rfc2188.txt

<VC++网络游戏建摸与实现>源代码

2.6.3  Error-argument

   This parameter provides additional information about the error in
   reply to a previous ESROS-INVOKE.indication in the case of an
   unsuccessfully performed operation.  The type (if any) has to be
   agreed between the ESROS users.  This parameter has to be supplied by
   the ESROS Performer User.  Encoding type of the Error-argument is
   specified through the Error-argument-encoding-type parameter (see
   previous subsection).





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RFC 2188                          ESRO                    September 1997


                  Invoker        Performer
                 ESROS AP         ESROS AP
                       |               |
                       |               |
   ESROS-FAILURE.ind.  |               |
   --------<-----------|               |
                       |               |
                       |               | ESROS-FAILURE.ind.
                       |               |--------->---------
                       |               |


   Figure 6:  Time sequence diagram for ESROS-FAILURE service




   ESROS Performer User provides the Error-argument parameter for the
   ESROS-ERROR.request primitive.  The Error-argument parameter of
   ESROS-ERROR.indication is provided to the ESROS Invoker User.

2.6.4  Invoke-ID

   This parameter identifies the corresponding invocation.  This
   Invoke-ID, which is originally generated by the ESROS provider at the
   time of the ESROS-INVOKE.indication, is extracted from the Invoke ID
   which has to be supplied by the ESROS performer User.  The value is
   that of the corresponding ESROS-INVOKE.indication primitive.

2.6.5  Failure-value

   This parameter identifies the failure that occurred during the
   processing or transmission of any of the service primitives of ESROS.
   This parameter has to be supplied by the ESROS provider (see also
   Section 2.7).

2.7  ESROS-FAILURE Service

   The ESROS-FAILURE service is used by ESROS provider to indicate the
   failure in providing an ESROS-INVOKE, ESROS-RESULT, or ESROS-ERROR
   service.

   The related service structure consists of one service primitive as
   illustrated in Figure 6 and Table 8.







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          _____________________________________________
          | Primitive                |Parameters       |
          |__________________________|_________________|
          |                          |Failure-value    |
          | ESROS-FAILURE.indication |Invoke-ID        |
          |__________________________|_________________|



   Table 8:  ESROS-FAILURE service primitives and associated parameters


          _________________________________________
          | Failure Value |Meaning                 |
          |_______________|________________________|
          | 0             |Transmission failure    |
          | 1             |Out of local resources  |
          | 2             |User not responding     |
          | 3             |Out of remote resources |
          | 4             |Reassembly failure      |
          |_______________|________________________|


             Table 9:  Encoding of Failure-value

2.7.1  Failure-value

   This parameter identifies the failure that occurred during the
   processing or transmission of any of the service primitives of ESROS.
   This parameter has to be supplied by the ESROS provider.

   The values for encoding of Failure-value are presented in Table 9.

2.7.2  Invoke-ID

   This parameter identifies the corresponding invocation.  This
   Invoke-ID, which is originally generated by ESROS provider at the
   time of the ESROS-INVOKE.indication, is extracted from the Invoke ID
   which has to be supplied by ESROS performer User.  The value is that
   of the corresponding ESROS-INVOKE.indication primitive.

3  ESRO SERVICE NOTATION

   Users of ESRO services (invoker and performer) need to agree on a
   well defined set of parameters which are enumerated below.

    1. The operation's Argument data type.




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    2. The operation's Result data type.

    3. The operation's Error data type.

    4. The operation's value.  A specific tag which uniquely identifies
        the operation.

   The invoker and the performer can specify these parameters using a
   variety of mechanisms.  The notation specified in this section is one
   such mechanism.  It is not the only machanism and ESRO protocol can
   be used independent of this notation.

3.1  ES-OPERATION Notation

   The Remote Operations and Operation Errors are specified in this
   section.  The notation is defined by means of the macro facility
   defined in [3].

   The macros enabling the specification of operations and errors are
   listed in Figure 7.

   Note that this notation is very similar to the abstract operation
   defined in [1].  The value form of ES-OPERATION is always an integer.

3.2  Mapping of ESROS Notation

3.2.1  Invocation of an Operation

   An operation is mapped onto the ESRO Services.

   The invocation of an operation is mapped on the ESRO-INVOKE service.

   The value assigned to the operation is mapped on the Operation-value
   parameter of that service.  The value of the Named-Type in the
   ARGUMENT clause of the OPERATION Macro is mapped on the Argument
   parameter of that service.

3.2.2  Reply of an Operation

   If an operation was successfully performed, the reply is mapped on
   the ESRO-RESULT service.

   The value of the Named-Type in the RESULT clause of the OPERATION

   DEFINITIONS ::=
   BEGIN
     ES-OPERATION, ERROR;
     -- macro definition for operations



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     ES-OPERATION MACRO ::=
     BEGIN
           TYPE NOTATION   ::=     Argument Result Errors
           VALUE NOTATION  ::=     value (localValue INTEGER)
           Argument        ::=     "ARGUMENT" NamedType | empty
           Result          ::=     "RESULT" ResultType | empty
           ResultType      ::=     NamedType | empty
           Errors          ::=     "ERRORS" "{"ErrorNames"}" | empty
           ErrorNames      ::=     ErrorList | empty
           ErrorList       ::=     Error | ErrorList "," Error
           Error           ::=     value (ERROR) | type
           NamedType       ::=     identifier type | type
     END
     -- macro definition for operations errors
     ERROR MACRO   ::=
     BEGIN
           TYPE NOTATION   ::=     Parameter
           VALUE NOTATION  ::=     value (localValue INTEGER)
           Parameter       ::=     "PARAMETER" NamedType | empty
           NamedType       ::=     identifier type | type
     END
   END


            Figure 7:  ES Remote Operation Notation

   macro is mapped on the Result parameter of that service.

   If an operation was not successfully performed, the reply is mapped
   on the ESRO-ERROR service.

   In this case one of the errors in the Identifier List of Error Names
   in the ERROR clause of the OPERATION macro may be applied.  The value
   assigned to the applied error is mapped onto the Error parameter of
   that service.  The value of the Named-Type in the PARAMETER clause of
   the ERROR macro of the applied error is mapped on the Error-
   parameter of that service.

4  REMOTE OPERATIONS PROTOCOL

4.1  Overview of the Protocol

   The ESROS protocol realizes the services defined in the section
   entitled ESROS Service Definitions.  Short operations are performed
   in a highly efficient manner.  The protocol operation is summarized
   below and is described in detail in the following sections.





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   Two Functional Units are defined which realize the services with 2-
   Way handshake and 3-Way handshake, called 2-Way Handshake Functional
   Unit and 3-Way Handshake Functional Unit respectively.

   The procedures specified in this section refer to Protocol Data Units
   (PDUs) which are defined in Section 4.4.

4.1.1  Service Provision (Invoker User)

      o An ESROS user binds to an ESRO Service Access Point (SAP) and
        specifies whether 3-Way or 2-Way handshake Functional Unit is to
        be associated with the SAP.

      o An ESROS user initiates the transfer of a PDU using the INVOKE
        service.

      o On receipt of an ESROS-INVOKE.request service primitive from the
        ESROS user:

            -- The ESROS provider generates an Invoke ID,

            -- Communicates the Invoke-ID to the invoker of the service
                   through the ESROS-INVOKE-P.confirm primitive,

4.1.2  Service Provision (Performer User)

      o An ESROS user binds to an ESRO Service Access Point (SAP) and
        specifies whether 3-Way or 2-Way handshake Functional Unit is to
        be associated with the SAP.

      o On receipt of an ESRO-INVOKE-PDU, the ESROS provider issues an
        ESROS-INVOKE.indication to the ESROS performer user.

      o On receipt of ESROS-RESULT.request or ESROS-ERROR.request from
        the performer, the provider creates the ESRO-RESULT-PDU or
        ESRO-ERROR-PDU.

      o In the case that the provider receives an ESRO-ACK-PDU for the
        transmitted ESRO-RESULT-PDU or ESRO-ERROR-PDU, if the
        corresponding SAP is associated with the 3-Way Handshake
        Functional Unit, it passes an ESROS-RESULT.confirm or ESROS-
        ERROR.confirm to the performer user.  If the corresponding SAP
        is associated with the 2-Way handshake Functional Unit, the
        ESRO-ACK-PDU is dropped as an invalid PDU.

      o In the case that the provider is not able to deliver the
        ESRO-RESULT-PDU or ESRO-ERROR-PDU, it issues an ESROS-
        FAILURE.indication to the performer user.  In the case that the



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        performer's SAP is associated with the 3-Way handshake
        Functional Unit and provider doesn't receive the ESRO-ACK-PDU
        for a transmitted ESRO-RESULT-PDU or an ESRO-ERROR-PDU, it
        passes an ESROS- FAILURE.indication to the performer user.

      o In the case that the performer's SAP is associated with the
        3-Way handshake Functional Unit and provider receives an ESRO-
        ACK-PDU for the operation, it passes an ESROS-RESULT.confirm or
        ESROS-ERROR.confirm.  In the case that the performer's SAP is
        associated with a 2-Way handshake Functional Unit and provider
        doesn't receive duplicate ESROS-INVOKE-PDUs from the invoker, it
        passes an ESROS-RESULT.confirm or ESROS-ERROR.confirm.

      o On receipt of an ESRO-FAILURE-PDU, the ESROS provider issues an
        ESROS-FAILURE.indication to the ESROS performer user.

4.2  Protocol Procedures

4.2.1  Service Access Point (SAP) Bind Procedure

   To access the ESRO Services, an ESROS user binds to an ESRO Service
   Access Point and specifies the SAP to be associated with 3-Way
   handshake Functional Unit or 2-Way handshake Functional Unit.  ESROS
   provider generates a SAP descriptor which is passed to the user.  The
   handshaking for all Invoke.requests addressed to that SAP and all
   PDUs addressed to that SAP will be either 3-Way or 2-Way based on the
   Functional Unit associated with SAP and specified by user at SAP bind
   time.

   It is the responsibility of the ESROS peer users (invoker and
   performer) to address their operations to the appropriate SAP (3-Way
   or 2-Way) based on the agreement between users.

4.2.2  Invoke Service Procedure

   An ESROS user initiates the transfer of a PDU using the INVOKE
   service.

   On receipt of an ESRO-INVOKE-PDU, the ESROS provider sends an ESROS-
   INVOKE.indication primitive to the ESROS performer user.

4.2.3  Invoke ID Assignment Procedure

   On receipt of an ESROS-INVOKE.request primitive from the ESROS user,
   the ESROS provider generates two invoke identifiers: