Subject: Correct version 0.12 DLSW (8 of 8)

From: "Alan K. Bartky, Manager of Technology" <[email-masked]>
Date: Fri, 19 Aug 94 18:08:59 PDT

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Here is the correct part 8 of 8

Combine parts 1 through 8 to get a complete ASCII document.

Regards and happy reading,

Alan

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

   UA              DLC_CONTACTED   CONTACT         DLC_CONTACT
   ----------->    ----------->    ----------->    ----------->
                      connected                       connected

      IFRAMEs        DLC_INFOs        IFRAMEs        DLC_INFOs
   <----------->   <------------>  <------------>  <------------>
   --------------------------------------------------------------------------

AIW DLSw Related Interest Group                                  [Page 67]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

   Here is an example of a switched SDLC PU 2.0 device as the origin station.

      ======                            ___                           ======
      |    |        ---------        __/   \__       ---------        |    |
      |    |      __|  _|_  |__     /   IP    \    __|  _|_  |__      |    |
      ======        |   |   |      <  Network  >     |   |   |        ======
     /______\       ---------       \__     __/      ---------       /______\
      Origin       Origin DLSw         \___/        Target DLSw      Target
      Station        partner                          partner        Station

                   disconnected                     disconnected

   implementer's   DLC_RESOLVE_C   CANUREACH_ex
   choice (power   ----------->    ----------->
   up, configuration
   change, receipt                   ICANREACH_ex
   of XID, never, etc.)              <-----------

   XID(null)       DLC_XID(null)   CANUREACH_cs    DLC_START_DL
   ----------->    ----------->    ----------->    ----------->
                   circuit_start                   resolve_pending

                                     ICANREACH_cs    DLC_DL_STARTED
                                     <-----------    <-----------
               circuit_established                 circuit_pending
                                   REACH_ACK
                                   ----------->   circuit_established

                                   XIDFRAME        DLC_XID
                                   ----------->    ----------->

              XID         DLC_XID        XIDFRAME         DLC_XID
     <-----------    <-----------    <-----------    <-----------

   XID             DLC_XID         XIDFRAME        DLC_XID
   ----------->    ----------->    ----------->    ----------->

             SNRM     DLC_CONTACT       CONTACTED    DLC_CONTACTED
     <-----------    <-----------    <-----------    <-----------
                   contact_pending                 connect_pending

   UA              DLC_CONTACTED   CONTACT         DLC_CONTACT
   ----------->    ----------->    ----------->    ----------->
                      connected                       connected

      IFRAMEs        DLC_INFOs        IFRAMEs        DLC_INFOs
   <------------>  <------------>  <------------>  <------------>

AIW DLSw Related Interest Group                                  [Page 68]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

   Here is an example of a leased SDLC PU 2.0 device as the target station.

      ======                            ___                           ======
      |    |        ---------        __/   \__       ---------        |    |
      |    |      __|  _|_  |__     /   IP    \    __|  _|_  |__      |    |
      ======        |   |   |      <  Network  >     |   |   |        ======
     /______\       ---------       \__     __/      ---------       /______\
      Origin       Origin DLSw         \___/        Target DLSw       Target
      Station        partner                          partner         Station
                                                                      (SDLC)
                   disconnected                    disconnected

                   DLC_RESOLVE_C   CANUREACH_ex
                   ----------->    ----------->    reply if virtual MAC/SAP for
                                                   SDLC station is configured,
                                                   if SDLC station responds to
                                     ICANREACH_ex  TEST/SNRM/DISC, etc.
                                     <-----------

                   DLC_XID         CANUREACH_cs    DLC_START_DL    SNRM
                   ----------->    ----------->    ----------->    ----------->
                   circuit_start                   resolve_pending

                                     ICANREACH_cs    DLC_DL_STARTED            UA
                                     <-----------    <-----------    <-----------
               circuit_established                 circuit_pending
                                                                   RNR
                                   REACH_ACK                       ----------->
                                   ----------->   circuit_established

                                   XIDFRAME        DLC_XID
                                   ----------->    ----------->    respond with
                                                                   XID configured
                                                                   for station or
                                                                   forward XID to
                                                                   station and
                          DLC_XID        XIDFRAME         DLC_XID  send response
                     <-----------    <-----------    <-----------

                   DLC_CONTACTED   CONTACT         DLC_CONTACT     RR
                   ----------->    ----------->    ----------->    ----------->
                   connect_pending                contact_pending

                      DLC_CONTACT       CONTACTED    DLC_CONTACTED
                     <-----------    <-----------    <-----------
                     connected                        connected

                     DLC_INFOs        IFRAMEs        DLC_INFOs        IFRAMEs
                   <------------>  <------------>  <------------>  <------------>

AIW DLSw Related Interest Group                                  [Page 69]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

   Here is an example of a switched SDLC PU 2.0 device as the target station.

      ======                            ___                           ======
      |    |        ---------        __/   \__       ---------        |    |
      |    |      __|  _|_  |__     /   IP    \    __|  _|_  |__      |    |
      ======        |   |   |      <  Network  >     |   |   |        ======
     /______\       ---------       \__     __/      ---------       /______\
      Origin       Origin DLSw         \___/        Target DLSw       Target
      Station        partner                          partner         Station
                                                                      (SDLC)
                   disconnected                    disconnected

                   DLC_RESOLVE_C   CANUREACH_ex
                   ----------->    ----------->    reply if virtual MAC/SAP
                                                   for SDLC station is
                                                   configured, if SDLC
                                                   station responds to
                                     ICANREACH_ex  TEST/XID/SNRM/DISC, etc.
                                     <-----------

                   DLC_XID         CANUREACH_cs    DLC_START_DL    XID
                   ----------->    ----------->    ----------->    ----------->
                   circuit_start                   resolve_pending

                                     ICANREACH_cs    DLC_DL_STARTED           XID
                                     <-----------    <-----------    <-----------
               circuit_established                 circuit_pending
                                   REACH_ACK
                                   ----------->   circuit_established

                                   XIDFRAME        DLC_XID
                                   ----------->    ----------->    respond with
                                                                   XID received
                          DLC_XID        XIDFRAME         DLC_XID  above
                     <-----------    <-----------    <-----------

                   DLC_CONTACTED   CONTACT         DLC_CONTACT     SNRM
                   ----------->    ----------->    ----------->    ----------->
                   connect_pending                contact_pending

                      DLC_CONTACT       CONTACTED    DLC_CONTACTED             UA
                     <-----------    <-----------    <-----------    <-----------
                     connected                        connected

                     DLC_INFOs        IFRAMEs        DLC_INFOs        IFRAMEs
                   <------------>  <------------>  <------------>  <------------>

AIW DLSw Related Interest Group                                  [Page 70]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

   Here is an example of an SDLC T2.1 device as the target station.  (SDLC T2.1
   origin station would look just like the LAN T2.1 origin station)
      ======                            ___                           ======
      |    |        ---------        __/   \__       ---------        |    |
      |    |      __|  _|_  |__     /   IP    \    __|  _|_  |__      |    |
      ======        |   |   |      <  Network  >     |   |   |        ======
     /______\       ---------       \__     __/      ---------       /______\
      Origin       Origin DLSw         \___/        Target DLSw      Target
      Station        partner                          partner        Station

                   disconnected                    disconnected

                   DLC_RESOLVE_C   CANUREACH_ex
                   ----------->    ----------->    implementer's choice
                                                   (virtual MAC/SAP configured,
                                                    check to see if station
                                                    is powered up using
                                     ICANREACH_ex   TEST/XID/DISC, etc.)
                                     <-----------

                   DLC_XID         CANUREACH_cs    DLC_START_DL    null XID
                   ----------->    ----------->    ----------->    ---------->
                   circuit_start                   resolve_pending

                                     ICANREACH_cs    DLC_DL_STARTED           XID
                                     <-----------    <-----------    <-----------
               circuit_established                 circuit_pending
                                   REACH_ACK
                                   ----------->   circuit_established

                                   XIDFRAME        DLC_XID
                                   ----------->    ----------->    respond with
                                                                   XID received
                          DLC_XID        XIDFRAME         DLC_XID  above
                     <-----------    <-----------    <-----------

                      DLC_XIDs       XIDFRAMEs        DLC_XIDs          XIDs
                   <------------>  <------------>  <------------>  <------------>

                   DLC_CONTACTED   CONTACT         DLC_CONTACT     SABME
                   ----------->    ----------->    ----------->    ----------->
                   connect_pending                 contact_pending

                      DLC_CONTACT       CONTACTED    DLC_CONTACTED             UA
                     <-----------    <-----------    <-----------    <-----------
                     connected                        connected

                     DLC_INFOs        IFRAMEs        DLC_INFOs        IFRAMEs
                   <------------>  <------------>  <------------>  <------------>

8.2. Link Restart Protocols

   The following figure depicts the protocol flows that result from restarting the
   end-to-end connection.  This causes the Data Link Switches to terminate the
   existing connection and to enter the Circuit Established state awaiting the
   start of a new connection.

AIW DLSw Related Interest Group                                  [Page 71]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

     Data Link   Data Link                     Data Link   Data Link
      Control     Switch                        Switch      Control
     ---------------------                     ---------------------
          +-----------+                             +-----------+
          | Connected |                             | Connected |
    SABME +-----------+                             +-----------+
   ----------->                 RESTART_DL
      DM           ------------------------------------->     DISC
   <-----------                                               -------->
                                                               UA
                         DL_RESTARTED (Case 1)              <--------
                   <-------------------------------------
          +-----------+                             +-----------+
          |Circuit Est|                             |Circuit Est|
          +-----------+                             +-----------+
                        ........... or ...........
    SABME
   ----------->           DL_RESTARTED (Case 2)
       UA          <-------------------------------------
   <-----------                                     +-----------+
                                                    |Circuit Est|
                                CONTACT             +-----------+
      RNR           ------------------------------------>
   <----------

             Figure 5.  DLSw Link Restart Message Protocols

   Upon receipt of a SABME command from the origin station, the origin DLSw will
   send a RESTART_DL message to the target DLSw.  A DM response is also returned to
   the origin station and the data link is restarted.

   Upon receipt of the RESTART_DL message, the target DLSw will issue a DISC
   command to the target station.  The target station is expected to return a UA
   response.  The target DLSw will then restart its data link and send an
   DL_RESTARTED message back to the origin DLSw.  During this exchange of messages,
   both Data Link Switches change states from Connected state to Circuit
   Established state.

   If the origin station now resends the SABME command, the origin DLSw will send a
   CONTACT message to the target DLSw.  If the SABME command is received prior to
   the receipt of the DL_RESTARTED message (case 2 in the figure), the CONNECT
   message is delayed until the DL_RESTARTED message is received.  The resulting
   protocol flows at this point parallel those given above for the connect
   sequence.

8.3. Disconnect Protocols

   The following figure depicts the protocol flows that result from the end system
   terminating an existing connection.  Not only is the connection terminated, but
   the circuit between the Data Link Switches is taken down.

AIW DLSw Related Interest Group                                  [Page 72]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

     Data Link  Data Link                      Data Link  Data Link
      Control    Switch                         Switch     Control
     --------------------                      --------------------
          +-----------+                             +-----------+
          | Connected |                             | Connected |
          +-----------+                             +-----------+
      DISC
   ---------->                  HALT_DL
       UA         ------------------------------------->      DISC
   <----------                                              --------->
                                                               UA
                               DL_HALTED                    <--------
                  <-------------------------------------
          +-----------+                             +-----------+
          |Disconnectd|                             |Disconnectd|
          +-----------+                             +-----------+

                          ......... or ..........

          +-----------+                             +-----------+
          | Connected |                             | Connected |
          +-----------+                             +-----------+
       DISC              TCP Connection Failure               DISC
   <--------     <------------------------------------>    --------->
        UA                                                     UA
    -------->                                               <--------
          +-----------+                             +-----------+
          |Disconnectd|                             |Disconnectd|
          +-----------+                             +-----------+

              Figure 6.  DLSw Disconnect Message Protocols

   Upon receipt of a DISC command from the origin station, the origin DLSw will
   reply with a UA response and issue a HALT_DL message to the target DLSw.  Upon
   receipt of the HALT_DL message, the target DLSw will send a DISC command to the
   target station.  The target station will then respond with a UA response,
   causing the target DLSw to return a DL_HALTED message to the origin DLSw.
   During this exchange of messages, both Data Link Switches change states from the
   Connected state to the Disconnected state.

   If the TCP connection between two Data Link Switches fails, all connections that
   are currently multiplexed on the failed TCP connection will be taken down.  This
   implies that both Data Link Switches will send DISC commands to all the local
   systems that are associated with the failed connections.  Upon sending the DISC
   command, the Data Link Switch will enter the DISCONNECT state for each circuit.

Acknowledgments

   Original RFC 1434 Authors:

      Roy C. Dixon, IBM
      David M. Kushi, IBM

   Chair of  APPN Impementers Workshop Data Link Switching Related Interest Group:

      Louise Herndon Wells, ITI

AIW DLSw Related Interest Group                                  [Page 73]
RFC XXXX      DLSw: Switch-to-Switch Protocol              August 1994

   Working Group Chairs (and significant contributors to this document):

      Connect/Disconnect (State Machines): Steve Klein, IBM
      Capabilities Exchange: Wayne Clark, Cisco Systems
      Flow Control (Adaptive Pacing): Shannon Nix, Metaplex

   Other significant contributors:

      Gene Cox, IBM
      Peter Gayek, IBM
      Paul Brittain, Data Connection Limited

References

     1) ISO 8802-2/IEEE Std 802.2 International Standard,
        Information Processing Systems, Local Area Networks, Part 2:
        Logical Link Control, December 31, 1989

     2) The NETBIOS Frames Protocol, IBM Local Area Technical
        Reference, SC30-3383-03, Chapter 5, December 1990

     3) ISO/IEC DIS 10038 DAM 2, MAC Bridging, Source Routing
        Supplement, December 1991

   Security Considerations

   Security issues are not discussed in this memo.

Editor's Address

   Alan K. Bartky
   Manager of Technology
   Sync Research Inc.
   7 Studebaker
   Irvine, CA 91728-2013

   Phone: (714)588-2070
   EMail: [email-masked]

   Note: Any questions or comments relative to the contents of this RFC should be
   sent to the following Internet address:
      [email-masked].  This address will be used to coordinate
   the handling of responses.

   NOTE 1:  This is a widely subscribed mailing list and messages sent to this
   address will be sent to all members of the DLSw mailing list.  For specific
   questions relating to subscribing to the AIW and any of it's working groups send
   email to:
      [email-masked]

   NOTE 2:  These mailing lists and addresses are subject to change.

AIW DLSw Related Interest Group                                  [Page 74]