The history of Networking
Mainframe computers in the 1960s were stand-alone machines. They performed computing jobs based on input (usually on punched cards or tapes) and created output, usually on printed paper. Mainframe computers were large expensive systems typically in use at universities and large corporations. Since a university or corporation had only one computer (the mainframe), there was little need to have networking.
Even with time sharing systems like the early UNIX systems in the 1970s the user's terminals or teletypes were connected to the central computer through serial (RS-232) lines.
ARPANET and Internet
In the late 1960s, some computers were connected by means of the ARPANET – the predecessor of the Internet. The ARPANET network consisted of small Interface Message Processors (IMPs) which we would now call network routers.
The IMPs performed store-and-forward packet switching functions, and were interconnected using modems that were connected to analog leased lines. The computers were connected to the IMPs via serial interfaces (RS-232).
ARPANET originally used the Network Control Protocol (NCP), which was replaced by TCP/IP in 1983. The first e-mail system via ARPANET was implemented back in 1971, and by 1973, the File Transfer Protocol (FTP) was defined and implemented, enabling file transfers over the ARPANET.
Also in 1973, engineers started to connect the ARPANET to the packet radio network (PRNET) and the Satellite Network (SATNET). They called the connection between these networks inter-networking, or the Internet for short.
The Internet grew at an incredible rate in the following years, especially after the rise of the WWW for which the Hyper Text Markup Language and the HTTP protocol was invented in 1990. The Internet became available for the average business and home user around 1996. This also had a lot to do with Windows 95, which was a game changer: it came with a web browser. It is estimated that today, the Internet interconnects more than 2 billion computers.
When Personal Computers (PCs) found their way into the office, the need arose for sharing data between office PCs. Local Area Networks (LANs) were designed to allow PCs to connect to each other and to shared resources like a file server, a printer or a router to the Internet.
In the early years LANs were built using technologies like ARCNET, Token Ring, Ethernet and others. Most of these technologies are phased out now and today Ethernet is the norm for LANs.
ARCNET was introduced in 1977 by Datapoint corporation and was the first widely available LAN networking system, years before the introduction of the IBM PC. ARCNET transmitted packets of data at 2.5 Megabit per second (Mbit/s). It was one of the first LAN technologies to makes no assumptions about the type of computers that could be connected, in contrast with for instance SNA or DECnet. ARCNET was less expensive than Token Ring and Ethernet, more reliable, more flexible, and by the late 1980s it had a market share about equal to that of Ethernet.
Token Ring was a LAN technology created by IBM in 1985. Token Ring uses a ring topology whereby the data is sent from one machine to the next and so on around the ring until it ends up back where it started.
Token Ring originally ran at a speed of 4Mbit/s, later upgraded to 16Mbit/s, which was significantly faster than ARCNET and Ethernet at the time.
Token Ring was a very reliable protocol that allowed for a very high utilization of the available bandwidth (up to 90%), as opposed to Ethernet that could be utilized to 60% max.
Mainly because of the cost and the complex physical components Token Ring networks are now mostly extinct, taken over by Ethernet networks.
Ethernet was developed at Xerox PARC between 1973 and 1975 by a team led by Robert Metcalfe. Metcalfe later founded 3Com that built the first 10 Mbit/s Ethernet adapters in 1981.
Ethernet originally employed a shared medium topology, based on coax cable. All machines were connected to a single, shared Ethernet cable that ran round a building, connecting each machine. Later Ethernet used twisted pair cabling with hubs and switches to decrease the vulnerability of the network due to broken cables or bad connectors.
Ethernet is also the basis for Wi-Fi. Today’s speeds are 100Mbit/s or 1 Gbit/s for wired Ethernet and 300 Mbit/s for wireless Wi-Fi.
Commercial Wide Area Networks (WANs) started to appear in the 1980s when organizations started to need a network connection to their subsidiaries and (sometimes) to other organizations. The first WANs consisted of point-to-point connections using modems and the analog public telephone system. The modems were connected to routers that routed the data packets between the end points.
Later, telecom providers started to offer dedicated analog leased lines. These leased lines eliminated the need to setup a call and were considerably cheaper in use than dial-up lines. When more and more WAN connections appeared, telecom providers started to offer digital leased lines. Digital leased lines like T1/E1 lines and ISDN (Integrated Services Digital Network) provided higher bandwidths because they eliminated the need for modems to convert digital data to analog frequencies that would fit the characteristics of telephone conversations.
Most WAN connections today are based on packet switching technologies, in which devices transport packets via a virtual point-to-point link across a carrier network. Packet switched networks are very reliable and provide robust WAN connections.
This entry was posted on Zaterdag 09 Oktober 2010