rfc48.txt

<VC++网络游戏建摸与实现>源代码

        C = ok      The Init was legal and the socket FS is being
                    contacted.  When the connection is established or
                    when FS refuses, the process will receive an event.

        C = busy    The local socket was in use by a port on this or
                    some other process with the same user number.  No
                    action was taken.

        C = homosex The AEN and FS were either both send or both receive
                    sockets.

        C = nohost  The host designated within FS isn't known.

        C = bufbig  Bsiz is too large.

   Listen (P,AEN,Bsize;C)

        P     Specifies a port of the process.
        AEN   Specifies a local socket.
        Bsiz  Specified a buffer size.
        C     The returned legality code.

   Codes for C are

        C = ok
        C = busy
        C = bufbig

   The local socket specifies by AEN is attached to P.  If there is a
   waiting call, it is processed; otherwise no action is taken.  When a
   call comes in, a connection will be established and the process
   notified via an event.

   Close (P)

        P Specifies a port of the process.

   Any activity is stopped, and the port becomes free for other use.

   Transmit (P,M,L1;L2,C)

        P     Specifies port with an open connection.
        M     The text to be transmitted.
        L1    Specifies the length of the text.
        L2    The length actually transmitted.
        C     The error code.





Postel & Crocker                                               [Page 13]

RFC 48                A Possible Protocol Plateau             April 1970


   Transmission between the processes on either side of the port takes
   place.

   Codes for C are

        C = ok
   or
        C = not open     if no connection is currently open and
                         otherwise uninhibited
   Status (P;C)

   The status of port P is returned as C.

IV. The NCP

   We view the NCP as having five component programs, three associative
   tables, some queues and buffers, and a link assignment table.  Each
   site will of course, vary this design to meet its needs, so our
   design is only illustrative.

   The Component Programs

      1. The Input Handler

         This is an interrupt driven input routine.  It initiates Imp-
         to-Host transmission into a resident buffer and wakes up the
         Input Interpreter when transmission is complete.

      2. The Output Handler

         This is an interrupt driven output routine.  It initiates
         Host-to-Imp transmission out of a resident buffer and wakes up
         the Output Scheduler when transmission is complete.

      3. The Input Interpreter

         This program decides whether the input is a regular message
         intended for a user, a control message, an Imp-to-Host message,
         or an error.  For each class of message, this program takes the
         appropriate action.

      4. The Output Scheduler

         Three classes of message are sent to the Imp

            (a) Host-to-Imp messages
            (b) Control messages
            (c) Regular messages



Postel & Crocker                                               [Page 14]

RFC 48                A Possible Protocol Plateau             April 1970


         We believe that a priority should be imposed among these
         classes.  The priority we suggest is the ordering above. The
         Output Scheduler selects the highest priority message and
         gives it to the Output Handler.

      5. The System Call Interpreter

         This program interprets requests from the user.

   The two interesting components are the Input Interpreter and the
   System Call Interpreter.  These are similar in that the Input
   Interpreter services foreign requests and the System Call Interpreter
   services local requests.

   Associative Tables

   We envision that the bulk of the NCP's data base is in three
   associative tables.  By "associative", we mean that there is some
   lookup routine which is presented with a key and either returns
   successfully with a pointer to the corresponding entry, or fails if
   no entry corresponds to the key.

      1. The Rendezvous Table

         "Requests-for-connection" and other attributes of a
         connection are held in this table.  This table is accessed by
         local socket, but other tables have pointers to existing
         entries.

            The components of an entry are:

            (a) local socket   (key)
            (b) foreign socket
            (c) link
            (d) queue of callers
            (e) text queue
            (f) connection state
            (g) flow state
            (h) pointer to attached port

            An entry is created when a user executes either an Init or a
            Listen system call or when a <RFC> is received.  Some fields
            are unused until the connection is established, e.g. the
            foreign socket is not known until a <RFC> arrives if the
            user did a Listen.






Postel & Crocker                                               [Page 15]

RFC 48                A Possible Protocol Plateau             April 1970


      2. The Input Link Table

            The Input Interpreter uses the foreign host and link as a
            key to get a pointer to the entry in the rendezvous table
            for the connection using the incoming link.

      3. The Output Link Table

            In order to interpret RFNM's, the Input Interpreter needs a
            table in the same form as the Input Link Table but using
            outgoing links.

   Link Assignment Table

   This is a very simple structure which keeps track of which links are
   in use for each host.  One word per host probably suffices.

   The following diagram is our conception of the Network Control
   Program.  Boxes represent tables and Buffers, boxes with angled
   corners and a double bottom represent Queues, and jagged boxes
   represent component programs, the arrows represent data paths.

   The abbreviated names have the following meanings.

   ILT   - Input Link Table

   OLT   - Output Link Table

   LAT   - Link Assignment Table

   RT    - Rendezvous Table

   HIQ   - Host to Imp Queue

   OCCQ  - Output Control Command Queue

   ORMQ  - Output Regular Message Queue

   IHBuf - Buffer filled by the Input Handler from the IMP and
           emptied by the Input Interpreter

   OHBuf - Buffer of outgoing messages filled from the Queues
           by the Output Scheduler and emptied by the Output
           Handler.







Postel & Crocker                                               [Page 16]

RFC 48                A Possible Protocol Plateau             April 1970


                              +---------+
                              |  I M P  |
                              +---------+
                                v     ^
                                |     |
    +---------------------------|-----|------------------------------+
    |                           |     |                              |
    |   /\/\/\/\/\/\/\          |     |     /\/\/\/\/\/\/\           |
    |   \            / <--------+     +---< \            /           |
    |   /  Input     \                      /  Output    \           |
    |   \   Handler  /                      \   Handler  / <----+    |
    |   /            \ >------+             /            \      |    |
    |   \/\/\/\/\/\/\/        |             \/\/\/\/\/\/\/      ^    |
    |                         v                              +-----+ |
    |                      +-----+                           | OH  | |
    |                      | IM  |                           | Buf | |
    |                      | Buf |                           +-----+ |
    |                      +-----+          /\/\/\/\/\/\/\/\    ^    |
    | /\/\/\/\/\/\/\/\        v      +----> \              /    |    |
    | \              /        |      |      /  Output      \ >--+    |
    | /              \ <------+      ^      \              /         |
    | \  Input       /           /-----\    /   Scheduler  \         |
    | /              \ >-------->| HIQ |    \              /         |
    | \  Interpreter /           |_____|    /              \         |
    | /              \ >----+    \_____/    \/\/\/\/\/\/\/\/         |
    | \/\/\/\/\/\/\/\/      |                ^     v    ^            |
    |   ^   ^    ^   \      |    /-----\     |     |    |    /-----\ |
    |   |    \    \   \     |    |  O  |     |     |    |    |  O  | |
    |   |     \    \   \    +--->|  C  |>----+     |    +---<|  R  | |
    |   v     v     v   \        |  C  |           |         |  M  | |
    | +---+ +---+ +---+  \       |  Q  |           v         |  Q  | |
    | |   | |   | |   |   \      |_____|      +---------+    |_____| |
    | |ILT| |LAT| |OLT|    \     \_____/      |         |    \_____/ |
    | |   | |   | |   |     \       ^         |   R T   |       ^    |
    | +---+ +---+ +---+      +------|-------->|         |       |    |
    |         v                     |         +---------+       |    |
    |         |                     ^              ^            |    |
    |         |            /\/\/\/\/\/\/\/\        |            |    |
    |         |            \              /        |            |    |
    |         +----------->/    System    \<-------+            |    |
    |                      \     Call     /                     |    |
    |                      /  Interpreter \>--------------------+    |
    |                      \              /                          |
    |                  +-->/              \>--+                      |
    |                  |   \/\/\/\/\/\/\/\/   |                      |
    +------------------|----------------------|----------------------+
                       |                      |
                       +---< system calls <---+



Postel & Crocker                                               [Page 17]

RFC 48                A Possible Protocol Plateau             April 1970


       [ This RFC was put into machine readable form for entry ]
   [ into the online RFC archives by Donald and Jill Eastlake 1999 ]

[Editor's note: The original hand-drawn diagram represented
Queues by cylinders and component programs by "squishy ameoba
like things".]













































Postel & Crocker                                               [Page 18]