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RFC 109 - Level III Server Protocol for the Lincoln Laboratory 3


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Network Working Group                                          J. Winett
Request for Comments: 109                         MIT Lincoln Laboratory
NIC: 5805                                                  24 March 1971

          Level III Server Protocol for the Lincoln Laboratory
                              360/67 Host

Disclaimer

   This material has not been reviewed for public release and is
   intended only for use with the ARPA network.  It should not be quoted
   or cited in any publication not related to the ARPA network.

Introduction

   The Lincoln Laboratory IBM 360/67 is connected to the ARPA network
   and acts as a serving host providing access to the CP-67 virtual
   machine operating system.  Upon completion of the Login procedure,
   users have control of a 360 virtual machine through a virtual 1052
   online console.  Attached to the virtual machine is a virtual card
   reader, card punch and line printer, and a number of disk storage
   devices.  The 360 virtual machine can be either a virtual 360/67 with
   dynamic address translation hardware or a standard System/360.  Most
   users run a standard 360 with 256K bytes of virtual memory and
   operate the CMS conversational monitor system.  CMS provides
   facilities for file creation, maintenance and manipulation, program
   development, debugging and execution, and a number of other useful
   utility functions.  The section in the Network Notebook on the
   Lincoln Laboratory 360/67 more fully describes the facilities
   available.

Network Control Program

   All communication with the 360/67 through the IMP are processed by a
   Network Control Program (NCP).  The NCP operates with the Host-Host
   Protocol described in the Network Working Group Document No. 1 dated
   3 August 1970.

Initial Connection Protocol

   To create a virtual machine from the network, a pair of connections
   must be made with the LOGGER.  The sockets to be used are assigned
   following the Initial Connection Protocol (ICP).  The LOGGER is
   enabled and waiting for an RTS control command for socket X'0A 0000
   01'.  This ICP socket corresponds to home X'0A', user X'0000', and
   tag X'01' (send gender).  Requests for connection on the ICP socket
   are stacked until it becomes free.  If the LOGGER is willing to

   service another network user, a 32 bit socket ID of a receive socket
   will be sent over this initial connection and the ICP socket will
   then be closed.  If the LOGGER is not willing to service another
   network user, it will not complete the initial connection for the ICP
   socket and will refuse the request by closing the connection without
   completing it.

LOGGER Protocol

   Once a pair of user sockets have been assigned, the connection
   protocol should be completed on these sockets.  The LOGGER then
   expects to receive (on the receive socket) one 8-bit byte indicating
   the data type which characterizes the transmission code used to
   communicate with the network user over this pair of sockets.  A code
   of X'01' implies 7 bit ASCII code in 8-bit bytes with the leading bit
   zero.  A code of X'02' implies 8-bit EBCDIC code.  When the data type
   code is received, the LOGGER will echo back the data type code over
   the send socket followed by the message:

            LINCOLN LABORATORY CP-67 ONLINE NL

   in the appropriate code.  (In ASCII, NL is transmitted as CR LF).

   The procedure continues according to the normal CP-67 login protocol
   with the LOGGER performing an additional function of mapping network
   userids and passwords into valid CP-67 userids and passwords.  This
   mapping is specified by entries in a file (the LOGGER FILE) which the
   LOGGER accesses.  If a network userid does not match an entry in the
   file or if the password given does not match the corresponding
   network password, the usual CP responses will be sent to the users.
   Thus network access to the Lincoln Laboratory system is restricted to
   those accounts for which an appropriate entry has been made in the
   LOGGER FILE.

   It should be noted that CP transmits a BYP code (Bypass) to suspend
   the printing of characters keyed while a password is being entered.
   After the password has been entered, CP transmits a RES code
   (Restore) to resume the printing when characters are keyed.  When
   communicating in ASCII, these character codes are converted to X'FF'
   since no corresponding ASCII code is defined.  Refer to the Network
   Resource Notebook for more details on CP-67 and on CMS.

The NET Account

   Lincoln Laboratory is providing one account which can be used by
   network users to familiarize themselves with our time-sharing system.
   The userid of this account is NET and the password is ARPA.  This
   account has 900 records of storage, which can store approximately

   720,000 characters.  NET users are free to ERASE any file on this
   account since many different people may use this account.

The SERVER Protocol

   CP-67 operates on a line at a time, i.e., a group of characters are
   processed as a line and not as a sequence of individual characters.
   Also, the system does normally buffer input lines, that is, input is
   not normally entered until requested by a read from the system.  With
   IBM 2741 or 1052 terminals, the keyboard is locked until a read is
   requested.  The virtual terminals through which network users have
   access to the CP-67 system have been designed to support either a
   line oriented terminal or a character oriented terminal.  When CP
   requests a line of input, the SERVER transmits a prompting code
   X'80'.  This character can be used to signal a user process to change
   transmission modes and to transmit an input line.  Characters
   received by the SERVER are buffered until a NL character is received.
   Lines received can then be used to satisfy CP requests for an input
   line.

   CP may send out lines which may or may not end with a NL character.
   If a line does not end with a NL character, the prompting character
   will naturally be sent following the output line to request input to
   a CP process.

   When a user wishes to interrupt a CP process, i.e., to change modes,
   an interrupt code X'80' should be sent to the SERVER.  This code will
   result in an asynchronous interrupt being sent to the running
   process, stimulating the pressing of the 'attention' button on a 2741
   terminal.  Together with the transmission of the interrupt code, the
   user should cause an INS to be sent over the send link.  This signal
   will be synchronized with the interrupt code.  If the interrupt code
   has not yet been received and processed, all characters buffered and
   those received before the receipt of the interrupt code will be
   flushed, i.e., deleted.  When the interrupt code is received, it will
   be paired with the previously received INS.  If an INS is received
   after an interrupt code has been received and processed, the INS will
   be paired with this previously received interrupt code.

   If CP has a line to send to a user after it has requested an input
   line but before it has received any input, the SERVER will transmit
   an INS on the user's receive link to notify the user that previously
   sent prompting character should be retracted and that a line has been
   or will be sent to the user.  This message line is called a
   "warning".

Graphic and Control Codes

   Figure 1 gives the 8-bit codes for the EBCDIC graphics and controls.
   Figure 2 gives the 7-bit codes for the ASCII graphics and controls.
   The controls are tabulated and compared in Figure 3.  The standard
   interpretation of the ASCII controls are given in Figure 4.

   There are 4 ASCII codes which do not have a corresponding graphic or
   control in the EBCDIC code.  The EBCDIC codes given to these codes
   are as follows:

                   |     Hex Code
             ASCII |-------+--------
            Symbol | ASCII | EBCDIC
            -------+-------+--------
               DC3 |  13   |  3A
                   |       |
                `  |  60   |  70
                   |       |
                \  |  5C   |  71
                   |       |
                ^  |  5E   |  72

   There are 29 EBCDIC graphics codes and 19 EBCDIC control codes which
   do not have a corresponding graphic or control in the ASCII code.  In
   addition, there are 84 other EBCDIC codes whose interpretation is
   unspecified.  Four of these codes have been chosen to correspond to
   the ASCII control and ASCII graphics which do not have a
   corresponding EBCDIC code.  When converting EBCDIC codes to ASCII
   codes, the remaining 80 codes plus the 29 EBCDIC graphics and 18
   EBCDIC controls (not counting NL) are converted into the code X'FF'.
   The NL character is treated specially.  The NL character, EBCDIC code
   X'15', is converted into the two character sequence CR LF, i.e.,
   ASCII X'0D 0A'.  As stated above, the code X'80' is transmitted as a
   prompting character whenever CP requests an input line.

   On converting from ASCII to EBCDIC, if any code other than the 128
   ASCII codes, or the interrupt codem X'80', is received, it is
   converted to the code X'FF'.  In addition , whenever the two ASCII
   characters CR LF are found sequentially in the input stream, they are
   converted into the single EBCDIC character NL.

   [In Figure 1, positions shown as "[?]" cannot be printed in ASCII.]

        0 0  0   0   0   0   0   0   0   1   1   1   1   1   1   1   1
        1 0  0   0   0   1   1   1   1   0   0   0   0   1   1   1   1
        2 0  0   1   1   0   0   1   1   0   0   1   1   0   0   1   1
        3 0  1   0   1   0   1   0   1   0   1   0   1   0   1   0   1
   4567+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0000|NUL|DLE|DS |   |SP | & | - |   |   |   |[?]|[?]|   |   |   | 0 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0001|SOH|DC1|SOS|   |   |   | / |   | a | j |[?]|[?]| A | J |   | 1 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0010|STX|DC2|FS |SYN|   |   |   |   | b | k | s |[?]| B | K | S | 2 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0011|ETX|TM |   |   |   |   |   |   | c | l | t |[?]| C | L | T | 3 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0100|PF |RES|BYP|PN |   |   |   |   | d | m | u |[?]| D | M | U | 4 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0101|HT |NL |LF |RS |   |   |   |   | e | n | v |[?]| E | N | V | 5 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0110|LC |BS |ETB|UC |   |   |   |   | f | o | w |[?]| F | O | W | 6 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0111|DEL|IL |ESC|EOT|   |   |   |   | g | p | x |[?]| G | P | X | 7 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   1000|   |CAN|   |   |   |   |   |   | h | q | y |[?]| H | Q | Y | 8 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   1001|   |EM |   |   |   |   |   |   | i | r | z |[?]| I | R | Z | 9 |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   1010|SMM|CC |SM |   |[1]| ! |   | : |   |   |   |   |   |   |   |   |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   1011|VT |CU1|CU2|CU3| . | $ | , | # | { | } |[?]|[?]|   |   |   |   |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   1100|FF |IFS|   |DC4| < | * | % | @ |[?]|[?]|[?]|[?]|   |   |   |   |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   1101|CR |IGS|ENQ|NAK| ( | ) | _ | ' |[?]|[?]| [ | ] |   |   |   |   |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   1110|SO |IRS|ACK|   | + | ; | > | = |[?]|[?]|[?]|[?]|   |   |   |   |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   1111|SI |IUS|BEL|SUB| | |[2]| ? | " |[?]|[?]|[?]|[?]|   |   |   |   |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

                         +---+---+---+---+---+---+---+---+
                         | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
                         +---+---+---+---+---+---+---+---+
                                   Code Structure

                                      Figure 1.

            Extended Binary-Coded Decimal Interchange Code (EBCDIC)

            8 0   0   0   0   0   0   0   0
            7 0   0   0   0   1   1   1   1
            6 0   0   1   1   0   0   1   1
            5 0   1   0   1   0   1   0   1
        4321+---+---+---+---+---+---+---+---+
        0000|NUL|DLE|SP | 0 | @ | P | ` | p |
            +---+---+---+---+---+---+---+---+
        0001|SOH|DC1| ! | 1 | A | Q | a | q |
            +---+---+---+---+---+---+---+---+
        0010|STX|DC2| " | 2 | B | R | b | r |
            +---+---+---+---+---+---+---+---+
        0011|ETX|DC3| # | 3 | C | S | c | s |
            +---+---+---+---+---+---+---+---+
        0100|EOT|DC4| $ | 4 | D | T | d | t |
            +---+---+---+---+---+---+---+---+
        0101|ENQ|NAK| % | 5 | E | U | e | u |
            +---+---+---+---+---+---+---+---+
        0110|ACK|SYN| & | 6 | F | V | f | v |
            +---+---+---+---+---+---+---+---+
        0111|BEL|ETB| ' | 7 | G | W | g | w |
            +---+---+---+---+---+---+---+---+
        1000|BS |CAN| ( | 8 | H | X | h | x |
            +---+---+---+---+---+---+---+---+
        1001|HT |EM | ) | 9 | I | Y | i | y |
            +---+---+---+---+---+---+---+---+
        1010|LF |SUB| * | : | J | Z | j | z |
            +---+---+---+---+---+---+---+---+
        1011|VT |ESC| + | ; | K | [ | k | { |
            +---+---+---+---+---+---+---+---+
        1100|FF |FS | , | < | L | \ | l | | |
            +---+---+---+---+---+---+---+---+
        1101|CR |GS | - | = | M | ] | m | } |
            +---+---+---+---+---+---+---+---+
        1110|SO |RS | . | > | N | ^ | n | ~ |
            +---+---+---+---+---+---+---+---+
        1111|SI |SU | / | ? | O | _ | o |DEL|
            +---+---+---+---+---+---+---+---+
    +---+---+---+---+---+---+---+---+---+---+---+---+
            | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
            +---+---+---+---+---+---+---+---+
                     Code Structure

                        Figure 2.

   USA Standard Code for Information Interchange (USASCII)

   CAT     EBCDIC  ASCII   TTY     PTTC    FUNCTION

           NUL     NUL     NULL            Null
   CC      SOH     SOH     SOM             Start of Heading
   CC      STX     STX     EOA     EOA (D) Start of Text
   CC      ETX     ETX     EOM             End of Text
   DC      PF                      PF      Punch Off
   FE      HT      HT      H.TAB   TAB     Horizontal Tab
   GR      LC                      LC      Lower Case
           DEL     DEL     RUBOUT  DEL     Delete
           SMM                             Start of Manual Message
   FE      VT      VT      V.TAB           Vertical Tab
   FE      FF      FF      FORM            Form Feed
   FE      CR      CR      RETURN          Carriage Return
   GR      SO      SO      SO              Shift Out
   GR      SI      SI      SI              Shift In
   CC      DLE     DLE     DC0             Data Link Escape
   DC      DC1     DC1     X-ON            Device Control 1
   DC      DC2     DC2     TAPE ON         Device Control 2
           TM                              Tape Mark
   DC      RES                     RES     Restore
   FE      NL                      NL      New Line
   FE      BS      BS              BS      Backspace
           IL                      IL      Idle
           CAN     CAN     FE0     CAN     Cancel
           EM      EM      S1              End of Medium
           CC                              Cursor Control
   CU      CU1                             Customer Use 1
   IS      IFS     FS      S4              Info. Field Separator
   IS      IGS     GS      S5              Info. Group Separator
   IS      IRS     RS      S6              Info. Record Separator
   IS      IUS     US      S7              Info Unit Separator
   ED      DS                              Digit Select
   ED      SOS                             Start of Significance
   ED      FS                              Field Separator
   DC      BYP                     BYP     Bypass
   FE      LF      LF      LF      LF      Line Feed
   CC      ETB     ETB     LEM     EOB (B) End of Text Block
           ESC     ESC     S3      PRE     Escape
           SM                              Set Mode
   CU      CU2                             Customer Use 2
   CC      ENQ     ENQ     WRU             Enquiry
   CC      ACK     ACK     RU      (Y)     Acknowledge
           BEL     BEL     BELL            Bell
   CC      SYN     SYN     SYNC            Synchronous Idle
   DC      PN                      PN      Punch On
   DC      RS                      RS      Reader Stop
   GR      UC                      UC      Upper Case

   CC      EOT     EOT     EOT     EOT (C) End of Transmission
   CU      CU3                             Customer Use 3
   DC      DC4     DC4     TAPE OFF        Device Control 4
   CC      NAK     NAK     ERROR   (N)     Negative Acknowledge
           SUB     SUB     S2              Substitute
   DC              DC3     X-OFF           Device Control 3

                       Figure 3

                Control Functions Compared

   CC   (Communication Control).  A functional character intended to
         control or facilitate transmission of information over
         communication networks.

   FE   (Format Effector).  A functional character which controls the
         layout or positioning of information in printing or display
         devices.

   IS   (Information Separator).  A character which is used to separate
         and qualify information in a logical sense.  There is a group
         of four such characters, which are to be used in a hierarchical
         order.

   DC   (Device Control).  A functional character used for the control
         of ancillary devices associated with data processing of
         telecommunication systems, more especially switching devices
         "on" and "off".

   ED   (Edit and Mark).  A control character used by the System/360
         Edit and Mark (EDMK) instruction for the formatting of
         alphanumeric fields.

   GB   (Graphic Control).  A control character indicating that the code
         combinations which follow are to be interpreted in a particular
         code table, depending upon the particular control character.

   CU   (Customer Use).  A character excluded from future assignment by
         IBM.  These "protected" codes are intended for use by customer
         systems so that their use will not conflict with a possible
         future IBM use.

                           Figure 3 (Continued)

                     Categories of Control Functions

   NUL  (Null).  The all-zeros character which may serve to accomplish
         time fill and media fill.

   SOH  (Start of Heading).  A communication control character used at
         the beginning of a sequence of characters which constitute a
         machine-sensible address or routing information.  Such a
         sequence is referred to as the _heading_.  An STX character has
         the effect of terminating a heading.

   STX  (Start of Text).  A communication control character which
         precedes a sequence of characters that is to be treated as an
         entity and transmitted through to the ultimate destination.
         Such a sequence is referred to as _text_.  SIX may be used to
         terminate a sequence of characters started by SOH.

   ETX  (End of Text).  A communication control character used to
         terminate a sequence of characters started with STX and
         transmitted as an entity.

   EOT  (End of Transmission).  A communication control character used
         to indicate the conclusion of a transmission, which may have
         contained one or more texts and any associated headings.

   ENQ  (Enquiry).  A communication control character used in data
         communication systems as a request for a response from a remote
         station.  It may be used as a "Who Are You" (WRU) to obtain
         identification, or may be used to obtain station status, or
         both.

   ACK  (Acknowledge).  A communication control character transmitted by
         a receiver as an affirmative response to a sender.

   BEL  (Bell).  A character for use when these is a need to call for
         human attention.  It may control alarm or attention devices.

   BS   (Backspace).  A format effector which controls the movement of
         the printing position one printing space backward on the same
         printing line (applicable also to display devices).

   HT   (Horizontal Tabulation).  A format effector which controls the
         movement of the printing position to the next in a series of
         predetermined positions along the printing line (applicable
         also to display devices and the skip function on punched
         cards.)

   LF   (Line Feed).  A format effector which controls the movement of
         the printing position to the next printing line (also
         applicable to display devices).

   VT   (Vertical Tabulation).  A format effector which controls the
         movement of the printing position to the next in a series of
         predetermined printing lines (also applicable to display
         devices).

   FF   (Form Feed).  A format effector which controls the movement of
         the printing position to the first predetermined printing line
         on the next form or page (also applicable to display devices).

   CR   (Carriage Return).  A format effector which controls the
         movement of the printing position to the first printing
         position on the same printing line (also applicable to display
         devices).

   SO    (Shift Out).  A control character indicating that the code
         combinations which follow shall be interpreted as outside of
         the character set of the standard code table until a Shift In
         Character is reached.

   SI    (Shift In).  A control character indicating that the code
         combinations which follow shall be interpreted according to the
         standard code table.

   DLE   (Data Link Escape).  A communication control character which
         will change the meaning of a limited number of contiguously
         following characters.  It is used exclusively to provide
         supplementary controls in data communication networks.

   DC1, DC2, DC3, DC4 (Device Controls).  Characters for the control of
         ancillary devices associated with data processing or
         telecommunication systems, more especially switching devices
         "on" and "off".  (If a single "stop" control is required to
         interrupt of turn off ancillary devices, DC4 is the preferred
         assignment.)

   NAK  (Negative Acknowledge).  A communication control character
         transmitted by a receiver as a negative response to a sender.

   SYN   (Synchronous Idle).  A communication control character used by
         a synchronous transmission system in the absence of any other
         character to provide a signal from which synchronism may be
         achieved or retained.

   ETB  (End of Transmission Block).  A communication control character
         used to indicate the end of a block of data for communication
         purposes.  ETB is used for blocking data where the block
         structure is not necessarily related to the processing format.

   CAN  (Cancel).  A control character used to indicate that the data
         with which it is sent is in error or is to be disregarded.

   EM   (End of Medium).  A control character associated with the sent
         data which may be used to identify the physical end of the
         medium, or the end of the used, or wanted, portion of
         information recorded on a medium.  (The position of this
         character does not necessarily correspond to the physical end
         of the medium.

   SS   (Start of Special Sequence).  A control character used to
         indicate the start of a variable length sequence of characters
         which have special significance or which are to have special
         handling.

   ESC  (Escape).  A control character intended to provide code
         extension (supplementary characters) in general information
         interchange.  The Escape character itself is a prefix affecting
         the interpretation of a limited number of contiguously
         following characters.

   FS   (File Separator), GS (Group Separator), RS (Record Separator)
         and US (Unit Separator).  These information separators may be
         used within data in optional fashion, except that the
         hierarchical relationship shall be : FS is the must inclusive,
         then GS, then RS, and US is least inclusive.  (The content and
         length of a File, Group, Record, or Unit are not specified.)

   DEL  (Delete).  This character is used primarily to "erase" or
         "obliterate" erroneous or unwanted characters in perforated
         tape.  (In the strict sense, DEL is not a control character.)

                               Figure 4

                        ASCII Control Functions

Endnotes

   [1] - Cent sign
   [2] - Logical not ("bent bar")
   [?] - Graphics not in ASCII.  See Postscript or PDF version of
         this document.

          [This RFC was put into machine readable form for entry]
          [into the online RFC archives by Lorrie Shiota, 10/02]

 

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