NWG/RFC# 681                                  JBP 14-MAY-75 14:38  32157
3/18/75     NETWORK UNIX                                     S. Holmgren



                            NETWORK UNIX                               1

                         RFC 681 NIC 32157                             2

INTRODUCTION                                                           3

   THE  UNIX  TIME-SHARING  SYSTEM  [1] PRESENTS SEVERAL INTERESTING
   CAPABILITIES AS AN ARPA NETWORK MINI-HOST.   IT  OFFERS POWERFUL
   LOCAL  PROCESSING FACILITIES IN TERMS OF USER PROGRAMS, SEVERAL
   COMPILERS, AN EDITOR BASED ON QED, A  VERSATILE  DOCUMENT
   PREPARATION  SYSTEM,  AND  AN EFFICIENT FILE SYSTEM FEATURING
   SOPHISTICATED ACCESS CONTROL, MOUNTABLE AND DE-MOUNTABLE
   VOLUMES, AND A UNIFIED TREATMENT OF PERIPHERALS AS SPECIAL FILES.  3a

   THE NETWORK CONTROL PROGRAM (NCP), IS  INTEGRATED  WITHIN THE
   UNIX FILE SYSTEM.  NETWORK CONNECTIONS ARE TREATED AS SPECIAL
   FILES WHICH CAN BE ACCESSED THROUGH STANDARD UNIX I/O CALLS; VIZ.
   READ,  WRITE,  OPEN, CLOSE.  SPECIAL FILES HAVE DIRECTORY ENTRIES
   SIMILAR TO NORMAL FILES EXCEPT THAT CERTAIN FLAG  BITS  ARE  SET.
   THESE FLAG BITS CAUSE SYSTEM I/O ROUTINES TO TAKE SPECIAL ACTION.
   IN UNIX, SPECIAL FILES SIGNIFY PERIPHERAL DEVICES.  FOR  EXAMPLE,
   I/O  TRANSACTION  WITH  MAGTAPE ZERO WOULD BE ACCOMPLISHED BY
   ACCESSING THE SPECIAL FILE, "/DEV/MT0".  FOR THE UNIX NETWORK
   SYSTEM,  ADDITIONAL  SPECIAL FILES WERE CREATED EACH OF WHICH
   SPECIFIES A HOST ON THE  ARPA  NETWORK.  FOR  EXAMPLE
   "/DEV/NET/HARV" REPRESENTS  THE PDP-10 AT HARVARD.  THIS SIMPLE
   ACCESS MECHANISM, THROUGH THE FILING SYSTEM, ALLOWS STANDARD ARPA
   PROTOCOLS SUCH AS TELNET  AND  FTP  TO  BE  IMPLEMENTED AS
   SWAPPABLE USER PROGRAMS, RESIDENT ONLY WHEN NEEDED.  FURTHERMORE,
   A USER MAY WRITE HIS OWN PROGRAMS TO COMMUNICATE WITH THESE
   SPECIAL FILES JUST AS THE TELNET PROGRAM DOES.  THE SAMPLE
   PROGRAM  FOUND BELOW  DEPICTS  THE ESSENTIALS OF NETWORKING FROM
   UNIX.                                                              3b

STANDARD I/O                                                           4

   TO  PRESENT  THE  BASIC PROPERTIES OF UNIX I/O, THE READ, WRITE,
   OPEN, AND CLOSE FUNCTION CALLS ARE SUMMARIZED BELOW.  EACH CALL
   MAY RESULT IN AN ERROR CODE OF MINUS ONE.                          4a

   TO MANIPULATE AN EXISTING FILE WITH READS OR  WRITES,  IT MUST
   FIRST BE OPENED WITH THE FOLLOWING CALL:                           4b
NWG/RFC# 681                                  JBP 14-MAY-75 14:38  32157
3/18/75     NETWORK UNIX                                     S. Holmgren



      FILEDES = OPEN( "ANYFILENAME",FLAG )                           4b1

   WHERE  "ANYFILENAME" IS THE ARBITRARY NAME OF THE FILE TO BE
   OPENED.  THE SECOND PARAMETER INDICATES WHETHER THE FILE IS TO BE
   READ,  WRITTEN, OR UPDATED.  THE RETURNED VALUE "FILEDES", IS
   CALLED A FILE DESCRIPTOR. IT IS AN INTEGER USED TO  IDENTIFY  THE
   FILE IN SUBSEQUENT CALLS TO READ AND WRITE.                        4c

   ONCE A FILE HAS BEEN OPENED, THE FOLLOWING CALLS  MAY  BE USED:    4d

      NBYTES = READ( FILEDES,BUFFER,COUNT );
      NBYTES = WRITE( FILEDES,BUFFER,COUNT );                        4d1

   COUNT IS THE NUMBER OF BYTES TO  BE  TRANSMITTED  BETWEEN THE
   FILE REPRESENTED BY 'FILEDES' AND THE BYTE ARRAY REPRESENTED BY
   'BUFFER'.  NBYTES IS THE NUMBER ACTUALLY TRANSMITTED.  FOR THE
   READ  CALL,  'NBYTES' MAY BE ZERO TO INDICATE THE END OF FILE; IN
   EITHER CASE, MINUS ONE WILL BE RETURNED IF THERE WAS AN ERROR.     4e

   FOR EACH OPEN FILE, THE SYSTEM MAINTAINS A POINTER TO THE NEXT
   BYTE TO BE READ OR WRITTEN.  IF N BYTES ARE TRANSMITTED, THE
   POINTER  ADVANCES  N  BYTES.   DATA WRITTEN TO A FILE AFFECT ONLY
   THOSE BYTES IN THE FILE WHICH ARE INDICATED BY  THE  POSITION  OF
   THE  WRITE  POINTER  AND  THE COUNT; NO OTHER PART OF THE FILE IS
   CHANGED.  IF THE SYSTEM POINTER INDICATES THAT  ANY  BYTES  BEING
   WRITTEN  WOULD  LIE  BEYOND  THE END OF THE FILE, THE FILE IS
   ENLARGED AS NEEDED.                                                4f

   ONCE  THE  USER HAS FINISHED PROCESSING A FILE, IT SHOULD BE
   CLOSED.  THIS IS AFFECTED WITH THE FOLLOWING CALL:                 4g

      CLOSE( FILEDES );                                              4g1

   ALTHOUGH IT IS NOT ABSOLUTELY NECESSARY TO DO A  SPECIFIC CLOSE
   ON A FILE WHEN FINISHED, (THE SYSTEM CLOSES ALL FILES WHEN A
   PROGRAM EXITS), IT IS A GOOD PRACTICE, SINCE THE  USER  IS
   ALLOWED ONLY SIXTEEN OPEN FILES.                                   4h

   THERE ARE SEVERAL ADDITIONAL SYSTEM CALLS RELATED TO  I/O WHICH
   WILL NOT BE DISCUSSED IN DETAIL.  A FEW OF THE MORE NOTABLE ONES
   ALLOW THE USER TO: GET THE STATUS OF A FILE, CHANGE THE
   PROTECTION  OR OWNERSHIP OF A FILE, CREATE A FILE, CREATE A
   DIRECTORY, MAKE A LINK TO AN EXISTING FILE,  AND  DELETE  A

NWG/RFC# 681                                  JBP 14-MAY-75 14:38  32157
3/18/75     NETWORK UNIX                                     S. Holmgren



   FILE.   FOR FURTHER INFORMATION CONCERNING THE DIFFERENT I/O
   CALLS THE READER IS DIRECTED TO THE UNIX PROGRAMMER'S MANUAL,
   FIFTH  EDITION,  K. THOMPSON, AND D. M. RITCHIE, JUNE 1974.        4i

   THE USER COMMUNICATES WITH THE  NETWORK  VIA  THESE  SAME SYSTEM
   CALLS.   FOR EXAMPLE, IF ONE WISHED TO CONNECT TO THE THE PDP-10
   AT HARVARD, THE FOLLOWING SEQUENCE OF CALLS MIGHT BE USED.         4j

      FILEDES = OPEN( "/DEV/NET/HARV",2 );
      IF( FILEDES < 0 )
         PRINTF(" HARVARD IS DEAD");
      ELSE
         WHILE( (NBYTES=READ(FILEDES,BUF,80)) > 0 )
            WRITE( 0,BUF,NBYTES );                                   4j1

   THE OPEN INSTRUCTS THE SYSTEM TO OPEN A TELNET CONNECTION TO
   HARVARD, IF MINUS ONE IS RETURNED, THE PROGRAM PRINTS A MESSAGE
   AND EXITS,  OTHERWISE THE PROGRAM WILL READ ANY BYTES SENT BY
   HARVARD AND PRINT THEM OUT ON THE CONTROLLING TELETYPE. THIS WILL
   GO  ON UNTIL  HARVARD  CLOSES THE CONNECTION (READ WILL RETURN
   MINUS ONE WHEN THE CONNECTION IS CLOSED).                          4k

UNIX TELNET                                                            5

   IN ORDER TO COMMUNICATE WITH REMOTE  HOSTS  ON  THE  ARPA
   NETWORK,  ONE  FIRST  LOGS IN TO UNIX AS A NORMAL USER.  THE USER
   THEN RUNS A PROGRAM, TELNET, WHICH AFTER ANNOUNCING ITSELF LEAVES
   HIM WITH SEVERAL OPTIONS.                                          5a

   HE MAY CONTINUE WITH HIS  NORMAL  UNIX  ACTIVITIES.  WHEN TELNET
   SEES  A  UNIX  COMMAND, IT WILL INITIATE THE REQUEST AS A
   PARALLEL TASK, IN THE SAME MANNER AS THE UNIX  COMMAND  PROCESSOR
   (THE SHELL).  SINCE THIS MAY BE DONE REGARDLESS OF WHETHER OR NOT
   A NETWORK CONNECTION IS OPEN, THE USER MAY SIMULTANEOUSLY RECEIVE
   OUTPUT  FROM A FOREIGN HOST'S SERVER TELNET AND CONVERSE WITH THE
   LOCAL UNIX SYSTEM.                                                 5b

   WHEN  THE  TELNET-USER OPENS A CONNECTION, TELNET ACCEPTS THE
   HOST NAME AND ANY SPECIAL PARAMETERS, AND DOES AN OPEN ON THE
   SPECIAL  FILE  CORRESPONDING  TO  THAT HOST.  WHEN CONTROL IS
   RETURNED, THE CONNECTION IS OPEN.   ANY FURTHER DATA RECEIVED
   FROM THE  TERMINAL NOT CONTAINING ESCAPE CHARACTER IS SENT TO THE






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NWG/RFC# 681                                  JBP 14-MAY-75 14:38  32157
3/18/75     NETWORK UNIX                                     S. Holmgren



   NETWORK FILE.   ANY DATA RECEIVED IN RESPONSE TO A READ ON THE
   NETWORK FILE, IS WRITTEN ON THE USER'S TYPEWRITER.                 5c

   COMMUNICATION CONTINUES WITH  THE  HOST  UNTIL  THE  USER WISHES
   TO CLOSE THE CONNECTION.  THE USER SIMPLY MAKES THIS KNOWN TO
   TELNET VIA A COMMAND, AND TELNET DOES A STANDARD CLOSE ON  THE
   NETWORK  FILE.  THE NEGOTIATION OF CLOSING THE NETWORK CONNECTION
   IS LEFT TO THE SYSTEM, FREEING THE USER FOR  OTHER  COMPUTATIONAL
   WORK.                                                              5d

   THERE IS SOME CHARACTER TRANSLATION AND INVISIBLE CONTROL
   INFORMATION  PASSED  BACK  AND FORTH BETWEEN THE FOREIGN HOST AND
   THE TELNET PROCESS. THIS INVOLVES RECOGNITION OF TELNET IACS  AND
   THE  TRANSLATION OF CARRIAGE RETURN(CR) AND LINE FEED(LF) TO LINE
   FEED ON ALL DATA RECEIVED  FROM  THE  NETWORK,  AND  THE  INVERSE
   TRANSLATION OF LF TO CR LF ON ALL DATA SENT TO THE NETWORK.        5e

NCP STRUCTURE                                                          6

   DUE  TO THE STRUCTURE OF BOTH THE IMP TO HOST[2] AND HOST TO
   HOST[3] NETWORK PROTOCOLS, DATA COMES FROM  THE  NETWORK
   DESTINED  NOT  ONLY  FOR  ONE  OF MANY ACTIVE PROCESSES, BUT FOR
   THE INFORMATION OF THE LOCAL HOST AS A WHOLE.  FOR  EXAMPLE,
   NETWORK TRAFFIC  SUCH  AS  A  HOST TO HOST RESET, WHICH GENERALLY
   SIGNALS THAT A FOREIGN HOST HAS COME "ALIVE" MUST BE ACKNOWLEDGED
   TO  LET THAT HOST KNOW THAT THE LOCAL HOST ITSELF IS "ALIVE".
   THEREFORE, THE LOCAL HOST MUST MONITOR DATA COMING FROM THE NET
   TO  PERFORM NOT  ONLY A MESSAGE SWITCHING FUNCTION, WHICH IS THE
   BULK OF NETWORK TRAFFIC, BUT TO PROVIDE A CONTROL AND STATUS
   FUNCTION.                                                          6a

   FURTHER,  WHEN  A  PERSON  ASSOCIATED WITH THE LOCAL HOST WISHES
   TO CARRY ON A CONVERSATION WITH A NETWORK SERVER, THE INITIAL
   CONNECTION  PROTOCOL[4]  MUST  BE USED TO PROVIDE A LOGICAL PORT
   AT EACH SITE FOR SUCCEEDING INFORMATION FLOW.                      6b

   EXPERIENCE  WITH  THE  ANTS MARK I[5] AND ANTS MARK II[6] SYSTEMS
   HAS SHOWN THAT THE ABOVE CLASSES OF  NETWORK  EVENTS  ARE
   RELATIVELY  INFREQUENT, AND THAT MOST NETWORK TRAFFIC IS IN TERMS
   OF USER DATA FLOW AND THE ASSOCIATED FLOW CONTROL( HOST  TO  HOST
   ALLOCATES  AND  IMP TO HOST RFNMS).  IT IS ALSO THE CASE THAT THE
   SOFTWARE REQUIRED TO IMPLEMENT THE STATUS AND CONTROL FUNCTION IS
   THE BULKIEST PART OF AN NCP.                                       6c





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NWG/RFC# 681                                  JBP 14-MAY-75 14:38  32157
3/18/75     NETWORK UNIX                                     S. Holmgren



   IN UNIX, THE KERNEL OF  THE  OPERATING  SYSTEM  IS  CORERESIDENT
   AND  NON-SWAPPABLE.   A LARGE KERNEL REDUCES THE MEMORY AVAILABLE
   FOR USER PROGRAMS.  THUS IT IS  DESIRABLE  TO  MINIMIZE THE
   AMOUNT  OF  CODE ADDED TO THE BASIC UNIX KERNEL FOR THE NCP. FOR
   THIS REASON, THE NCP IS IMPLEMENTED IN TWO PARTS. ONE PART IS
   ROOTED  IN  THE  KERNEL  AND  MAKES UP THE NON-SWAPPABLE SECTION,
   ABOUT 3.5K WORDS OF CORE.  THE OTHER SECTION (CALLED THE NCP
   DAEMON)  DEALS  WITH USER REQUESTS TO OPEN AND CLOSE CONNECTIONS
   AND HANDLES THE STATUS TRAFFIC DESCRIBED ABOVE.  THE NCP DAEMON
   RUNS AS A SWAPPABLE USER PROCESS OF ABOUT 8.5K WORDS IN SIZE, AND
   COMMUNICATES WITH THE KERNEL VIA A SPECIAL FILE.                   6d

HARDWARE AND SOFTWARE REQUIREMENTS                                     7

   THE  NETWORK  SOFTWARE  FOR  UNIX  WAS  DEVELOPED  ON   A
   PDP-11/50,  WITH MEMORY MANAGEMENT, TWO RK05 DISK PACKS, TWO NINE
   TRACK MAGTAPE DRIVES, FOUR DECTAPE DRIVES, 32K WORDS OF CORE, AND
   THREE TERMINALS.  PRESENTLY THIS HAS BEEN EXPANDED TO ENCOMPASS A
   DH11 TERMINAL MULTIPLEXOR, AN  RP03  MOVING  HEAD  DISK,  A  TWIN
   PLATTER  RF11  FIXED  HEAD DISK, FLOATING POINT, AND 48K OF CORE.
   USER FILES ARE STORED ON THE RP03. THE RF11 IS  USED  AS  A  SWAP
   DISK  AND  FOR  TEMPORARY FILE STORAGE; ONE RK05 PLATTER CONTAINS
   THE SYSTEM FILES, AND THE SECOND CONTAINS  LOGIN  AND  ACCOUNTING
   INFORMATION.   IN THE NEAR FUTURE, THE SYSTEM WILL BE EXPANDED TO
   128K WORDS OF CORE MEMORY WITH 10 DIAL IN AND 10 HARD WIRED
   TERMINAL LINES.                                                    7a

   THE BASE OPERATING SYSTEM OCCUPIES 24.5K WORDS OF MEMORY. THIS
   SYSTEM INCLUDES A LARGE NUMBER OF DEVICE DRIVERS, AND ENJOYS A
   GENEROUS AMOUNT OF SPACE FOR I/O BUFFERS AND SYSTEM TABLES.   A
   MINIMAL  SYSTEM  WOULD  REQUIRE 40K WORDS OF HARDWARE MEMORY.  IT
   SHOULD BE NOTED THAT UNIX ALSO  REQUIRES  THE  MEMORY  MANAGEMENT
   OPTION OFFERED BY DEC TO RUN AT ALL.                               7b

   THE BASE OPERATING SYSTEM WAS DEVELOPED BY  BELL  LABORATORIES
   IN  MURRAY  HILL, NEW JERSEY.  THE BELL INSTALLATION SUPPORTS A
   HIGH SPEED PAPER TAPE READER-PUNCH,  NINE-TRACK  MAGNETIC TAPE,
   AND  DECTAPE.  BESIDES  THE CONSOLE TERMINAL, THERE ARE 14
   VARIABLE SPEED COMMUNICATION DATASETS, AND A 201  SERIES  DATASET
   FOR SPOOLING PRINTOUT TO A COMMUNAL LINE PRINTER.  THERE ARE ALSO
   SEVERAL ONE-OF-A-KIND DEVICES INCLUDING A VOICE RESPONSE UNIT,  A
   VOICE  SYNTHESIZER,  A  PHOTOTYPESETTER, A DIGITAL SWITCHING






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NWG/RFC# 681                                  JBP 14-MAY-75 14:38  32157
3/18/75     NETWORK UNIX                                     S. Holmgren



   NETWORK, AND A SATELLITE PDP-11/20 WHICH GENERATES VECTORS,
   CURVES, AND CHARACTERS FOR A TEKTRONIX 611 STORAGE-TUBE DISPLAY.   7c

RELIABILITY                                                            8

   AS  OF  THIS  WRITING, NETWORK UNIX HAS BEEN RUNNING ON A FULL
   TIME BASIS FOR ABOUT FOUR WEEKS.  DURING THAT PERIOD,  THERE WERE
   BETWEEN  THREE AND FOUR CRASHES A DAY.  THIS IS NOT A VALID
   INDICATOR BECAUSE MANY OF THE FAILURES WERE DUE TO HARDWARE
   COMPLICATIONS.  MORE RECENTLY THE HARDWARE HAS BEEN RE-CONFIGURED
   TO IMPROVE RELIABILITY AND THE CRASH RATE HAS BEEN REDUCED TO ONE
   A DAY  WITH A DOWN TIME OF 2-3 MINS.  THIS IS EXPECTED TO
   CONTINUE, BUT THE SAMPLING PERIOD HASNT BEEN LONG ENOUGH FOR ANY
   DEPENDABLE ANALYSIS.                                               8a

AVAILABILITY                                                           9

   ALTHOUGH  THE UNIX NETWORK SOFTWARE WAS DEVELOPED WITHOUT ARPA
   SUPPORT, THE CENTER FOR ADVANCED COMPUTATION IS  WILLING  TO
   PROVIDE IT GRATIS TO THE PEOPLE OF THE ARPA COMMUNITY.             9a

   HOWEVER BELL LABORATORIES MUST BE CONTACTED  FOR  A  LISCENSE  TO
   THE BASE SYSTEM ITSELF.  BELL'S POLICY IN THE PAST HAS BEEN TO
   LISCENSE THE SYSTEM TO UNIVERSITIES FOR  A  NOMINAL  FEE,
   $150.00,  AND  UNFORTUNATELY  FOR  A  COST OF $20,000.00 TO
   "NONUNIVERSITY" INSTITUTIONS.                                      9b

   IN THIS LIGHT BELL WAS APPROACHED TO SEE WHAT THEIR REACTION
   WOULD BE TO AN ARPA NETWORK WIDE LISCENSE,  THEY  SAID  THEY WERE
   OPEN  TO SUGGESTIONS IN THAT AREA.  SO SHOULD ENOUGH PEOPLE
   BECOME INTERESTED, PERHAPS A LESS EXPENSIVE FEE CAN BE
   NEGOTIATED.                                                        9c

   INTERESTED USERS  WHO  HAVE  EITHER  SOURCE  LISTINGS  OR SOURCE
   FILES INCLUDE:                                                     9d

   THE RAND CORPORATION WHICH IS USING OUR IMPLEMENTATION AS A BASIS
   FOR THEIR OWN VERSION.                                             9e

   LINCOLN LABORATORIES WHICH HAS A  SOURCE  LISTING  TO  BE USED AS
   AN AID IN EVALUATION OF THE UNIX SYSTEM.                           9f







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NWG/RFC# 681                                  JBP 14-MAY-75 14:38  32157
3/18/75     NETWORK UNIX                                     S. Holmgren



   THE INCO CORPORATION OF MC LEAN VIR.  HAS  A  LISTING  TO HELP IN
   THE INSTALLATION OF AN NCP INTO DEC'S RSTS OPERATING SYSTEM.       9g

   IN  ANY  CASE  WE  ARE WILLING TO HELP ANY GROUP WITH ACQUISITION
   OF A SYSTEM.                                                       9h

      FOR FURTHER INFORMATION CONCERNING THE SYSTEM CONTACT:         9h1

         STEVE HOLMGREN
         210 ADVANCED COMPUTATION BLDG.
         UNIVERSITY OF ILLINOIS
         URBANA ILLINOIS 61801

            (217)-333-8469
            OR
            HOLMGREN AT BBN

OUTLOOK AND FUTURE PLANS                                              10

   WITH  THE  ADVENT OF TELNET IN UNIX, CURRENT PLANS ARE TO RUN THE
   SYSTEM OVER THE NEXT ONE OR TWO MONTHS AND WORK  OUT  ANY
   REMAINING  BUGS.  WHILE  THIS IS GOING ON, EXTENSIVE BANDWITH AND
   LOAD  TESTING  IS  GOING  TO  TAKE  PLACE  AND   ANY   REASONABLE
   IMPROVEMENTS MADE.                                                10a

   AFTER TELNET HAS PROVED ITSELF RELIABLE, THE OPEN  SYSTEM CALL
   WILL BE EXPANDED TO INCLUDE FURTHER PARAMETERIZATION.  THIS
   PARAMETERIZATION WILL ENCOMPASS CONNECTIONS TO SPECIFIC  SOCKETS,
   SIMPLEX  CONNECTIONS  BASED  ON  A SOCKET ALREADY IN USE, AND THE
   ABILITY TO LISTEN ON A LOCAL SOCKET.                              10b

   AFTER  THOSE  EXTENSIONS,  NET MAIL, THEN NETWORK FTP AND FINALLY
   NETWORK RJE WILL BE IMPLEMENTED.  ALL WILL  RUN  AS  USER
   PROGRAMS SO THE KERNEL SYSTEM SIZE WILL NOT INCREASE.             10c

   THERE IS ALSO INTEREST IN IMPLEMENTING SOME OF  THE  PROCEDURE
   CALL  PROTOCOL  BEING  DEVELOPED BY THE NATIONAL SOFTWARE WORKS,
   BUT NO DEFINATE PLAN HAVE BEEN MADE.                              10d

ACKNOWLEDGEMENTS                                                      11

   I AM MUCH INDEBTED TO GARY GROSSMAN WHO  PARTICIPATED  IN THE
   DESIGN  AND WROTE THE NCP DAEMON; AND TO STEVE BUNCH WHO WAS THE





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NWG/RFC# 681                                  JBP 14-MAY-75 14:38  32157
3/18/75     NETWORK UNIX                                     S. Holmgren



   THE THIRD MEMBER OF OUR DESIGN GROUP  AND  WROTE  THE  KERNEL
   MESSAGE SOFTWARE.                                                 11a

   THE THREE OF US ARE PARTICULARLY APPRECIATIVE OF THE CRITICISM
   AND  SUPPORT  OF  DR.  HUGH FOLK, DR. PETER ALSBERG, GREG
   CHESSON, JOHN MULLEN, KARL KELLEY AND DAVE HEALY.                 11b

REFERENCES                                                            12

   1.  UNIX TIME-SHARING SYSTEM
   KEN THOMPSON AND DENNIS RITCHIE
   COMMUNICATIONS OF THE ACM
   JULY 1974, VOL 17, NUMBER 7                                       12a

   2.  SPECIFICATIONS FOR THE INTERCONNECTION OF A
   HOST TO AN IMP
   REPORT NO. 1822 BOLT BERANEK AND NEWMAN INC.
   CHAPTER 3, SYSTEM OPERATION                                       12b

   3.  HOST/HOST PROTOCOL FOR THE ARPA NETWORK
   ALEX MCKENZIE, BBN
   NIC DOCUMENT 8246                                                 12c

   4.  OFFICIAL INITIAL CONNECIION PROTOCOL
   DOCUMENT #2
   J. POSTEL,  UCLA-NMC
   NIC DOCUMENT 7101                                                 12d

   5.  ANTS MARK I USER'S GUIDE
   KARL KELLEY
   CENTER FOR ADVANCED COMPUTATION  2/1/74                           12e

   6.  ANTS MARK TWO SYSTEM
   KARL KELLEY
   CENTER FOR ADVANCED COMPUTATION  1/10/74                          12f













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