then issued.  The state is exited upon the
   receipt of a CONTACTED message from the target Data Link Switch.  If a DLC_RESET
   signal is received, the local data link is restarted and a RESTART_DL message is
   sent to the remote DLSw.

     Note:  Some implementations will also send a Test command in order to restart
     the data link to the station that sent the SABME command (i.e., a DLC_START_DL
     will be issued).

AIW DLSw Related Interest Group                                  [Page 51]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

7.2.6. CIRCUIT_ESTABLISHED State

      +----------------------+---------------------+----------------------+
      |        Event         |      Action(s)      |      Next State      |
      +----------------------+---------------------+----------------------+
      | Receive CONTACT      | DLC_CONTACT         | CONTACT_PENDING      |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL      | DLC_HALT_DL         | HALT_PENDING         |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL_NOACK| DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+
      | Receive XIDFRAME     | DLC_XID             |                      |
      +----------------------+---------------------+----------------------+
      | Receive DGRMFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | Receive DATAFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | Receive ICANREACH    | Send HALT_DL_NOACK  |                      |
      +----------------------+---------------------+----------------------+
      | Receive NETBIOS_NR   | Send HALT_DL_NOACK  |                      |
      +----------------------+---------------------+----------------------+
      | DLC_CONTACTED        | Send CONTACT        | CONNECT_PENDING      |
      |                      | If UA is sent in    |                      |
      |                      | response to SABME:  |                      |
      |                      |   DLC_ENTER_BUSY    |                      |
      |                      | else:               |                      |
      |                      |   no action taken   |                      |
      +----------------------+---------------------+----------------------+
      | DLC_ERROR            | Send HALT_DL        | DISCONNECT_PENDING   |
      +----------------------+---------------------+----------------------+
      | DLC_DGRM             | Send DGRMFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | DLC_XID              | Send XIDFRAME       |                      |
      +----------------------+---------------------+----------------------+
      | XPORT_FAILURE        | DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+

   The CIRCUIT_ESTABLISHED state is entered by the origin Data Link Switch from the
   DISCONNECTED state, and by the target Data Link Switch from the CIRCUIT_PENDING
   state.  The state is exited when a connection is started (i.e., DLC receives a
   SABME command).  The next state is CONTACT_PENDING for the target Data Link
   Switch and CONNECT_PENDING for the origin Data Link Switch.

AIW DLSw Related Interest Group                                  [Page 52]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

7.2.7. CONTACT_PENDING State

      +----------------------+---------------------+----------------------+
      |        Event         |      Action(s)      |      Next State      |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL      | DLC_HALT_DL         | HALT_PENDING         |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL_NOACK| DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+
      | Receive RESTART_DL   | DLC_HALT_DL         | RESTART_PENDING      |
      +----------------------+---------------------+----------------------+
      | Receive DGRMFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | Receive DATAFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | DLC_CONTACTED        | Send CONTACTED      | CONNECTED            |
      +----------------------+---------------------+----------------------+
      | DLC_ERROR            | Send HALT_DL        | DISCONNECT_PENDING   |
      +----------------------+---------------------+----------------------+
      | DLC_DGRM             | Send DGRMFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | XPORT_FAILURE        | DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+

   The CONTACT_PENDING state is entered by the target Data Link Switch upon the
   receipt of a CONTACT message.  This causes the Data Link Switch to issue a
   DLC_CONTACT signal to the DLC (i.e., DLC sends a SABME command).  This state is
   then exited upon the receipt of a DLC_CONTACTED signal from the DLC (i.e., a UA
   response received).

   If a RESTART_DL message is received, indicating that the remote Data Link Switch
   has received a DLC_RESET signal, the local Data Link Switch will send a DISC
   command frame on the adjacent LAN (i.e., DLC_HALT_DL signal) and enter the
   RESTART_PENDING state.

AIW DLSw Related Interest Group                                  [Page 53]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

7.2.8. CONNECTED State

      +----------------------+---------------------+----------------------+
      |        Event         |      Action(s)      |      Next State      |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL      | DLC_HALT_DL         | HALT_PENDING         |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL_NOACK| DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+
      | Receive RESTART_DL   | DLC_HALT_DL         | RESTART_PENDING      |
      +----------------------+---------------------+----------------------+
      | Receive DGRMFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | Receive INFOFRAME    | DLC_INFO            |                      |
      +----------------------+---------------------+----------------------+
      | Receive DATAFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | Receive XIDFRAME     | If non-activation   |                      |
      |                      | XID3:               |                      |
      |                      |   DLC_XID           |                      |
      +----------------------+---------------------+----------------------+
      | Receive ICANREACH    | Send HALT_DL_NOACK  |                      |
      +----------------------+---------------------+----------------------+
      | Receive NETBIOS_NR   | Send HALT_DL_NOACK  |                      |
      +----------------------+---------------------+----------------------+
      | Receive ENTER_BUSY   | DLC_ENTER_BUSY      |                      |
      +----------------------+---------------------+----------------------+
      | Receive EXIT_BUSY    | DLC_EXIT_BUSY       |                      |
      +----------------------+---------------------+----------------------+
      | Rec TEST_CIRCUIT_REQ | Snd TEST_CIRCUIT_RSP|                      |
      +----------------------+---------------------+----------------------+
      | DLC_RESET            | Send RESTART_DL     | CIRCUIT_RESTART      |
      +----------------------+---------------------+----------------------+
      | DLC_ERROR            | Send HALT_DL        | DISCONNECT_PENDING   |
      +----------------------+---------------------+----------------------+
      | DLC_DGRM             | Send DGRMFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | DLC_INFO             | Send INFOFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | DLC_XID              | If non-activation   |                      |
      |                      | XID3:               |                      |
      |                      |   Send XIDFRAME     |                      |
      +----------------------+---------------------+----------------------+
      | XPORT_FAILURE        | DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+

   The CONNECTED state is entered by the origin Data Link Switch from the
   CONNECT_PENDING state upon the receipt of a CONTACTED message.  The CONNECTED
   state is entered by the target Data Link Switch from the CONTACT_PENDING state
   upon the receipt of a DLC_CONTACTED signal.  At this time, the target Data Link
   Switch will return a CONTACTED message to the origin Data Link Switch.

   The CONNECTED state is exited usually under one of two conditions: a DLC_ERROR
   signal received from the DLC (e.g., a DISC command received by the local DLC),
   or a HALT_DL message received from the other Data Link Switch (e.g., a DISC
   command received by the remote DLC).

AIW DLSw Related Interest Group                                  [Page 54]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

   A SABME command (i.e., a DLC_RESET signal) received by either Data Link Switch
   will also cause the two Data Link Switches to leave the CONNECTED state and
   eventually restart a new circuit.

     Note:  Some implementations will also send a Test command in order to  restart
     the data link to the station that sent the SABME command  (i.e., a
     DLC_START_DL will be issued).

   Following the receipt of a reset signal, the Data Link Switch will send a
   RESTART_DL message to the other Data Link Switch and will enter the
   CIRCUIT_RESTART state.  Upon the receipt of the RESTART_DL message, the remote
   Data Link Switch will send a DISC command (i.e., DLC_HALT_DL signal) and enter
   the RESTART_PENDING state.

7.2.9. CIRCUIT_RESTART State

      +----------------------+---------------------+----------------------+
      |        Event         |      Action(s)      |      Next State      |
      +----------------------+---------------------+----------------------+
      | Receive DL_RESTARTED | If Connected:       | If Connected:        |
      |                      |  Send CONTACT       |  CONNECT_PENDING,    |
      |                      |                     | else:                |
      |                      |                     |  CIRCUIT_ESTABLISHED |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL_NOACK| DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+
      | Receive DATAFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | DLC_ERROR            | Send HALT_DL        | DISCONNECT_PENDING   |
      +----------------------+---------------------+----------------------+
      | DLC_DGRM             | Send DATAFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | XPORT_FAILURE        | DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+

   The CIRCUIT_RESTART state is entered if a DLC_RESET signal is received from the
   local DLC.  This was caused by the receipt of a SABME command while a connection
   was currently active.  A DM response will be issued to the SABME command and the
   Data Link Switch will attempt to restart the end-to- end circuit.

   The CIRCUIT_RESTART state is exited through one of two transitions.  The next
   state depends upon the time the local DLC has reached the contacted state (i.e.,
   a DLC_CONTACTED signal is presented) relative to the receipt of the DL_RESTARTED
   message.  This signal is caused by the origin station resending the SABME
   command that initially caused the DATA Link Switch to enter the CIRCUIT_RESTART
   state.  The two cases are as follows:

          1) DL_RESTARTED message received before the DLC_CONTACTED signal-  In
          this case, the CIRCUIT_ESTABLISHED state is entered.

          2) DL_RESTARTED message received after the DLC_CONTACTED signal-  In this
          case, the CONNECT_PENDING state is entered.

AIW DLSw Related Interest Group                                  [Page 55]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

7.2.10. DISCONNECT_PENDING State

      +----------------------+---------------------+----------------------+
      |        Event         |      Action(s)      |      Next State      |
      +----------------------+---------------------+----------------------+
      | Receive DL_HALTED    |                     | DISCONNECTED         |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL      | Send DL_HALTED      |                      |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL_NOACK|                     | DISCONNECTED         |
      +----------------------+---------------------+----------------------+
      | Receive DATAFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | DLC_DGRM             | Send DATAFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | XPORT_FAILURE        |                     | DISCONNECTED         |
      +----------------------+---------------------+----------------------+

   The DISCONNECT_PENDING state is entered when a DLC_ERROR signal is received from
   the local DLC.  Upon receipt of this signal, a HALT message is sent.  Once an
   DL_HALTED message is received, the state is exited, and the Data Link Switch
   enters the DISCONNECTED state.

7.2.11. RESTART_PENDING State

      +----------------------+---------------------+----------------------+
      |        Event         |      Action(s)      |      Next State      |
      +----------------------+---------------------+----------------------+
      | Receive HALT_DL_NOACK|                     | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+
      | Receive DATAFRAME    | DLC_DGRM            |                      |
      +----------------------+---------------------+----------------------+
      | DLC_DL_HALTED        | Send DL_RESTARTED   | CIRCUIT_ESTABLISHED  |
      +----------------------+---------------------+----------------------+
      | DLC_ERROR            | Send HALT_DL        | DISCONNECT_PENDING   |
      +----------------------+---------------------+----------------------+
      | DLC_DGRM             | Send DATAFRAME      |                      |
      +----------------------+---------------------+----------------------+
      | XPORT_FAILURE        | DLC_HALT_DL         | HALT_PENDING_NOACK   |
      +----------------------+---------------------+----------------------+

   The RESTART_PENDING state is entered upon the receipt of a RESTART_DL message
   from the remote DLSw while the local Data Link Switch is in either the
   CONTACT_PENDING state or the CONNECTED state.  These cause the local DLC to
   issue a DISC command.  Upon the receipt of the UA response (DLC_DL_HALTED), the
   data link is restarted, a DL_RESTARTED message is returned to the remote DLSw,
   and the CIRCUIT_ESTABLISHED state is entered.

     Note:  Some implementations will send a Test command in order to restart the
     data link to the target station (i.e., a DLC_START_DL will be issued) prior to
     sending the DL_RESTARTED message.

AIW DLSw Related Interest Group                                  [Page 56]