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rfc:rfc88

Network Working Group R. Braden Request for Comments: 88 S. Wolfe NIC: 5668 UCLA/CCN

                                                       13 January 1971
        NETRJS - A THIRD LEVEL PROTOCOL FOR REMOTE JOB ENTRY
 A.  Introduction
 NETRJS is the name for a message protocol and set of control
 conventions which will allow users at remote Hosts to access the RJS
 ("Remote Job Service") remote batch subsystem of CCN.  RJS[1] was
 written at CCN to support remote batch (car reader/line printer)
 terminals over communications lines.
 RJS makes a remote batch terminal's unit record devices operate as if
 they were at the central site; thus, a remote user enters OS/360
 jobs, complete with JCL, into the remote reader.  The jobs are
 spooled into the operating system and run in their turn, and the
 printed and/or punched output is returned to the remote terminal from
 which the jobs originated (unless the user or operator re-routes the
 output).  The remote terminal may also include a console typewriter
 to be used by the remote operator to receive and send messages and to
 exert control over his terminal [2].
 When RJS is used via the ARPA Network, the "remote terminal" is
 expected to be a multiprogrammed user process in a remote Host.  We
 will use the RJS term "remote site" for such a user process, which
 presumably simulates unit record devices by file I/O.  Furthermore,
 several users at the same remote Host may simultaneously use NETRJS,
 acting as independent "remote sites" distinguished by 8-character
 names called _terminal-ids_ (because each remote site appears to RJS
 as a separate physical terminal).  Valid terminal-ids will be
 assigned to individual users or user groups at remote Hosts who wish
 to use NETRJS.
 Under NETRJS, a separate ARPA network connection is opened from this
 remote site to CCN for each (simulated) unit record device.  Each
 such connection will be called a _channel_ and be designated _input_
 or _output_ with reference to CCN.  We define a _standard_ remote
 site in NETRJS to have the following five channels (See Figure 1):
    1._Operator Input Channel_ - Commands and messages entered by
       remote "operator" console.
    2 _Operator Output Channel_ - Message stream which would normally
       be directed to remote operator.

Braden, et. al. [Page 1] RFC 88 NETRJS - A THIRD LEVEL PROTOCOL 13 January 1971

    3._Input Stream_ - One simulated Hollerith card reader for job
       submission.
    4._Printer Stream_ - One simulated line printer to record printed
       output (system messages and SYSOUT data sets) from jobs.
    5._Punch Stream_ - One simulated card punch, capable of recording
       arbitrary (i.e., transparent) binary text.
 RJS actually will support more than one reader, printer, and punch at
 each remote terminal, so the NETRJS protocol could easily be expanded
 to allow multiple simultaneous I/O streams to each Network user.
 However, this does not presently appear useful, as the ARPA Network
 bandwidth will normally be the limitation on the transmission speed
 under NETRJS.
 Under NETRJS, the text of a single network message is called a
 _block_.  A block is of variable length, up to 900 bytes (except
 operator input and output blocks, which may not exceed 130 bytes).
 Here the term _byte_ refers to the set of 8 bits representing one
 character; each byte is to be aligned on an 8-bit boundary within the
 message (and block).  Thus we may consider a block to be a string of
 bytes.  The detailed format of a block will be defined in Sections E,
 F, and G, using essentially the formalism suggested by Bobrow and
 Sutherland in RFC #31.
 Since the central site Host (CCN) is an IBM 360, NETRJS uses the IBM
 EBCDIC character code to avoid redundant code conversion at both
 hosts in those cases when the remote host also uses EBCDIC
 internally.  However, the message formats make no assumption about
 the code, and in fact, "object decks" sent to the (simulated) card
 punch will normally contain arbitrary binary text.
 To maximize the use of the available Network bandwidth, we strongly
 recommend transmitting input blocks as large as possible; CCN will
 always fully block NETRJS output.  Furthermore, to avoid excessive
 overhead, we urge that all NETRJS users make their marking _a
 multiple of 8 bits_, so the messages received at CCN arrive on a byte
 boundary.
 B.  Starting a Session[3]
 The initial connection protocol for NETRJS is essentially that of
 Crocker in RFC #66 (as restated by Harslem and Heafner in RFC #80),
 with some extensions.  User U at a remote Host presumably requests
 his outgoing logger to make a NETRJS connection to CCN.  This

Braden, et. al. [Page 2] RFC 88 NETRJS - A THIRD LEVEL PROTOCOL 13 January 1971

 logger does so by first sending an initial RFC to connect socket
 (user,aen) = (U,s) to CCN socket (0,5).  User 0 at CCN is the
 incoming logger, and aen = 5 signifies NETRJS.
 The CCN incoming logger will allocate a set of (six) consecutive aen
 numbers A, A+1,......A+5, for user U, return a message containing the
 socket number (U,A) as specified in RFC #66, and close the initial
 connection.  The remote and central sites will then open an input
 channel between CCN socket (U,A) (socket f in Figure 1) and remote
 socket (U, s+1).  This is the remote operator input channel.  The
 other devices have fixed aen's at CCN assigned relative to A, in
 particular:
                               CCN Socket
       Channel                 (User,aen)
       Operator Input          (U,A)
       Operator Output         (U,A+1)
       Card Reader (No. 1)     (U,A+2)
       Printer (No. 1)         (U,A+3)
       Punch (No. 1)           (U,A+5)
 Once the operator input channel is open, the remote site must
 transmit a valid RJS signon message [2].  This message is free-format
 and consists of the command verb "SIGNON" followed by the user's
 terminal-id.  If RJS does not recognize the terminal-id or has no
 available Line Handler for the Network, it will indicate refusal by
 closing the operator input channel.  Central site issues subsequent
 RFC's for the other channels listed above only in response to
 corresponding RFC's from the remote site
 To terminate the session, the remote site may close the console input
 channel (socket "a" in figure 1).  Alternatively, the user can enter
 a SIGNOFF command through the operator input channel; in this case,
 RJS will wait until the current job output streams are complete and
 then terminate the session.  RJS terminates the session by closing
 the console output channel (socket g).  Also, if RJS should abend
 then socket g will close.  If either site terminates the session, all
 other connections for this remote site should be closed.  Note that a
 user can submit a number of jobs, sign off, and later receive his
 output when he signs on again.

C. Channel Control

 Flow control in NETRJS is handled by the Network protocol ALL
 mechanism.  Before transmission of a stream of records can begin on a
 particular channel, the remote site must issue an RFC and Central
 must reply.  This allows the central site to determine the remote

Braden, et. al. [Page 3] RFC 88 NETRJS - A THIRD LEVEL PROTOCOL 13 January 1971

 configuration dynamically.  A particular card reader, printer, or
 punch channel is open only while it is active, so the receiver need
 not tie up buffer space needlessly.  Each of these channels, when
 open, assumes a buffer allocation of at least 900 bytes at the
 receiver.
 The operator input and output channels, on the other hand, are open
 throughout the session.  On these channels the receiver must provide
 an allocation of at least 130 bytes.
 After sending the SIGNON command over the operator input channel, the
 remote site should send RFC's for all output channels which are ready
 to receive data.  When output is available for that site, Central
 returns an RFC and begins transmission.  Central closes an output
 channel (socket i and j) at the end of the output for each complete
 batch job.[4]  The remote site must then send a new RFC and Central
 must reply with an RFC to start output for another job to that
 device.  This gives the remote site a chance to allocate a new file
 for each job without breaking the output within a job.  If the user
 at the remote site wants to cancel (or backspace or defer) the output
 of a particular job, he enters appropriate RJS commands[2] on the
 operator input channel.
 When the remote site is ready to submit a job (or stack of
 consecutive jobs), it issues an RFC for the card reader input
 channel.  The remote site is not required to close the channel
 (socket c) after each job in a "stack" of jobs, but he must close it
 following the last job in the stack to initiate its processing.
 It may be necessary for the receiver site to abort a particular
 channel, perhaps due to a transmission error (see Section D below on
 checking) or a disk I/O error.  The receiver may abort a channel
 (other than console output) by closing it (sockets d, e, f, and h).
 This action signals the transmitter to re-transmit the information
 after the channel has been reopened (initiated by the remote site, as
 always).  The transmitter, on the other hand, aborts a channel by
 sending a block with a particular bit combination (e = 2 in BCBYTE;
 see Section E).
 If either site aborts card reader (input) channel, RJS will discard
 the text of the last partially-spooled job; the remote site should
 re-transmit this job.  Note that repeating an entire stack will enter
 duplicate jobs into the system, but the second copy of a job will
 "flush" due to its duplicate job name.
 If a printer or punch (output) channel is aborted, Central will re-
 transmit from the beginning of the current SYSOUT data set; the
 effect is the same as a RESTART command.[2]

Braden, et. al. [Page 4] RFC 88 NETRJS - A THIRD LEVEL PROTOCOL 13 January 1971

 If the operator input channel is aborted, the remote site must re-
 transmit the last _block_.  Finally, the operator output channel has
 no abort condition defined.  Central will never send Channel Abort
 message on this channel; if the remote site closes its socket (socket
 b), Central will not re-transmit, but simply cease sending messages
 until the channel is reopened.  Therefore a remote site can operate
 without an operator output channel; however we do not recommend this,
 as the user will then miss operator advisory messages such as a
 warning of an impending IPL.

D. Checking

 The nature of remote job entry service is such that a low rate of
 undetected errors is mandatory.  The IMP's use CRC's and sequence
 numbers over the communication lines, so the effective IMP-IMP error
 rate should be negligible.  Although there is no checking provided
 for the IMP-Host interface, it seems likely that these interfaces
 will either be reliable or fail catastrophically; it seems unlikely
 that "drop-outs" or other random failures will occur.  Therefore only
 the following simple checks are provided:
 1. Each block will (at least initially) contain a fixed bit check
    pattern using both on and off states of each bit path in the 16
    bit PDA interface at CCN.
    It is anticipated that even this crude check on IMP-Host
    transmission will be useful both during the initial checkout of
    hardware and software and also later if the interface becomes
    marginal.  However, either site can omit the check pattern if it
    sets a bit in the Block Control Byte (BCBYTE); see Section F.
 2. Each block contains a sequence number.  Again this is intended for
    initial checkout and to signal catastrophic hardware or software
    problems.  If the receiver detects an incorrect check pattern or
    block sequence number, he aborts the channel by closing the
    corresponding network connection; the remote site should then
    issue an RFC to re-establish the network connection.  The sequence
    number of the first block after an RFC is 0.  The  numbers are
    never reset while the connection is open.

Braden, et. al. [Page 5] RFC 88 NETRJS - A THIRD LEVEL PROTOCOL 13 January 1971

E. Block Format

    BLOCK <---- BLOCKHEAD + (RECORD = r) + ENDOFBLOCK
                Here r > 0
                       =
 BLOCKHEAD <--  BCBYTE + [e=0=>CHECK] + DEVBYTE
                The Blockhead field consists of a Block Control Byte,
                a 32-bit check field CHECK, and a Device Byte.
 BCBYTE <----   '1'BIT + e:ERRORCONTROL + b:BLKSEQ
                Here BLKSEQ contains a 5-bit modulo 32 block sequence
                number b.  ERRORCONTROL is a 2 bit field with the
                following meanings:
                e=0 :  Normal block.  Contains a (presumably valid)
                       check field CHECK.
                e=1 :  Block contains no check field CHECK.
                e=2 :  Abort channel, initiated by transmitter.
                       Channels is not closed, transmission restarts
                       on job-related boundary.
 DEVBYTE <----  '1'BIT + n:DEVNO + t:DEVTYPE
                This byte identifies a particular remote device, i.e.,
                it identifies a stream.  DEVTYPE specifies the type of
                device, as follows:
                t=1:  Output to remote operator console.
                  2:  Input from remote operator console.
                  3:  Input from card reader.
                  4:  Output to printer.
                  5:  Output to card punch.
                6,7:  Unused.
                DEVNO is a 3-bit integer which identifies the
                particular device type of type t at this remote site.
 CHECK <---     '10101111'BYTE + 01010000'BYTE + '11111010'BYTE +
                                                 '00000101'BYTE
 ENDOFBLOCK<----'0'BYTE

Braden, et. al. [Page 6] RFC 88 NETRJS - A THIRD LEVEL PROTOCOL 13 January 1971

Record Format

    RECORD <------ DATA RECORD | JOBNAMERECORD
 The first record sent on a printer or punch output channel will be a
 JOBNAMERECORD, identifying the OS/360 jobname of the job which
 produced the following output.
 DATARECORD <---   '10'BIT2 + DEVCNTRL + (STRING=p) + ENDOFRECORD
 JOBNAMERECORD <-- '11000000'BYTE + '11001000'BYTE + JOBNAME +
                   ENDOFRECORD
 JOBNAME <----     (TEXTBYTE = 8)
                   This is the 8-character OS/360 jobname for the
                   following job.
 DEVCNTRL <-----    d:BIT2 + k:BIT4
                   DEVCNTRL specifies carriage control for a printer,
                   so if the device is not a printer then DEVCNTRL
                   should be '000000'.  For a printer:
                   d=0     : Space k lines after printing; 0 < k < 3
                                                             =   =
                             is allowed
                   d=2     : Immediately space k lines.
                   d=1, k=1: Skip to top of new page after printing.
                   d=3, k=1: Immediately skip to top of new page.
 STRING <---         ('100' + i:DUPCOUNT)| This is a string of i
                   consecutive blanks.
                   ('101' + i:DUPCOUNT + TEXTBYTE)|
                   This is a string of i consecutive duplicates of
                   TEXTBYTE.
                   ('11' + j:LENGTH + (TEXTBYTE=j)| This is an
                   uncompressed string of j characters.
 ENDOFRECORD <----   '0'BYTE

Braden, et. al. [Page 7] RFC 88 NETRJS - A THIRD LEVEL PROTOCOL 13 January 1971

G. Field Definitions

 Name*           Meaning                 Length (bits)
 _____           _______                 _____________
 BIT             1-bit field                  1
 BIT2            2-bit field                  2
 BIT4            4-bit field                  4
 BLKSEQ          Block sequence number        5
 BYTE            8-bit field aligned on 8-bit 8
                 boundary
 CHECK           Block check number          32
 DEVNO           Device number of a given     3
                 type
 DEVTYPE         Device type                  4
 DUPCOUNT        Number of replications of    5
                 duplicated character in
                 compressed text.
 ERRORCONTROL    Block transmission error     2
                 control.
 LENGTH          Length in bytes of the       6
                 following string of text.
 TEXTBYTE        An 8-bit byte of text        8
  • Note: All non-terminal fields whose names end in

"…BYTE" represent bytes in both length and

         alignment.

Braden, et. al. [Page 8] RFC 88 NETRJS - A THIRD LEVEL PROTOCOL 13 January 1971

 H.  NOTES AND REFERENCES
 1. Martin, V.A. and Springer, T.W., "Implementation of A Remote Job
    Service", Technical Report TR2, Campus Computing Network, UCLA,
    Los Angeles, (undated).
 2. The RJS operator commands and messages are described in detail in
    Reference 1.
 3. We use the phrase "starting a session" rather than "logging on"
    because RJS has its own log on procedure, which is, we suppose, a
    fourth-level protocol.
 4. Note that NETRJS uses closing of connections as end-of-file
    signals.
         REMOTE SITE             CENTRAL SITE (CCN)
    +---------------------+    +--------------------+
    |                 a   |    |                    |
    | Console Input  o----------->o f               |
    |                 b   |    |                    |
    | Console Output o<-----------o g               |
    |                 c   |    |                    |
    | Card Reader    o------------o h               |
    |                 d   |    |                    |
    | Printer        o<-----------o i               |
    |                 e   |    |                    |
    | Card Punch     o<-----------o j               |
    |                     |    |                    |
    +---------------------+    +--------------------+
                         FIGURE 1
              ARPA Network Connections (Channels)
            For a Standard Remote Site Under NETRJS
    R.T. Braden/rb.
    S.M. Wolfe
         [This RFC was put into machine readable form for entry]
          [into the online RFC archives by Lorrie Shiota, 10/01]

Braden, et. al. [Page 9]

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