The Internet is, of course, a global packet switched data network and the early history of its development centres mainly on the evolotion of packet switching technology - work on this subject happened independently in the UK and in USA and there was also a certain degree of sharing of ideas...

In England, at the NPL (National Physical Laboratory) Teddington site, Dr Donald Davies conceived the idea of a �network� of inter-connected data terminals where the data was broken into small chunks (or �packets� as Davies named them) rather than in a continuous stream, which also avoided the problem of short messages being blocked behind long messages

Davies� ideas were first presented in public in the USA at the ACM symposium, in Gatlinburg in 1967, and in the UK at the IFIP Congress, 1968, in Edinburgh

The NPL packet switching approach was adopted by the US Department of Defense in 1967 and in 1968 aproject called the ARPANET, the forerunner of the internet, was launched

The first ARPANET link was between the University of California and Stanford Research Institute in 1969 and the
first international ARPANET connection was made between London and Norway in 1973

In the USA efforts to interconnect computers had been going on for some time but had focussed on circuit switching rather than packet switching

In 1957, Dr. J.C.R. Licklider left MIT to join Bolt Beranek and Newnan (BBN Technologies), where he advanced the state of many basic ideas, especially the BBN Time-Sharing System

In 1959, a computer scientist, Paul Baran, was working at the RAND Corporation on the idea of interconnecting computers. In 1962, Baran presented a paper titled On Distributed Communications Networks he proposed the computer communication concept of standard message blocks routed as �hot potatoes� in a store-and-forward system

In 1961 Leonard Kleinrock wrote a proposal for his thesis at MIT on "Information Flow in Large Communication Nets" and in 1962 "Message Delay in Communication Nets with Storage" both of which described short message data techniques

In 1962, when Dr Licklider became the first Director of the IPTO (Information Processing Techniques Office) of the ARPA (Advanced Research Projects Agency), he promoted the development of time-sharing one computer at the same time and
in 1963 he proposed an even grander vision: an "Intergalactic Network" of thousands of computers, millions of computers...

In 1965, two computer scientists Dr. Lawrence G. Roberts and Thomas Marill, conducted an experiment to understand what it would take to interconnect two computers, namely a TX-2 computer at MIT Lincoln Lab with a Q-32 computer at System Development Corporation in Santa Monica CA, using a lease-line from Western Union - this experiment highlighted the complexity of the problem and concluded that circuit switching, as used by the telephone network, was a poor solution

In 1968 Dr Roberts beame the program manager for ARPANET and Wesley Clark suggested the use of dedicated computers in a message switching network, which were later called Interface Message Processors (IMPs)

The IMPs together with the telephone lines and the modems would constitute the message-switching, communications network, or "Subnet

Dr Roberts presented a paper titled Multiple Computer Networks and Intercomputer Communications at the ACM symposium, in Gatlinburg in 1967, which he down-played slow speed circuits but stated  that the communication links between IMPs would be 2400 bit/second dial-up circuits

Roger Scantlebury of NPL presented at the aforementioned Gatlinburg conference in 1967 on the local network being developed at NPL (National Physical Laboratory) in the UK by Donald Davies, which used much higher speed circuits - he also saw the US plans for ARPANET and reported back "It would appear then that the ideas in the NPL paper at the moment are more advanced than any proposed in the USA"

Dr Roberts was heavily influenced by the NPL work, stating later "The NPL paper clearly impacted the ARPANET in several ways. The name "packet" was adopted, a much higher speed was selected (50 Kilobit/second vs 2.4 Kilobit/second) for internode lines to reduce delay and generally the NPL analysis helped confirm the concept of packet switching

Here is a video of Larry Roberts (Dr. Lawrence G. Roberts) himself talking about much of the history described above, including talking to Donald Davies of NPL in the UK, about using the term "packets" and faster links (at 11:10)

The key point about the approaches taken in both England and America was that processing power almost dictated that seperate computer systems were used to handle the establishment of communcations between the main computers

Interface Message Processors (IMPs) were manufactured by  Bolt Beranek and Newnan (BBN Technologies) and were based on Honywell DDP-516 systems, with a different front panel and 6,000 words of code written by the "IMP Guys" at BBN in Honeywell 516 assembly language

The interface message processor for the ARPA computer network document written by several BBN employees, such as Robert Kahn

F.E. Heart, R.E. Kahn, S.M. Ornstein, W.R. Crowther, and D.C. Walden

J.M. McQuillan, W.R. Crowther, B.P. Cosell, D.C. Walden, and F.E. Heart, Improvements in the Design and Performance of the ARPA Network

ARPA Network Design Decisions

This point is explained in true whiteboard fashion by BBN employees in this video (at 4:30
) - IMP operation is also described, along with the size of the ARPANET in 1972 and generation of network status and statistics - A simpler version of the IMP called a TIP is also described and its use for terminal connection

The first IMP was installed at UCLA in Kleinrock�s lab and on the 29th of October 1969, the first ARPANET communication was established between with Douglas Engelbart's lab at the Stanford Research Institute (SRI), as the commemorated by the UCLA Office of Public Information below

By December 1969, the fldgeling ARPANET had grown to 4 nodes, with the connection of the University of California at Santa Barbara and the University of Utah

In 1972 the second phase of ARPANET produced a major expansion from the 4 original sites to 40 sites

1822 protocol[edit]

The starting point for host-to-host communication on the ARPANET in 1969 was the 1822 protocol, which defined the transmission of messages to an IMP.[81] The message format was designed to work unambiguously with a broad range of computer architectures. An 1822 message essentially consisted of a message type, a numeric host address, and a data field. To send a data message to another host, the transmitting host formatted a data message containing the destination host's address and the data message being sent, and then transmitted the message through the 1822 hardware interface. The IMP then delivered the message to its destination address, either by delivering it to a locally connected host, or by delivering it to another IMP. When the message was ultimately delivered to the destination host, the receiving IMP would transmit a Ready for Next Message (RFNM) acknowledgement to the sending, host IMP.

The initial version of the 1822 protocol was developed in 1969: since it predates the OSI model by a decade, 1822 does not map cleanly into the OSI layers. However, it is accurate to say that the 1822 protocol incorporates the physical layer, the data link layer, and the network layer. The interface visible to the host system passes network layer addresses directly to a physical layer device.

To transmit data, the host constructs a message containing the numeric address of another host on the network (similar to an IP address on the Internet) and a data field, and transmits the message across the 1822 interface to the IMP. The IMP routes the message to the destination host using protocols that were eventually adopted by Internet routers. Messages could store a total length of 8159 bits, of which the first 96 were reserved for the header ("leader").[11]

While packets transmitted across the Internet are assumed to be unreliable, 1822 messages were guaranteed to be transmitted reliably to the addressed destination. If the message could not be delivered, the IMP sent to the originating host a message indicating that the delivery failed. In practice, however, there were (rare) conditions under which the host could miss a report of a message being lost, or under which the IMP could report a message as lost when it had in fact been received.

Later versions of the 1822 protocol, such as 1822L, are described in RFC 802 and its successors.

Network Control Program[edit]

Unlike modern Internet datagrams, the ARPANET was designed to reliably transmit 1822 messages, and to inform the host computer when it loses a message; the contemporary IP is unreliable, whereas the TCP is reliable. Nonetheless, the 1822 protocol proved inadequate for handling multiple connections among different applications residing in a host computer. This problem was addressed with the Network Control Program (NCP), which provided a standard method to establish reliable, flow-controlled, bidirectional communications links among different processes in different host computers. The NCP interface allowed application software to connect across the ARPANET by implementing higher-level communication protocols, an early example of the protocol layering concept later incorporated in the OSI model.[55]

NCP was developed under the leadership of Stephen D. Crocker, then a graduate student at UCLA. Crocker created and led the Network Working Group (NWG) which was made up of a collection of graduate students at universities and research laboratories sponsored by ARPA to carry out the development of the ARPANET and the software for the host computers that supported applications. The various application protocols such as TELNET for remote time-sharing access, File Transfer Protocol (FTP) and rudimentary electronic mail protocols were developed and eventually ported to run over the TCP/IP protocol suite or replaced in the case of email by the Simple Mail Transport Protocol.

Sorry but there's only pictures to look at here so far - I'll add some words when I get time!!

Until then though, this TCP/IP Bible may prove useful! - Here's some more detailed info on OSPF and BGP ..... plus a Design Guide for large IP networks (covering OSPF & BGP)


In October 1972 Bob Kahn organized the first public demonstration of the ARPANET at the International Computer Communication Conference (ICCC). But perhaps more importantly this was the year that the first email was sent. In March Ray Tomlinson at BBN wrote the basic email message send and read software, motivated by the need of the ARPANET developers for an easy coordination mechanism. In July, Roberts expanded its utility by writing the first email utility program to list, selectively read, file, forward, and respond to messages. A year later the first international connections to the ARPANET were added, to the UK and Norway.

The problem was that the ARPANET wasn�t yet the Internet we know and love. The interconnections didn�t really have the flexibility needed to allow networks to be connected together- i.e. to be an �inter�-net. It was more like a large Wide area network that machines, rather than their local networks could connect to.

The man who first realised the need for an �open architecture� was Bob Kahn of BBN. Each network would look after its own internal workings and black boxes called �gateways� would deal with passing packets between the networks. There would be no global control or error recovery provided by the gateways.

At the start of 1973 Kahn asked Vinton Cerf, then a researcher at Stanford, to work with him on the detailed design of a protocol. Cerf had been involved in the design of the initial ARPANET�s original protocol. What they created and issued as a specification in 1974 we now call TCP/IP.

It took almost ten years before the ARPANET was ready to switch over to TCP/IP. On January 1st 1983 the whole of the ARPANET changed to TCP/IP and any hosts who didn�t make the change were left out in the cold. At the same time the military sites on the ARPANET took the opportunity to split off and merge with the new Defence network to become MILNET.

In the same year the Domain Name Server (DNS) was developed at the University of Wisconsin. This allowed users to refer to sites by name and became the largest distributed database ever. By the following year DNS was introduced to the network and it had over 1000 hosts � small by today�s standards.


Bob Metcalfe's paper on Packet Communication for MIT

Bob Metcalfe's article on Distributed Packet Switching