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. 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").
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.
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.
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.
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