infoARPA

The Childhood of Internet

 
 

Block Diagram and Protocol Stack

Technical Overview

A plausible layout of the ARPANET Hosts and terminals "talk" with each other via the IMP-subnet.

The ARPANET's purpose was to provide fast, reliable communication between heterogeneous host machines. To accomplish this goal, ARPA determined that the use of the currently established line switching facilities would be economically and technically inefficient. Unlike the line switched network, the ARPANET would be a message switched network. The ARPA network is designed so that messages may traverse any of several paths to reach their destination. The research computers at each node would be connected to these identical processors, which are called Interface Message Processors, or IMPs.

The ARPANET was designed to have a reliable communications subnetwork. It was to have a transmission delay between hosts of less than ½ second. Hosts will transmit messages, each with a size up to 8095 bits. The IMPs will segment messages into packets, each of size up to 1008 bits. These packets will be transmitted in parallel via routes determined by a distributed adaptive routing algorithm to reduce delay. All of this is described in their sections in the tour.

ARPAnet Protocol Stack

Because of the IMPs, the ARPANET can be thought of as two distinct parts. The first being the IMP subnet and the second being the protocols The IMP subnet provided an invisible means of transmitting messages from a source host to a destination host.

Protocols

The structure of the ARPANET logically appears as a layering of protocols. These protocols would be the IMP-IMP, the Host-IMP, and the Host-Host protocols.

 

 

 

 



Make a comment on this topic..