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Over time digital techniques have been devel-

oped extensively and hence should replace older

techniques if it were possible to disregard exist-

ing assets. Digital transmission is now cheaper

and exhibits better quality than analog ones. But

several of the existing world-wide telenetworks

are still predominantly analog, represent large

assets and function well. Further expansion and

replacement – analog to digital – imply many

questions, trade-offs and techniques for change

or coexistence.

As the demand for communication channels be-

tween computers and their possibilities increase,

digital transmission and also packet switching

continue to become more advantageous. That is

especially the case for traffic consisting of many

and dynamically changing performance factors.

An example illustrates that:

Some computer co-operating applications are

characterized by burstyness. Machine A sends

one or more messages to machine B. Then for

some time nothing is sent because A has to do

something else, A’s user does some thinking, A

is awaiting answer or acknowledgement from B,

then B may suddenly respond with a large mes-

sage, and so on. Traffic in the communication

channel becomes bursty. Efficiency of such co-

operation often requires short transfer time to

avoid idle waiting of the receiver. This is typical

for answer- and acknowledge-type messages.

The length of various messages typically varies

a great deal. Transfer time for a message

depends on the bandwidth of the channel, i.e. the

bit transfer rate. Large bandwidth gets messages

through fast. This would tend to make relatively

poor use of the channel. It would be idling much

of the time. More bursty traffic means less effi-

cient use of the channel because of more idling

time. A packet switched channel may be used by

a multiplex of packet streams. It may be espe-

cially attractive to mix packet streams with dif-

ferent transfer time requirements. Urgent packets

slip through fast while packet streams of lower

transfer time requirement can wait and make use

of otherwise idle periods.

History of Initial Internet

Development

Development Teamwork

The Arpanet collaboration that eventually led

to the establishment of the Internet was carried

out by a handful of research groups collaborat-

ing intimately for many years. Lawrence “Larry”

Roberts initially led the Arpanet work as director

of ARPA’s Information Processing Techniques

Office – IPTO. Robert “Bob” Kahn later re-

placed him. More than anybody else Kahn was

the person who formulated goals and guided

development of the Internet-technology during

the most active development period. Vinton

“Vint” Cerf later assisted Kahn. Later on, Cerf

promoted and led the further development of the

technology and its applications. Vint Cerf today

appears as “Internet Guru number one”. All

these three persons distinguished themselves as

excellent professionals and were able to moder-

ate and lead the many capable and outspoken

researchers and research groups that took part

in the development.

During the 1970s the following ten groups par-

ticipated in the development of Internet technol-

ogy as one intimately collaborating team:

• Advanced Research Projects Agency – Infor-
  mation Processing Techniques Office, Wash-
  ington, DC – ARPA


• Bolt Beranek and Newman, Cambridge,
  Massachusetts – BBN


• Stanford Research International, Menlo Park,
  California – SRI


• University of California, Los Angeles – UCLA


• Information Sciences Institute, Marina del
  Rey, California – ISI


• Linkabit Corporation, San Diego, California
  
  
  • Linkabit
  
  
  
  


• Comsat Corporation, Gaithersburg, Maryland
  
  
  • Comsat
  
  
  
  


• Massachusetts Institute of Technology,
  Cambridge, Massachusetts – MIT


• University College London, England – UCL


• Norwegian Defence Research Establishment,
  Kjeller, Norway – NDRE.

Among these groups the company BBN had

many central and decisive roles in the develop-

ment. BBN was responsible for the daily opera-

Line x

Line y

Line y

A to B

B to A

Other traffic

in between

Packets

Dialog

In a packet switched network
each leg may carry a mixture
of traffic streams belonging
to several different “con-
versations”. Each packet is
addressed and has necessary
identification with it