[Search] [txt|pdf|bibtex] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 rfc2371                               
Transaction Internet Protocol Working Group                      J. Lyon
Internet-Draft                                                 Microsoft
Obsoletes <draft-lyon-itp-nodes-02.txt>                         K. Evans
Expires in 6 months                                             J. Klein
                                                        Tandem Computers
                                                      October 20th, 1997

                     Transaction Internet Protocol
                               Version 2.0

                     <draft-lyon-itp-nodes-03.txt>

Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six=20
   months and may be updated, replaced, or obsoleted by other documents=20
   at any time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   To learn the current status of any Internet-Draft, please check the
   "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
   Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
   munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
   ftp.isi.edu (US West Coast).

Abstract

   In many applications where different nodes cooperate on some work,
   there is a need to guarantee that the work happens atomically. That
   is, each node must reach the same conclusion as to whether the work
   is to be completed, even in the face of failures.  This document
   proposes a simple, easily-implemented protocol for achieving this
   end.



















Lyon, et al                                                     [Page 1]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

Table of Contents

            Status of this memo                                        1
            Abstract                                                   1
            Table of Contents                                          2
   1.       Introduction                                               3
   2.       Example Usage                                              3
   3.       Transactions                                               4
   4.       Connections                                                4
   5.       Transaction Identifiers                                    5
   6.       Pushing vs. Pulling Transactions                           5
   7.       Endpoint Identification                                    6
   8.       TIP Uniform Resource Locators                              7
   9.       States of a Connection                                     8
   10.      Protocol Versioning                                        9
   11.      Commands and Responses                                    10
   12.      Command Pipelining                                        10
   13.      TIP Commands                                              11
   14.      Error Handling                                            16
   15.      Connection Failure and Recovery                           16
   16.      Security Considerations                                   18
   17.      Significant changes from previous version                 19
            References                                                19
            Authors' Addresses                                        19
            Comments                                                  19
   App A.   The TIP Multiplexing Protocol Version 2.0                 21





























Lyon, et al                                                     [Page 2]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

1. Introduction

   The standard method for achieving atomic commitment is the two-phase
   commit protocol; see [1] for an introduction to atomic commitment and
   two-phase commit protocols.

   Numerous two-phase commit protocols have been implemented over the
   years.  However, none of them has become widely used in the Internet,
   due mainly to their complexity.  Most of that complexity comes from
   the fact that the two-phase commit protocol is bundled together with
   a specific program-to-program communication protocol, and that
   protocol lives on top of a very large infrastructure.

   This memo proposes a very simple two-phase commit protocol.  It
   achieves its simplicity by specifying only how different nodes agree
   on the outcome of a transaction; it allows (even requires) that the
   subject matter on which the nodes are agreeing be communicated via
   other protocols. By doing so, we avoid all of the issues related to
   application communication semantics and data representation
   (to name just a few). Independent of the application communication=20
   protocol a transaction manager may use the Transport Layer Security
   protocol [3] to authenticate other transaction managers and encrypt=20
   messages.=20
  =20
   It is envisioned that this protocol will be used mainly for a
   transaction manager on one Internet node to communicate with a
   transaction manager on another node. While it is possible to use
   this protocol for application programs and/or resource managers to
   speak to transaction managers, this communication is usually
   intra-node, and most transaction managers already have more-than-
   adequate interfaces for the task.

   While we do not expect this protocol to replace existing ones, we=20
   do expect that it will be relatively easy for many existing=20
   heterogeneous transaction managers to implement this protocol for
   communication with each other.

   Further supplemental information regarding the TIP protocol can be
   found in [5].

2. Example Usage

   Today the electronic shopping basket is a common metaphor at many
   electronic store-fronts. Customers browse through an electronic
   catalog, select goods and place them into an electronic shopping
   basket. HTTP servers [2] provide various means ranging from URL=20
   encoding to context cookies to keep track of client context (e.g.
   the shopping basket of a customer) and resume it on subsequent=20
   customer requests.=20

   Once a customer has finished shopping they may decide to commit=20
   their selection and place the associated orders. Most orders may have
   no relationship with each other except being executed as part of the
   same shopping transaction; others may be dependent on each other

Lyon, et al                                                     [Page 3]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997
 =20
   (for example, if made as part of a special offering). Irrespective of
   these details a customer will expect that all orders have been
   successfully placed upon receipt of a positive acknowledgment.=20

   Today's electronic store-fronts must implement their own special=20
   protocols to coordinate such placement of all orders. This=20
   programming is especially complex when orders are placed through=20
   multiple electronic store-fronts. This complexity limits the=20
   potential utility of internet applications, and constrains growth.

   The protocol described in this document intends to provide a standard
   for internet servers to achieve agreement on a unit of shared work=20
   (e.g. placement of orders in an electronic shopping basket).=20
   The server (e.g. a CGI program) placing the orders may want to start
   a transaction calling its local transaction manager, and ask
   other servers participating in the work to join the transaction.=20
   The server placing the orders passes a reference to the transaction=20
   as user data on HTTP requests to the other servers. The other=20
   servers call their transaction managers to start a local transaction
   and ask them to join the remote transaction using the protocol =20
   defined in this document. Once all orders have been placed, execution
   of the two-phase-commit protocol is delegated=20
   to the involved transaction managers. If the transaction commits,=20
   all orders have been successfully placed and the customer gets a=20
   positive acknowledgment. If the transaction aborts no orders will=20
   be placed and the customer will be informed of the problem.=20

   Transaction support greatly simplifies programming of these=20
   applications as exception handling and failure recovery are delegated
   to a special component. End users are also not left having to deal=20
   with the consequences of only partial success.

   While this example shows how the protocol can be used by HTTP=20
   servers, applications may use the protocol when accessing a remote
   database (e.g. via ODBC), or invoking remote services using other
   already existing protocols (e.g. RPC). The protocol makes it easy for
   applications in a heterogeneous network to participate in the same
   transaction, even if using different communication protocols.

3. Transactions

   "Transaction" is the term given to the programming model whereby
   computational work performed has atomic semantics. That is, either=20
   all work completes successfully and changes are made permanent (the=20
   transaction commits), or if any work is unsuccessful, changes are=20
   undone (the transaction aborts). The work comprising a transaction=20
   (unit of work), is defined by the application.

4. Connections

   The Transaction Internet Protocol (TIP) requires a reliable ordered
   stream transport with low connection setup costs. In an Internet (IP)
   environment, TIP operates over TCP, optionally using a protocol to=20
   multiplex light-weight connections over the same TCP connection.=20
  =20
Lyon, et al                                                     [Page 4]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   Transaction managers which share transactions establish a TCP=20
   connection. The protocol uses a different connection for each=20
   simultaneous transaction shared between two transaction managers.
   After a transaction has ended, the connection can be reused for=20
   a different transaction.
  =20
   Optionally, instead of associating a TCP connection with only a=20
   single transaction, two transaction managers may agree on a protocol
   to multiplex light-weight connections over the same TCP connection,
   and associate each simultaneous transaction with a separate light-
   weight connection. Using light-weight connections reduces latency
   and resource consumption associated with executing simultaneous=20
   transactions. Similar techniques as described here are widely used=20
   by existing transaction processing systems.  See Appendix A for an
   example of one such protocol.

   Note that although the TIP protocol itself is described only in terms
   of TCP, there is nothing to preclude the use of TIP with other
   transport protocols. However, it is up to the implementor to ensure
   the chosen transport provides equivalent semantics to TCP, and to map
   the TIP protocol appropriately.=20

5. Transaction Identifiers

   Unfortunately, there is no single globally-accepted standard for the
   format of a transaction identifier; there are various standard and
   proprietary formats.  Allowed formats for a TIP transaction=20
   identifier are described below in the section "TIP Uniform Resource
   Locators". A transaction manager may map its internal transaction
   identifiers into this TIP format in any manner it sees fit.
   Furthermore, each party in a superior/subordinate relationship gets
   to assign its own identifier to the transaction; these identifiers
   are exchanged when the relationship is first established.  Thus, a
   transaction manager gets to use its own format of transaction
   identifier internally, but it must remember a foreign transaction
   identifier for each superior/subordinate relationship in which it is
   involved.

6. Pushing vs. Pulling Transactions

   Suppose that some program on node "A" has created a transaction, and
   wants some program on node "B" to do some work as part of the
   transaction.  There are two classical ways that he does this,
   referred to as the "push" model and the "pull" model.

   In the "push" model, the program on A first asks his transaction
   manager to export the transaction to node B.  A's transaction manager
   sends a message to B's TM asking it to instantiate the transaction as
   a subordinate of A, and return its name for the transaction.  The
   program on A then sends a message to its counterpart on B on the
   order of "Do some work, and make it part of the transaction that your
   transaction manager already knows of by the name ...".  Because A's
   TM knows that it sent the transaction to B's TM, A's TM knows to
   involve B's TM in the two-phase commit process.

Lyon, et al                                                     [Page 5]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   In the "pull" model, the program on A merely sends a message to B on
   the order of "Do some work, and make it part of the transaction that
   my TM knows by the name ...".  The program on B asks its TM to enlist
   in the transaction.  At that time, B's TM will "pull" the transaction
   over from A.  As a result of this pull, A's TM knows to involve B's
   TM in the two-phase commit process.

   The protocol described here supports both the "push" and "pull"
   models.

7. Endpoint Identification

   In certain cases after connection failures, one of the parties of
   a connection may have a responsibility to re-establish a new=20
   connection to the other party in order to complete the=20
   two-phase-commit protocol. If the party that initiated the original=20
   connection needs to re-establish it, the job is easy: he merely=20
   establishes a connection in the same way that he originally did it.=20
   However, if the other party needs to re-establish the connection,=20
   he needs to know how to contact the initiator of the original=20
   connection. He gets this information in the following way:

   After a TCP connection has been established the initiating party
   issues an IDENTIFY command and supplies an endpoint identifier which
   is used to re-establish the connection if needed. If the initiating=20
   party does not supply an endpoint identifier on the IDENTIFY command,
   he must not perform any action which would require a connection to be
   re-established (e.g. perform recovery actions).

   An <endpoint identifier> as used in the IDENTIFY (and a few other)
   commands has one of the following formats:
      <dns name>
      <ip address>
      <dns name>:<port number>
      <ip address>:<port number>

   A <dns name> is a standard name, acceptable to the domain name
   service. It must be sufficiently qualified to be useful to the
   receiver of the command.

   An <ip address> is an IP address, in the usual form: four decimal
   numbers separated by period characters.

   The <port number> is a decimal number specifying the port at which
   the transaction manager is listening for requests to establish TCP
   connections.  Two standard transaction service port numbers are
   defined: 3372 for TLS secured connections, and 3371 for unsecured
   connections. If the port number is omitted from the endpoint=20
   identifier, and if the current connection is TLS secured, then the
   standard TLS secured transaction service port number is assumed;
   otherwise the standard unsecured transaction service port number is
   assumed. Likewise, if a port number is specified, then it must
   represent a port with the same security capabilities as the current
   connection (i.e. TLS or unsecured).

Lyon, et al                                                     [Page 6]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

8. TIP Uniform Resource Locators

   Transactions and transaction managers are resources associated=20
   with the TIP protocol. Transaction managers and transactions are=20
   located using TCP/IP endpoint identifiers. Once a TCP connection has=20
   been established, TIP commands may be sent to operate on transactions
   associated with the respective transaction managers.=20

   Applications which want to pull a transaction from a remote node
   must supply a reference to the remote transaction which allows
   the local transaction manager (i.e. the transaction manager pulling
   the transaction) to connect to the remote transaction
   manager and identify the particular transaction. Applications
   which want to push a transaction to a remote node must supply=20
   a reference to the remote transaction manager (i.e. the transaction
   manager to which the transaction is to be pushed), which allows the=20
   local transaction manager to locate the remote transaction=20
   manager.=20

   The TIP protocol defines a URL scheme [4] which allows applications=20
   and transaction managers to exchange references (i.e. TIP URLs) to=20
   transaction managers and transactions.

   A TIP URL takes the form:

      TIP://<host>[:<port>]/<transaction string>
=20
   where <host> is an IP address or a DNS name as defined above; and
   <port> is a valid TCP port number. <transaction string> may take one
   of two forms (standard or non-standard):

      i. "urn:" <NID> ":" <NSS>

         A standard transaction identifier, conforming to the proposed
         Internet Standard for Uniform Resource Names (URNs), as
         specified by RFC2141; where <NID> is the Namespace Identifier,
         and <NSS> is the Namespace Specific String. The Namespace ID
         determines the syntactic interpretation of the Namespace
         Specific String. The Namespace Specific String is a sequence of
         characters representing a transaction identifier (as defined by
         <NID>). The rules for the contents of these fields are
         specified by [7] (valid characters, encoding, etc.).

         This format of <transaction string> may be used to express
         global transaction identifiers in terms of standard
         representations. Examples for <NID> might be <iso> or <xopen>.
         e.g.

         TIP://123.123.123.123/urn:xopen:xid
     =20
      ii. <transaction identifier>
=20
         A sequence of printable ASCII characters (octets with values in
         the range 32 through 126 inclusive (excluding ":"))

Lyon, et al                                                     [Page 7]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

         representing a transaction identifier. In this non-standard
         case, it is the combination of <host> and
         <transaction identifier> which ensures global uniqueness. e.g.

         TIP://123.123.123.123/transid1     =20

   Except as otherwise described above, the TIP URL scheme follows the
   rules for reserved characters as defined in [4], and uses escape=20
   sequences as defined in [4] Section 5.=20

   Note that the TIP protocol itself does not use the TIP URL scheme.
   This URL scheme is proposed as a standard way to pass transaction
   identification information through other protocols. e.g. between
   cooperating application processes. The URL may then be used to
   communicate to the local transaction manager the information
   necessary to associate the application with a particular TIP
   transaction. e.g. to PULL the transaction from a remote transaction
   manager. It is anticipated that each TIP implementation will provide
   some set of APIs for this purpose.

   To create a non-standard TIP URL from a transaction identifier, first
   replace any reserved characters in the transaction identifier with
   their equivalent escape sequences, then insert the appropriate host
   endpoint identification. If the transaction identifier is one that
   you created, insert your own endpoint identification. If the
   transaction identifier is one that you received on a TIP connection
   that you initiated, insert the identification of the party to which
   you connected. If the transaction identifier is one that you received
   on a TIP connection that you did not initiate, use the identification
   that was received in the IDENTIFY command.

9. States of a Connection

   At any instant, only one party on a connection is allowed to send=20
   commands, while the other party is only allowed to respond to=20
   commands that he receives. Throughout this document, the party that
   is allowed to send commands is called "primary"; the other party is
   called "secondary". Initially, the party that initiated the=20
   connection is primary; however, a few commands cause the
   roles to switch. A connection returns to it's original polarity
   whenever the Idle state is reached.

   When multiplexing is being used, these rules apply independently to=20
   each "virtual" connection, regardless of the polarity of the
   underlying connection (which will be in the Multiplexing state).

   Note that commands may be sent "out of band" by the secondary via the
   use of pipelining. This does not affect the polarity of the
   connection (i.e. the roles of primary and secondary do not switch).=20
   See section 12 for details.

   At any instant, a connection is in one of the following states.
   From the point of view of the secondary party, the state changes when
   he sends a reply; from the point of view of the primary party, the

Lyon, et al                                                     [Page 8]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   state changes when he receives a reply.

   Initial: The initial connection starts out in the Initial state.=20
      Upon entry into this state, the party that initiated the=20
      connection becomes primary, and the other party becomes secondary.
      There is no transaction associated with the connection in this=20
      state. From this state, the primary can send the IDENTIFY command.

   Idle: In this state, the primary and the secondary have=20
      agreed on a protocol version, and the primary supplied an=20
      endpoint identifier to the secondary party to reconnect after=20
      a failure. There is no transaction associated with the=20
      connection in this state.  Upon entry to this state, the party
      that initiated the connection becomes primary, and the other
      party becomes secondary. From this state, the primary can send=20
      any of the following commands: BEGIN, MULTIPLEX, PUSH,  PULL,
      QUERY and RECONNECT.=20

   Begun: In this state, a connection is associated with an active
      transaction, which can only be completed by a one-phase protocol.
      A BEGUN response to a BEGIN command places a connection into=20
      this state. Failure of a connection in Begun state implies=20
      that the transaction will be aborted. From this state, the=20
      primary can send an ABORT, or COMMIT command.

   Enlisted: In this state, the connection is associated with an active
      transaction, which can be completed by a one-phase or, two-phase=20
      protocol. A PUSHED response to a PUSH command, or a PULLED=20
      response to a PULL command, places the connection into this state.
      Failure of the connection in Enlisted state implies that the=20
      transaction will be aborted. From this state, the primary can=20
      send an ABORT, COMMIT, or PREPARE command.

   Prepared: In this state, a connection is associated with a=20
      transaction that has been prepared. A PREPARED response to a=20
      PREPARE command, or a RECONNECTED response to a RECONNECT=20
      command places a connection into this state.  Unlike other=20
      states, failure of a connection in this state does not cause=20
      the transaction to automatically abort. From this state, the
      primary can send an ABORT, or COMMIT command.

   Multiplexing: In this state, the connection is being used by a
      multiplexing protocol, which provides its own set of connections.
      In this state, no TIP commands are possible on the connection.
      (Of course, TIP commands are possible on the connections
      supplied by the multiplexing protocol.) The connection can
      never leave this state.

   Error: In this state, a protocol error has occurred, and the
      connection is no longer useful.=20

10. Protocol Versioning

   This document describes version 2 of the protocol. In order to

Lyon, et al                                                     [Page 9]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   accommodate future versions, the primary party sends a message
   indicating the lowest and the highest version number it understands.=20
   The secondary responds with the highest version number it=20
   understands.=20
  =20
   After such an exchange, communication can occur using the smaller of
   the highest version numbers (i.e., the highest version number that=20
   both understand). This exchange is mandatory and occurs using the
   IDENTIFY command (and IDENTIFIED response).=20

   If the highest version supported by one party is considered obsolete
   and no longer supported by the other party, no useful communication
   can occur.  In this case, the newer party should merely drop the
   connection.

11. Commands and Responses

   All commands and responses consist of one line of ASCII text, using
   only octets with values in the range 32 through 126 inclusive,
   followed by either a CR (an octet with value 13) or an LR (an octet
   with value 10).  Each line can be split up into one or more "words",
   where successive words are separated by one or more space octets
   (value 32).

   Arbitrary numbers of spaces at the beginning and/or end of each line
   are allowed, and ignored.

   Lines that are empty, or consist entirely of spaces are ignored.
   (One implication of this is that you can terminate lines with both a
   CR and an LF if desired; the LF will be treated as terminating an
   empty line, and ignored.)

   In all cases, the first word of each line indicates the=20
   type of command or response; all defined commands and responses=20
   consist of upper-case letters only.

   For some commands and responses, subsequent words convey parameters
   for the command or response; each command and response takes a fixed
   number of parameters.

   All words on a command or response line after (and including) the=20
   first undefined word are totally ignored. These can be used to pass
   human-readable information for debugging or other purposes.

12. Command Pipelining

   In order to reduce communication latency and improve efficiency, it=20
   is possible for multiple TIP "lines" (commands or responses) to be=20
   pipelined (concatenated) together and sent as a single message. Lines =

   may also be sent "ahead" (by the secondary, for later procesing by=20
   the primary). Examples are an ABORT command immediately followed by a =

   BEGIN command, or a COMMITTED response immediately followed by a PULL =

   command.

  =20
Lyon, et al                                                    [Page 10]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   The sending of pipelined lines is an implementation option. Likewise
   which lines are pipelined together. Generally, it must be certain
   that the pipelined line will be valid for the state of the connection
   at the time it is processed by the receiver. It is the responsibility
   of the sender to determine this.

   All implementations must support the receipt of pipelined lines - the
   rules for processing of which are described by the following
   paragraph:

   When the connection state is such that a line should be read (either
   command or response), then that line (when received) is processed. No
   more lines are read from the connection until processing again=20
   reaches such a state. If a line is received on a connection when it's =

   not the turn of the other party to send, that line is _not_ rejected.
   Instead, the line is held and processed when the connection state
   again requires it. The receiving party must process lines and issue
   responses in the order of lines received. If a line causes an error
   the connection enters the Error state, and all subsequent lines on
   the connection are discarded.

13. TIP Commands

   Commands pertain either to connections or transactions. Commands
   which pertain to connections are: IDENTIFY and MULTIPLEX. Commands
   which pertain to transactions are: ABORT, BEGIN, COMMIT, PREPARE,=20
   PULL, PUSH, QUERY, and RECONNECT.

   Following is a list of all valid commands, and all possible responses
   to each:

   ABORT

      This command is valid in the Begun, Enlisted, and Prepared states.
      It informs the secondary that the current transaction of the
      connection will abort. Possible responses are:

      ABORTED=20
         The transaction has aborted; the connection enters Idle=20
         state.

      ERROR=20
         The command was issued in the wrong state, or was malformed.
         The connection enters the Error state.

   BEGIN

      This command is valid only in the Idle state. It asks the
      secondary to create a new transaction and associate it with the=20
      connection. The newly created transaction will be completed with a
      one-phase protocol. Possible responses are:

      BEGUN <transaction identifier>
         A new transaction has been successfully begun, and that

Lyon, et al                                                    [Page 11]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

         transaction is now the current transaction of the connection.
         The connection enters Begun state.

      NOTBEGUN=20
         A new transaction could not be begun; the connection=20
         remains in Idle state.

      ERROR=20
         The command was issued in the wrong state, or was malformed.
         The connection enters the Error state.

   COMMIT

      This command is valid in the Begun, Enlisted or Prepared states.=20
      In the Begun or Enlisted state, it asks the secondary to attempt=20
      to commit the transaction; in the Prepared state, it informs the=20
      secondary that the transaction has committed. Note that in the
      Enlisted state this command represents a one-phase protocol, and
      should only be done when the sender has 1) no local recoverable
      resources involved in the transaction, and 2) only one subordinate
      (the sender will not be involved in any transaction recovery=20
      process). Possible responses are:

      ABORTED=20
         This response is possible only from the Begun and Enlisted=20
         states. It indicates that some party has vetoed the commitment
         of the transaction, so it has been aborted instead of=20
         committing. The connection enters the Idle state.

      COMMITTED=20
         This response indicates that the transaction has been
         committed, and that the primary no longer has any
         responsibilities to the secondary with respect to the
         transaction. The connection enters the Idle state.

      ERROR=20
         The command was issued in the wrong state, or was malformed.
         The connection enters the Error state.

   ERROR=20

      This command is valid in any state; it informs the secondary that
      a previous response was not recognized or was badly formed.  A
      secondary should not respond to this command. The connection
      enters Error state.

   IDENTIFY  <lowest  protocol version>
             <highest protocol version>
             <initiating party's endpoint identifier> | "-"

      This command is valid only in the Initial state. The primary party
      informs the secondary party of the lowest and highest protocol=20
      version supported (all versions between the lowest and highest
      must be supported), and optionally of an IP address and a port=20
     =20
Lyon, et al                                                    [Page 12]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

      number at which the other party can re-establish a connection=20
      if ever needed. If the primary party does not supply an endpoint=20
      identifier the secondary party will respond with ABORTED or=20
      READONLY to any PREPARE commands. Possible responses are:

      IDENTIFIED <protocol version>
         The accepting party has saved the identification. The response
         contains the highest protocol version supported by the
         secondary party. All future communication is assumed to take=20
         place using the smaller of the protocol versions in the=20
         IDENTIFY command and the IDENTIFIED response. The connection
         enters the Idle state.=20

      ERROR=20
         The command was issued in the wrong state, or was malformed.
         This response also occurs if the accepting party does not
         support any version of the protocol in the range supported
         by the initiator. The connection enters the Error state. The
         initiator should close the connection.

   MULTIPLEX  <protocol-identifier>

      This command is only valid in the Idle state. The command=20
      seeks agreement to use the connection for a multiplexing
      protocol that will supply a large number of connections on
      the existing connection. The primary suggests a particular
      multiplexing protocol. The secondary party can either accept
      or reject use of this protocol.

      At the present, the only defined protocol identifier is "TMP2.0",
      which refers to the TIP Multiplexing Protocol, version 2.0. See
      Appendix A for details of this protocol. Other protocol=20
      identifiers may be defined in the future.

      If the MULTIPLEX command is accepted, the specified multiplexing
      protocol will totally control the underlying connection. This
      protocol will begin with the first byte after the line terminator
      of the MULTIPLEX command (for data sent by the initiator),
      and the first byte after the line terminator of the MULTIPLEXING
      response (for data received by the initiator). This implies that
      an implementation must not send both a CR and a LF octet after
      either the MULTIPLEX command or the MULTIPLEXING response, lest
      the LF octet be mistaken for the first byte of the multiplexing
      protocol.

      Note that when using TMP V2.0, a single TIP command (TMP
      application message) must be wholly contained within a single TMP
      packet (the TMP PUSH flag is not used by TIP).

      Possible responses to the MULTIPLEX command are:

      MULTIPLEXING
         The secondary party agrees to use the specified multiplexing
         protocol. The connection enters the Multiplexing state, and
        =20
Lyon, et al                                                    [Page 13]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

         all subsequent communication is as defined by that protocol.
         All connections created by the multiplexing protocol start
         out in the Idle state.=20

      CANTMULTIPLEX
         The secondary party cannot support (or refuses to use) the
         specified multiplexing protocol. The connection remains in the
         Idle state.

      ERROR
         The command was issued in the wrong state, or was malformed.
         The connection enters the Error state.

   PREPARE=20

      This command is valid only in the Enlisted state; it requests=20
      the secondary to prepare the transaction for commitment (phase
      one of two-phase commit). Possible responses are:

      PREPARED=20
         The subordinate has prepared the transaction; the connection
         enters PREPARED state.

      ABORTED=20
         The subordinate has vetoed committing the transaction. The
         connection enters the Idle state.  After this response, the=20
         superior has no responsibilities to the subordinate with=20
         respect to the transaction.

      READONLY=20
         The subordinate no longer cares whether the transaction
         commits or aborts. The connection enters the Idle state. After
         this response, the superior has no responsibilities to the=20
         subordinate with respect to the transaction.

      ERROR=20
         The command was issued in the wrong state, or was malformed.
         The connection enters the Error state.

   PULL  <superior's transaction identifier>
         <subordinate's transaction identifier>

      This command is only valid in Idle state. This command seeks to=20
      establish a superior/subordinate relationship in a transaction,=20
      with the primary party of the connection as the subordinate (i.e., =

      he is pulling a transaction from the secondary party). Note that
      the entire value of <transaction string> (as defined in the=20
      section "TIP Uniform Resource Locators") must be specified as the
      transaction identifier. Possible responses are:

      PULLED=20
         The relationship has been established.  Upon receipt of this
         response, the specified transaction becomes the current
         transaction of the connection, and the connection enters=20
        =20
Lyon, et al                                                    [Page 14]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

         Enlisted state. Additionally, the roles of primary and=20
         secondary become reversed.  (That is, the superior becomes=20
         the primary for the connection.)

      NOTPULLED=20
         The relationship has not been established (possibly, because
         the secondary party no longer has the requested transaction).
         The connection remains in Idle state.

      ERROR=20
         The command was issued in the wrong state, or was malformed.
         The connection enters the Error state.

   PUSH <superior's transaction identifier>

      This command is valid only in the Idle state. It seeks to=20
      establish a superior/subordinate relationship in a transaction=20
      with the primary as the superior. Note that the entire value of
      <transaction string> (as defined in the section "TIP Uniform
      Resource Locators") must be specified as the transaction
      identifier. Possible responses are:

      PUSHED <subordinate's transaction identifier>
         The relationship has been established, and the identifier by
         which the subordinate knows the transaction is returned.  The=20
         transaction becomes the current transaction for the connection, =

         and the connection enters Enlisted state.

      ALREADYPUSHED <subordinate's transaction identifier>
         The relationship has been established, and the identifier by
         which the subordinate knows the transaction is returned.
         However, the subordinate already knows about the transaction,
         and is expecting the two-phase commit protocol to arrive via a
         different connection. In this case, the connection remains in
         the Idle state.

      NOTPUSHED=20
         The relationship could not be established. The connection
         remains in the Idle state.

      ERROR=20
         The command was issued in the wrong state, or was malformed.
         The connection enters Error state.

   QUERY <superior's transaction identifier>

      This command is valid only in the Idle state. A subordinate uses
      this command to determine whether a specific transaction still=20
      exists at the superior. Possible responses are:

      QUERIEDEXISTS=20
         The transaction still exists.  The connection remains in the=20
         Idle state.

     =20
Lyon, et al                                                    [Page 15]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

      QUERIEDNOTFOUND=20
         The transaction no longer exists.  The connection remains in
         the Idle state.

      ERROR
         The command was issued in the wrong state, or was malformed.
         The connection enters Error state.

   RECONNECT <subordinate's transaction identifier>

      This command is valid only in the Idle state. A superior uses the=20
      command to re-establish a connection for a transaction, when the=20
      previous connection was lost during Prepared state. Possible=20
      responses are:

      RECONNECTED=20
         The subordinate accepts the reconnection. The connection enters
         Prepared state.

      NOTRECONNECTED=20
         The subordinate no longer knows about the transaction. The=20
         connection remains in Idle state.

      ERROR=20
         The command was issued in the wrong state, or was malformed.
         The connection enters Error state.

14. Error Handling

   If either party receives a line that it cannot understand it closes
   the connection. If either party (either a command or a response),=20
   receives an ERROR indication or an ERROR response on a connection=20
   the connection enters the Error state and no further communication=20
   is possible on that connection. An implementation may decide to=20
   close the connection. Closing of the connection is treated by the=20
   other party as a communication failure.=20

   Receipt of an ERROR indication or an ERROR response indicates that=20
   the other party believes that you have not properly implemented the=20
   protocol.=20
  =20
15. Connection Failure and Recovery

   A connection failure may be caused by a communication failure, or by
   any party closing the connection. Depending on the state of a=20
   connection, transaction managers will need to take various actions
   when a connection fails.

   If the connection fails in Initial or Idle state, the connection does =

   not refer to a transaction. No action is necessary.

   If the connection fails in the Multiplexing state, all connections
   provided by the multiplexing protocol are assumed to have failed.
   Each of them will be treated independently.

Lyon, et al                                                    [Page 16]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   If the connection fails in Begun or Enlisted state and COMMIT has=20
   been sent, then transaction completion has been delegated to the=20
   subordinate (the superior is not involved); the outcome of the=20
   transaction is unknown by the superior (it is known at the=20
   subordinate). The superior uses application-specific means to=20
   determine the outcome of the transaction (note that transaction
   integrity is not compromised in this case since the superior has no
   recoverable resources involved in the transaction). If the connection
   fails in Begun or Enlisted state and COMMIT has not been sent, the
   transaction will be aborted.

   If the connection fails in Prepared state, then the appropriate
   action is different for the superior and subordinate in the
   transaction.

   If the superior determines that the transaction commits, then it
   must eventually establish a new connection to the subordinate, and
   send a RECONNECT command for the transaction. If it receives a
   NOTRECONNECTED response, it need do nothing else. However, if it
   receives a RECONNECTED response, it must send a COMMIT request and
   receive a COMMITTED response.

   If the superior determines that the transaction aborts, it is allowed
   to (but not required to) establish a new connection and send a=20
   RECONNECT command for the transaction. If it receives a RECONNECTED=20
   response, it should send an ABORT command.

   The above definition allows the superior to reestablish the=20
   connection before it knows the outcome of the transaction, if it=20
   finds that  convenient. Having succeeded in a RECONNECT command,=20
   the connection is back in Prepared state, and the superior can send a =

   COMMIT or ABORT command as appropriate when it knows the transaction=20
   outcome.

   If a subordinate notices a connection failure in Prepared state, then
   it should periodically attempt to create a new connection to the
   superior and send a QUERY command for the transaction. It should
   continue doing this until one of the following two events occurs:

   1. It receives a QUERIEDNOTFOUND response from the superior. In this
      case, the subordinate should abort the transaction.

   2. The superior, on some connection that it initiated, sends a
      RECONNECT command for the transaction to the subordinate. In this
      case, the subordinate can expect to learn the outcome of the
      transaction on this new connection. If this new connection should
      fail before the subordinate learns the outcome of the transaction,
      it should again start sending QUERY commands.

   Note that if a TIP system receives either a QUERY or a RECONNECT
   command, and for some reason is unable to satisfy the request (e.g.=20
   the necessary recovery information is not currently available), then
   the connection should be dropped.


Lyon et al                                                     [Page 17]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

16. Security Considerations

   As with all two phase-commit protocols, any security mechanisms
   applied to the application communication protocol are liable to be
   subverted unless corresponding mechanisms are applied to the
   commitment protocol. For example, any authentication between the
   parties using the application protocol must be supported by security
   of the TIP exchanges to at least the same level of certainty.
  =20
   If a system does not protect itself through usage of another protocol
   such as the Transport Layer Security protocol, then security
   implications fall into the following categories:

   1. Someone PUSHED a new transaction to us that we don't want.
      Depending on his correctness or intentions, he may or may not ever
      complete it. Thus, an arbitrary computer may cause us to save a
      little bit of state. An implementation concerned about this will
      probably drop the TCP connection if the other system does not=20
      complete transactions in a timely manner.=20
     =20
      The Transport Layer Security protocol [3] may be used by a
      transaction manager to restrict access to trusted clients only.=20

   2. Someone PULLED a transaction from us when we didn't want him to.
      In this case, he will become involved in the atomic commitment
      protocol. At worst, he may cause a transaction to abort that
      otherwise would have committed.  Since transaction managers
      traditionally reserve the right to abort any transaction for any
      reason they see fit, this does not represent a disaster to the
      applications. However, if done frequently, it may represent a
      denial-of-service attack.=20

      Implementations concerned about this kind of attack can use the=20
      Transport Layer Security protocol [3] to restrict access to
      trusted partners (i.e. to control from which remote endpoints
      TIP transactions will be accepted, and to verify that an end-point
      is genuine), and encrypt TIP commands thus preventing unauthorized
      disclosure of transaction identifiers.

   3. Someone violates the TIP commitment protocol. (e.g. a COMMIT
      command is injected on a TIP connection in place of an ABORT
      command). This yields the possibility of data inconsistency.

      Implementations concerned about this kind of attack can also use
      the Transport Layer Security protocol [3] to restrict access to
      only trusted partners and to encrypt TIP commands.

   It is assumed that implementation-specific configuration information
   will define whether a partner should be connected to using either a
   mandatory TLS secured connection, or an unsecured connection (in=20
   which case any security risk is accepted). "Optionally TLS secured"=20
   is in effect unsecured (since there is no guarantee of a TLS secured
   connection).


Lyon, et al                                                    [Page 18]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

17. Significant changes from previous version of this Internet-Draft
    (<draft-lyon-itp-nodes-02.txt>):

   None (minor editorial changes to aid understanding and fix errors).

References

   [1]  Gray, J. and A. Reuter (1993), Transaction Processing: Concepts
        and Techniques.  San Francisco, CA: Morgan Kaufmann Publishers.
        (ISBN 1-55860-190-2).

   [2]  RFC2068 Standards Track "Hypertext Transfer Protocol --
        HTTP/1.1".
        R. Fielding et al.

   [3]  Internet-Draft "The TLS Protocol Version 1.0".
        T. Dierks et al.

   [4]  RFC1738 Standards Track "Uniform Resource Locators (URL)".
        T. Berners-Lee et al.

   [5]  Internet-Draft "Transaction Internet Protocol - Requirements and
        Supplemental Information".
        K. Evans et al.

   [6]  Internet-Draft "Session Control Protocol V 2.0".
        K. Evans et al.

   [7]  RFC2141 "URN Syntax".
        R. Moats.

Authors' Addresses

   Jim Lyon                           Keith Evans
   Microsoft Corporation              Tandem Computers, Inc.
   One Microsoft Way                  5425 Stevens Creek Blvd
   Redmond, WA  98052-6399, USA       Santa Clara, CA 95051-7200, USA

   Phone: +1 (206) 936 0867           Phone: +1 (408) 285 5314
   Fax:   +1 (206) 936 7329           Fax:   +1 (408) 285 5245
   Email: JimLyon@Microsoft.Com       Email: Keith@Loc252.Tandem.Com

   Johannes Klein
   Tandem Computers Inc.
   10555 Ridgeview Court
   Cupertino, CA 95014-0789, USA

   Phone: +1 (408) 285 0453
   Fax:   +1 (408) 285 9818
   Email: Klein_Johannes@Tandem.Com

Comments

   Please send comments on this document to the authors at=20
  =20
Lyon, et al                                                    [Page 19]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   <JimLyon@Microsoft.Com>, <Keith@Loc252.Tandem.Com>,
   <Klein_Johannes@Tandem.Com>, or to the TIP mailing list at
   <Tip@Tandem.Com>. You can subscribe to the TIP mailing list by
   sending mail to <Listserv@Tandem.Com> with the line "subscribe tip"=20
   somewhere in the body of the message.


















































Lyon, et al                                                    [Page 20]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

Appendix A. The TIP Multiplexing Protocol Version 2.0.

   This appendix describes version 2.0 of the TIP Multiplexing Protocol
   (TMP). TMP V2.0 is the same as the Session Control Protocol (SCP)
   version 2.0, as described by [6]. TMP is intended solely for use
   with the TIP protocol, and forms part of the TIP protocol
   specification (although its implementation is optional), hence its
   inclusion in this document. TMP V2.0 is the only multiplexing=20
   protocol supported by TIP V2.0. The following text is a copy of [6]
   with no substantive changes, it is edited only as necessary to
   reflect the name change and for inclusion in this document.=20

Abstract=20

   TMP provides a simple mechanism for creating multiple lightweight=20
   connections over a single TCP connection. Several such lightweight
   connections can be active simultaneously. TMP provides a byte=20
   oriented service, but allows message boundaries to be marked.=20

A.1. Introduction=20

   There are several protocols in widespread use on the Internet which
   create a single TCP connection for each transaction. Unfortunately,
   because these transactions are short lived, the cost of setting up
   and tearing down these TCP connections becomes significant, both in
   terms of resources used and in the delays associated with TCP's
   congestion control mechanisms.=20

   The TIP Multiplexing Protocol (TMP) is a simple protocol running on
   top of TCP that can be used to create multiple lightweight=20
   connections over a single transport connection. TMP therefore
   provides for more efficient use of TCP connections. Data from
   several different TMP connections can be interleaved, and both
   message boundaries and end of stream markers can be provided.=20
=20
   Because TMP runs on top of a reliable byte ordered transport
   service it can avoid most of the extra work TCP must go through in
   order to ensure reliability. For example, TMP connections do not
   need to be confirmed, so there is no need to wait for handshaking
   to complete before data can be sent.

A.2. Protocol Model=20

   The basic protocol model is that of multiple lightweight
   connections operating over a reliable stream of bytes. The party
   which initiated the connection is referred to as the primary, and
   the party which accepted the connection is referred to as the
   secondary.
  =20
   Connections may be unidirectional or bi-directional; each end of a
   bi-directional connection may be closed separately. Connections may
   be closed normally, or reset to indicate an abortive release.
   Aborting a connection closes both data streams.=20

  =20
Lyon, et al                                                    [Page 21]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   Once a connection has been opened, applications can send messages
   over it, and signal the end of application level messages.
   Application messages are encapsulated in TMP packets and
   transferred over the byte stream. A single TIP command (TMP
   application message) must be wholly contained within a single TMP
   packet.

A.3. TMP Packet Format=20

   A TMP packet consists of a 64 bit header followed by zero or more
   octets of data. The header contains three fields; a flag byte, the
   connection identifier, and the packet length. Both integers, the
   connection identifier and the packet length must be sent in network
   byte order.=20

    FLAGS
   +--------+--------+--------+--------+
   |SFPR0000| Connection ID            |
   +--------+--------+--------+--------+
   |        | Length                   |
   +--------+--------+--------+--------+=20

   A.3.1. Flag Details

      +-------+-----------+-----------------------------------------+
      | Name  | Mask      | Description                             |
      +-------+-----------+ ----------------------------------------+=20
      | SYN   | 1xxx|0000 | Open a new connection                   |
      | FIN   | x1xx|0000 | Close an existing connection            |
      | PUSH  | xx1x|0000 | Mark application level message boundary |
      | RESET | xxx1|0000 | Abort the connection                    |=20
      +-------+-----------+-----------------------------------------+

A.4. Connection Identifiers=20
 =20
   Each TMP connection is identified by a 24 bit integer. TMP
   connections created by the party which initiated the underlying TCP=20
   connection must have even identifiers; those created by the other
   party must have odd identifiers.=20

A.5. TMP Connection States=20

   TMP connections can exist in several different states; Closed,
   OpenWrite, OpenSynRead, OpenSynReset, OpenReadWrite, CloseWrite,
   and CloseRead. A connection can change its state in response to
   receiving a packet with the SYN, FIN, or RESET bits set, or in
   response to an API call by the application. The available API calls
   are open, close, and abort.=20

   The meaning of most states is obvious (e.g. OpenWrite means that a
   connection has been opened for writing). The meaning of the states
   OpenSynRead and OpenResetRead need more explanation.

   In the OpenSynRead state a primary opened and immediately closed the
  =20
Lyon, et al                                                    [Page 22]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   output data stream of a connection, and is now waiting for a SYN
   response from the secondary to open the input data stream for=20
   reading.=20

   In the OpenResetRead state a primary opened and immediately aborted
   a connection, and is now waiting for a SYN response from the=20
   secondary to finally close the connection.

A.6. Event Priorities and State Transitions=20

   The state table shown below describes the actions and state
   transitions that occur in response to a given event. The events
   accepted by each state are listed in priority order with highest
   priority first. If multiple events are present in a message, those
   events matching the list are processed. If multiple events match,
   the event with the highest priority is accepted and processed
   first. Any remaining events are processed in the resultant
   successor state.=20

   For example, if a TMP connection at the secondary is in the Closed
   state, and the secondary receives a packet containing a SYN event, a
   FIN event and an input data event (i.e. DATA-IN), the secondary first
   accepts the SYN event (because it is the only match in Closed
   state). The secondary accepts the connection, sends a SYN event and
   enters the ReadWrite state. The SYN event is removed from the list
   of pending events. The remaining events are FIN and DATA-IN. In the
   ReadWrite state the secondary reads the input data (i.e. the DATA-IN
   event is processed first because it has higher priority than the
   FIN event). Once the data has been read and the DATA-IN event has
   been removed from the list of pending events, the FIN event is
   processed and the secondary enters the CloseWrite state.

   If either party receives a TMP packet that it does not understand,
   or an event in an incorrect state, it closes the TCP connection.





















Lyon, et al                                                    [Page 23]


=0C
INTERNET-DRAFT                 TIP Version 2.0                  Oct 1997

   =
+=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D+=3D=3D=3D=3D=3D=3D=3D=3D=3D+=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D+=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D+
   | Entry State  | Event   | Action   | Exit State   |
   =
+=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D+=3D=3D=3D=3D=3D=3D=3D=3D=3D+=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D+=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D+
   | Closed       | SYN     | SYN      | ReadWrite    |
   |              | OPEN    | SYN      | OpenWrite    |
   +--------------+---------+----------+--------------+
   | OpenWrite    | SYN     | Accept   | ReadWrite    |
   |              | WRITE   | DATA-OUT | OpenWrite    |
   |              | CLOSE   | FIN      | OpenSynRead  |
   |              | ABORT   | RESET    | OpenSynReset |
   +--------------+---------+----------+--------------+
   | OpenSynRead  | SYN     | Accept   | CloseRead    |
   +--------------+---------+----------+--------------+
   | OpenSynReset | SYN     | Accept   | Closed       |
   +--------------+---------+----------+--------------+
   | ReadWrite    | DATA-IN | Accept   | ReadWrite    |
   |              | FIN     | Accept   | CloseWrite   |
   |              | RESET   | Accept   | Closed       |
   |              | WRITE   | DATA-OUT | ReadWrite    |
   |              | CLOSE   | FIN      | CloseRead    |
   |              | ABORT   | RESET    | Closed       |
   +--------------+---------+----------+--------------+
   | CloseWrite   | RESET   | Accept   | Closed       |
   |              | WRITE   | DATA-OUT | CloseWrite   |
   |              | CLOSE   | FIN      | Closed       |
   |              | ABORT   | RESET    | Closed       |
   +--------------+---------+----------+--------------+
   | CloseRead    | DATA-IN | Accept   | CloseRead    |
   |              | FIN     | Accept   | Closed       |
   |              | RESET   | Accept   | Closed       |
   |              | ABORT   | RESET    | Closed       |
   +--------------+---------+----------+--------------+

        TMP Event Priorities and State Transitions=20





















Lyon, et al                                                    [Page 24]