rfc929.txt

RFC 相关的技术文档

         some protocols (e.g., the intermediate mediation level
         discussed above for Telnet).  The default value for this
         parameter is 9.  The control flag for this parameter is -m.

      Transmit Response Discipline

         The Transmit Response Discipline parameter is used to set the
         desired action on the OPE's part for generating responses to
         Transmit commands.  Essentially the parameter determines when
         the OPE's response to the transmit command occurs (i.e.,
         immediately or delayed).

         The Transmit Response Discipline value is represented by a
         single ASCII character.  The character "N" is used for
         nonblocking Transmit commands, which implies that responses for
         Transmit commands should be generated as soon as the command
         has been examined for correctness (i.e., that the syntax is
         good and the parameters appear reasonable).  In other words,
         the outboard protocol interpreter has the data in its queue,
         but hasn't necessarily transmitted it to the net.  The
         character "B" is used for blocking Transmit commands, which
         requests that the response not be generated until the protocol
         interpreter has successfully transmitted the data (unless, of
         course, the Transmit command was badly formed). The default
         value for this parameter is "N", or a nonblocking Transmit
         command.  The control flag for this parameter is -tr.
         (Depending on the protocol in play, "successfully transmitted"
         might well imply that an acknowledgment of some sort has been
         received from the foreign Host, but for other protocols it
         might only mean that the given collection of bits has been
         passed from the OPE to the proximate net.)

      Foreign Address Secondary Component

         The addressing mechanisms supported by this level of H-FP are
         discussed above.  The Foreign Address Secondary Component
         parameter contains the value of the destination address's
         secondary component.  Some protocols do not require this
         parameter, or can obtain it from other information.  Therefore,
         the default value for this parameter is NULL.  A NULL secondary
         component might be an error for some protocols, however.  The
         secondary component can be expressed either numerically or
         symbolically.  The control flag for this parameter is -fs.
         (Note that it is intended to be "legal" to specify a Secondary
         Component other than the Well-Known Socket for the protocol in
         play; in such cases, the result should be that the virtualizing
         of the given protocol be applied to the stream, in the


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RFC 929                                                    December 1984
Proposed Host-Front End Protocol


         expectation that that's what the other side is expecting.  This
         is to cater to, for example, a Terminal-Terminal protocol that
         merely "does Telnet" to a socket other than the usual Logger.)

      Local Address Secondary Component

         The Local Address Secondary Component parameter contains the
         value of the local address's secondary component.  (The primary
         component is assumed to be the default for the Host, but can be
         altered as well; see below.) Some protocols do not require this
         parameter, or can obtain it from other information.  In some
         cases, the OPE may already know the value for this parameter
         and therefore not require it. The default value of this
         parameter is NULL.  The local address secondary component can
         be expressed either numerically or symbolically.  The control
         flag for this parameter is -ls.

      Begin Timeout Interval

         After a Begin command is issued, a timer can be started.  If
         the activity requested cannot be performed within some timed
         interval, then the Begin command may expire.  An expired Begin
         command returns a response code indicating a Begin timeout
         occurred.  The Begin Timeout Interval parameter contains the
         length of time the timer will run before the Begin timeout
         occurs.

         The parameter is represented as a string of ASCII digits
         indicating the time interval in seconds.  The default value of
         this parameter is infinity (i.e., the Begin command will never
         timeout).  The control flag for this parameter is -bt.

      Type of Service Advice

         The Type of Service Advice parameter contains information on
         the service characteristics the user desires from the offloaded
         protocol.  Included in this parameter is the precedence of the
         data transfer, and also indication of whether high throughput,
         fast response time, or low error rate is the primary goal.

         The format of this parameter is a letter immediately (i.e. no
         intervening spaces) followed by a digit.  The letter "T"
         indicates that high throughput is desired.  The letter "R"
         indicates minimal response time is the goal.  The letter "E"
         indicates that low error rates are the goal.  The letter "N"
         indicates there are no special service requirements to be
         conveyed.  The digit immediately following the character


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RFC 929                                                    December 1984
Proposed Host-Front End Protocol


         indicates the desired precedence level, with zero being the
         lowest, and nine being the highest.  The specific
         interpretation of this parameter is dependent on what service
         options are provided by the protocol.  The default value of
         this parameter is the lowest precedence (ROUTINE), and no
         special service requests.  The control flag for this parameter
         is -ts.

      Flow Control Advice

         The Flow Control Advice parameter contains information on the
         flow characteristics desired by the user.  Some applications
         such as file transfer operate more efficiently if the data is
         transferred in large pieces, while other, more interactive
         applications are more efficiently served if smaller pieces are
         used.  This parameter then indicates whether large or small
         data blocks should be used.  It is only relevant in stream or
         connection-oriented protocols, where the user sends more than a
         single piece of data.

         This parameter is represented by a single ASCII digit. A value
         0 means the data should be sent in relatively small blocks
         (e.g., character or line oriented applications), while a value
         9 means the data should be sent in relatively large blocks
         (e.g., block or file oriented applications). Other values
         represent sizes between those extremes.  The character "N"
         indicates that no special flow control advice is provided.  The
         actual interpretation of this parameter is dependent on the
         particular protocol in the OPE.  The default value of this
         parameter is no flow control advice. In this case, the protocol
         in the OPE will operate based only on information available in
         the OPE.  The control flag for this parameter is -fc.

      Local Address Primary Component

         This parameter contains the local address primary component. It
         is anticipated that under most circumstances, this component is
         known to both the Host and the OPE.  Consequently, this
         parameter is seldom required.  It would be useful if the Host
         desired to select one of several valid addresses, however.  The
         control flag for this parameter is -lp.

      Security

         The security parameters contain a set of security level,
         compartment, community of interest, and handling restriction
         information.  Currently, security is provided by performing all


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RFC 929                                                    December 1984
Proposed Host-Front End Protocol


         processing at system high level or at a single level.
         Consequently, these parameters are probably redundant, since
         the security information is known.  In the future, however,
         these parameters may be required.  Therefore a field is
         provided. The control flag for this parameter is -s.

      Protcol Idiosyncratic Parameters

         The remaining parameters are protocol idiosyncratic.  That is,
         each protocol that is off-loaded may have a set of these
         parameters, which are documented with a description of the
         off-loaded protocol.  The default value for these parameters is
         NULL, unless otherwise specified by a particular offloaded
         protocol.  The control flag for this set of parameters is -pi,
         which identifies the first protocol idiosyncratic parameters.
         Control flags for other protocol idiosyncratic parameters must
         be defined for each off-loaded protocol.

      Data

         After the Protocol Idiosyncratic Parameters, if any, and the
         required <nl>, if the protocol in play allows for it at this
         juncture the rest of the chunk will be interpreted as data to
         be transmitted.  That is, in connection oriented protocols data
         may or may not be permitted at connection initiation time, but
         in connectionless protocols it certainly makes sense to allow
         the H-FP Begin command to convey data. (This will also be
         useful when we get to the Condition command.)

      Responses

         The following responses have been identified for the Begin
         command:

            000    Command completed successfully
            101    Throughput not available; using maximum
            102    Reliability not available; using maximum
            103    Delay not available; using minimum
            110    Flow Control advice not followed; smaller blocks used
            111    Flow Control advice not followed; larger blocks used
            201    Failed; Begin not implemented in this direction
            202    Failed; timeout
            203    Failed; Begin command on already active channel
            300    Problem with multiple chunks
            301    Syntax problem with Begin command
            302    Protocol not supported in OPE/Host
            303    Active service not available


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RFC 929                                                    December 1984
Proposed Host-Front End Protocol


            304    Passive service not available
            305    Invalid Foreign Address Primary Component
            306    Invalid Transmit Discipline
            307    Invalid Foreign Address Secondary Component
            308    Invalid Local Address Secondary Component
            309    Invalid Timeout Interval
            310    Invalid Type of Service Advice
            311    Invalid Flow control Advice
            312    Invalid Local Address Primary Component
            401    Protocol Interpreter in OPE not responding
            402    Remote Protocol Interpreter not available
            403    Failed; insufficient protocol interpreter resources
            501    Failed; insufficient OPE resources
            601    Request violates security policy
            602    Security parameter problem

         Additionally, protocol idiosyncratic responses will be defined
         for each off-loaded protocol.

      Example of Begin Command

         The Begin command is the most complex of the H-FP Command
         Level. When the off-loaded protocol is TCP, the Begin command
         is used to open TCP connections.  One possible example of a
         Begin command issued by an inboard Telnet interpreter to open a
         TCP connection to ISIA, with no begin timeout interval, is:

            C BE TCP A ISIA 9 N 23 ,, ,, N0 S <nl>

         Where:

            TCP    The code for the protocol TCP
            A      Indicates Active Begin
            ISIA   The name of a Host at USC-ISI
            9      Mediation Level 9:  Full OPE mediation
            N      Non-blocking transmit
            23     Destination Telnet Port
            ,,     skip  over parameters  (Local Address Secondary,
                   Begin Timeout Interval)
            N0     Type of Service Advice:  No special Advice,
                   Normal Precedence
            S      Flow Control Advice: use small blocks

         This command will cause the OPE to invoke the TCP interpreter
         to generate the initial SYN packet to the well-known Telnet
         socket on Host ISIA.  It also informs the OPE to do all TCP
         related processing via the Mediation Level, accepts default


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RFC 929                                                    December 1984
Proposed Host-Front End Protocol


         Local Address parameters, and sets the Begin Timeout Interval
         to infinity.  The precedence of the TCP connection is Normal,