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A-CHAMPAIGN

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http://archive.org/details/networkunixsyste155holm

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ENGINEERING LIBRARY

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URBANA. ILLINOISy

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bySt eve Hd litgren

03/1S/75

CAC Document No. 155

Center for Advanced ComputationUniversity of Illinois at Urbana-Champaign

Urbana, Illinois 6l801

The Library of the

J UL 1 3 1976

University of Illinoisat Urbane- Champaign

Copyright 1975By the Board of Trustees of the

University of Illinois

IX 3/18/75

Count is the number of bytes to be transmittedbetween the file represented by 'filedes' and the byte arrayrepresented by 'buffer'. Mbytes is the number actuallytransmitted. For the read call/' 'nbytes* may be zero toindicate the end of file; in either case/- minus one will bereturned if there was an error.

For each open file* the system maintains a pointerto the next byte to be read or written. If n bytes aretransmitted/ the pointer advances n bytes. Data written to

a file affect only those oytes in the file which are indi-cated by the position of the write pointer and the count; noother part of the file is changed. If the system pointerindicates that any bytes being written would lie beyond theend of the file* the file is enlarged as needed.

Once the user has finished processing a file/- itshould be closed. This is affected with the following call:

close( f

i

ledes )

;

Although it is not absolutely necessary to do a

specific close on a file when finished/' '(the system closesall files when a program exits)/ it is a good practice*since the user is allowed only sixteen open files.

There are several additional system calls related toI/O which. wilt not be discussed in detail. A few of thefit ore notable ones allow the user to: get the status of a

file/, change the protection or ownership of a fite> create a

file* create a directory/' make a link to an existing file*and delete a file. For further information concerning thedifferent I/O calls the reader is directed to The UNIXProgrammer's Manual/ fifth edition* K. Thompson/ and D. M.Ritchie* June 1974.

The user communicates with the network via thesesame system calls. For example* if one wished to connect tothe the PDP-10 at Harvard* the following sequence of callsmight be used.

filedes = open( "/dev/net/harv" *2 );

if( filedes < )

printfC Harvard is dead");else

whileC (nbytes=read(f i ledes/buf *80)) > )

write ( 0*buf*nbytes );

The open instructs the system to open a Telnet connection toHarvard/ if minus one is returned/ the program prints a mes-sage and exits* otherwise the program will read any bytessent by Harvard and print them out on the controlling tele-type. This will go on until Harvard closes the connection(Read will return minus one when the connection is closed).

IX 3/18/75

UNIX Telnet

In order to communicate with remote hosts on the

ARPA network/ one first Logs in to UMIX as a normal user.The user then runs a program Telnet/ which after announcingitself leaves him with several options.

He may co

When Telnet sees a

quest as a paralcommand processor (

gar d I ess of whetheruser may simultaneoServer Telnet and c

When the T

its the host>en on the speccontrol is

er data recei v

character is

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accepan op

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an the user's typew

ntinue with his normal UNIX activities.UNIX command/ it will initiate the re-lel task/- in the same manner as the UNIXthe Shell). Since this may be done re-or not a network connection is open/ the

usly receive output from a foreign host'sonverse with the local UNIX system.

elnet-user opens a connection/ Telnetname and any special parameters/ and doesial file corresponding to that host,returned/ the connection is open. Anyed from the terminal not containing es-sent to the network file. Any data r e -

to a read on the network file/ is writtenri t er

.

Communication continues with the host until the userwishes to close the connection. The user simply makes thisknown to Telnet via a command/ and Telnet does a standardclose on the network file. The negotiation of closing thenetwork connection is left to the system/ freeing the userfor other computational work.

There is some character translation and invisiblecontrol information passed back and forth between theforeign host and the Telnet process. This involves recogni-tion of Telnet IACs and the translation of Carriage*eturn(CR) and Line Feed(LF) to Line Feed on all data re-eived from the network/ and the inverse translation of LF

to CR LF on all data sent to the network.

>ICP Structure

Due to the structure of both the IMP to HostC2D andlost to HostC33 network protocols/ data comes from the net-work destined not only for one of many active processes/ butfor the information of the local host as a whole. For exam-)le/ network traffic such as a Host to Host Reset/ whichgenerally signals that a foreign host has come "olive" must)e acknowledged to let that host know that the local hostitself is "alive". Therefore/ the local host must monitorlata coming from the net to perform not only a messageswitching function/ which is the bulk of network traffic/>ut to provide a control and status function.

Further/ when person associated with the local

IX 3/18/75

hostserveprovition

IIL5JeventtraffflowIt i

the s

NCP.

wishes to carry on a conversation with a networkr/ the Initial Connection ProtocolC] must be used tode a logical port at each site for succeeding informa-f low.

Experience with the ANTS Mark IC43 and ANTS Marksystems has shown that the above classes of network

s are relatively infrequent/- and that most networkic is in terms of user data flow and the associatedcontroK Host to Most Allocates and IMP to Host RFNMs).s also the case that the software required to implementtatus and control function is the bulkiest part of an

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Hardware and Software Requirements

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The base operating system occupies 24.5k words ofmemory. This system includes a large number of devicedrivers*- and enjoys a generous amount of space for I/Obuffers and system tables. A minimal system would require40k words of memory. It should be noted that UNIX alsorequires the memory management option offered by DEC to runat all.

The base operating system was developed by 3ellLaboratories in Murray Hill* New Jersey. The Bell installa-tion supports a high speed paper tape reader-punch/- nine-track magnetic tape/ and Dectape. 3esides the console

IX 3/18/75

terminal/- there are 14 variabte speed communication d a -

tasets/- and a 201 series dataset for spooling printout to a

communal line printer. There are also several one-of-a-kinddevices including a voice response unit/ a voice synthesiz-er/ a phototypesetter/ a digital switching networks and a

satellite PDP-11/20 which generates vectors/- curves/- and;haracters for a Tektronix 611 storage-tube display.

Pliability

As of this writing network UNIX has been running oni full time basis for about four weeks. During that period/;here were between three and four crashes a day. This is

lot a valid indicator because many of the failures were dueo hardware problems. More recently the hardware has beene-conf i gured to improve reliability and the crash rate hasieen reduced to one a day with a down time of 2-5 minutes.his is expected to continue/- but the sampling period hasnteen long enough for any dependable analysis.

vailability

Although the UNIX network software was developedithout ARPA supports the Center for Advanced Computation isilling to provide it gratis to trie people of the ARPA corn-

unity .

However/- Bell Laboratories must be contacted for a

icense to the base system itself. Bell's policy in theast has been to license the system to universities for a

Dminal fee/- $150.00/- and unfortunately for a cost of20/000.00 to "non-university" institutions.

In this light/ Bell was approached to see what theire action would be to an ARPA Network wide license. They saidhat they were open 'to suggestions. in that area. S o / shouldnough people desire a system/ perhaps a less expensiveicense fee can be negotiated.

In any case we are willing to help any group withcquisition of a system.

For further information concerning the system con-act

Steve HolagrenCenter for Advanced ComputationUniversity of Illinois-Urbana Illinois 61801

<217)-333~8469or

jft* 3/18/75

holngren at i si

Outlook and Future Plans

With the advent of Telnet in UMIX/ current plans areto run the system over the next one or two months and workout any remaining bugs. While this is going on/- extensiveDandwidth and load testing is going to take place and anyreasonable improvements made.

After Telnet has proved itself reliable/ the Opensystem call will be expanded to include further parameteri-zation. This parameterization will encompass connections tospecific sockets^ simplex connections based on a socketalready in use/ and the ability to listen on a local socket.

After those extensions/ net mail/ then network FTPand finally network RJE will be implemented. All will runas user programs so the size of the system kernel will noti ncrease .

Ultimately/ Server Telnet and Server FTP may beincorporated into the system/ but they are not a prioritypiece of work.

There is also interest in implementing some of theProcedure Call Protocol being developed by the NationalSoftware Works/ but no definite plans have been made.

Acknowledgements

•I am much indebted to Gary Grossman who participatedin the design and wrote the NCP Daemon; and to Steve Bunchwho was the the third member of our design group and wrotethe Kernel message software.

The three of us are particularly' appreciative of thecriticism and support of Dr. Hugh Folk/ Dr. Peter Alsberg/Greg Chesson/ John Mullen/ < a r I Kelley and Dave Healy.

References

1. Unix Time-Sharing SystemKen Thompson and Dennis RitchieCommunications of the ACMJuly 1974/ Vol 17/ Number 7

2. Specifications for the Interconnectionof a

Host to an IMPReport no. 1822 Bolt Beranek and Newman Inc

3/18/75

Chapter 3/ System Operation

3. Host/Host Protocol for the ARPA NetworkAlex Mckenzie*- 33NNIC Document 8246

A. Ants Mark I User's GuideKarl Kel leyCenter for Advanced Computation 2/1/74

Ants Mark Two SystemKarl KelleyCenter for Advanced Computation 1/10/74