Computer networking

Network cards such as this one can transmit data and receive at high rates over various types of network cables. This card is a 'Combo' card which supports three cabling standards.

This redirect is about computer networking, the discipline of engineering computer networks. For the article on computer networks, see Computer network.

Computer networking is the engineering discipline concerned with communication between computer systems or devices. Such communicating computer systems constitute a computer network and these networks generally involve at least two devices capable of being networked with at least one usually being a computer. The devices can be separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances (e.g. via the Internet). Computer networking is sometimes considered a sub-discipline of telecommunications, and sometimes of computer science, information technology and computer engineering. Computer networks rely heavily upon the theoretical and practical application of these scientific and engineering disciplines.

A computer network is any set of computers or devices connected to each other. Examples of networks are the Internet, a wide area network that is the largest to ever exist, or a small home local area network (LAN) with two computers connected with standard networking cables connecting to a network interface card in each computer.

History

Before the advent of computer networks that were based upon some type of telecommunications system, communication between calculation machines and early computers was performed by human users by carrying instructions between them.

In September 1940 George Stibitz used a teletype machine to send instructions for a problem set from his Model K at Dartmouth College in New Hampshire to his Complex Number Calculator in New York and received results back by the same means. Linking output systems like teletypes to computers was an interest at the Advanced Research Projects Agency (ARPA) when, in 1962, J.C.R. Licklider was hired and developed a working group he called the "Intergalactic Network", a precursor to the ARPANet.

In 1964, researchers at Dartmouth developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at MIT, a research group supported by General Electric and Bell Labs used a computer (DEC's PDP-8) to route and manage telephone connections.

Throughout the 1960s Leonard Kleinrock, Paul Baran and Donald Davies independently conceptualized and developed network systems which used datagrams or packets that could be used in a packet switched network between computer systems.

In 1969 the University of California at Los Angeles, SRI (in Stanford), University of California at Santa Barbara, and the University of Utah were connected as the beginning of the ARPANet network using 50 kbit/s circuits.

Computer networks, and the technologies needed to connect and communicate through and between them, continue to drive computer hardware, software, and peripherals industries. This expansion is mirrored by growth in the numbers and types of users of networks from the researcher to the home user.

Today, computer networks are the core of modern communication. The scope of communication has increased significantly in the past decade and this boom in communications would not have been possible without the progressively advancing computer network.

Networking methods

Networking is a complex part of computing that makes up most of the IT Industry. Without networks, almost all communication in the world would cease to happen. It is because of networking that telephones, televisions, the internet, etc. work.

There are two (broad) types of networks in existence at the moment. These are:

Local Area Network (LAN)

A Local Area Network is a network that spans a relatively small space and provides services to a small amount of people. Depending on the amount of people that use a Local Area Network, a peer-to-peer or client-server method of networking may be used. A peer-to-peer network is where each client shares their resources with other workstations in the network. Examples of peer-to-peer networks are: Small office networks where resource use is minimal and a home network. A client-server network is where every client is connected to the server and each other. Client-server networks use servers in different capacities. These can be classified into two types: Single-service servers, where the server performs one task such as file server, print server, etc.; while other servers can not only perform in the capacity of file servers and print servers, but they also conduct calculations and use these to provide information to clients (Web/Intranet Server). Computers are linked via Ethernet Cable, can be joined either directly (one computer to another), or via a network hub that allows multiple connections.

Wide Area Network (WAN)

A Wide Area Network is a network where a wide variety of resources are deployed across a large domestic area or internationally. An example of this is a multinational business that uses a WAN to interconnect their offices in different countries. The largest and best example of a WAN is the Internet, which is the largest network in the world.

A Wide Area Network involves communication through the use of a wide range of different technologies. These technologies include Point-to-Point WANs such as Point-to-Point Protocol (PPP) and High-Level Data Link Control (HLDC), Frame Relay, ATM (Asynchronous Transfer Mode) and Sonet (Synchronous Optical Network). The difference between the WAN technologies is based on the switching capabilities they perform and the speed at which sending and receiving bits of information (data) occur.

Point-to-Point WANs

A Point-to-Point WAN operates synchronously and asynchronously. Synchronous refers to the ordered transmission of a bit stream in which the speed and time at both the sending and receiving end are virtually equal. In synchronous communications, devices automatically adjust their speed accordingly. Transitions are examined between voltage states on the link.

Asynchronous transmission is the lack of imposed time ordering on a bit stream, also, there are no checks or adjustments made for a particular rate of speed. The clock source is the device that signals the other devices to which rate they should adjust their speed and is used for synchronous transmission only.

The term Data Service Unit (DSU) and Channel Service Unit (CSU) is used as an interface between the Telco (or ISP) and the customer premise. In some cases, the CSU and DSU will be owned by the customer premise. Equipment that is owned by the customer premise is called the Customer Premise Equipment (CPE). However, in many other cases the telco will only provide the equipment for leasing or will have it on site at their location. A serial interface is used between a router and the CSU(DSU), the telco will have a line attached to the CSU(DSU) and will have a very similar configuration for the router on the other end of the link. This establishes what is called a point-to-point WAN link. The CSU is considered to be the data communications equipment (DCE) which provides a clocking signal to the routers (the DTE) so that the routers send and receive data at the correct rate. The device which is receiving the clocking is referred to as the DTE or the data terminal equipment. Typically, the DSU is the router, however the DSU and CSU terms are used interchangeably.

For routers on both ends of the link to communicate, DTE and DCE serial cabling is used. A cross-connection must be made between the DTE and DCE serial cables. The effective term is essentially the exact same as the cross-over cable used in ethernet communications. To transmit and receive to take full advantage of full-duplex communications, the DTE cable swaps transmit (Tx) and receive(Rx) pairs with the DCE cable.

[Router 1 ]------- [DTE Serial]------Swap Tx and Rx------[DCE Serial]-------[ Router 2 ]

The four-wire circuit is a line from the telco with four wires in two twisted pairs. One pair of wire is used to transmit and the other pair is used to receive. Sending and receiving information at the same time is called full-duplex communication.

Point-to-Point WANs operate at speeds ranging from T1 1.544 Mbps (Megabits per second) and upwards. Europe offers speeds of 2.048 Mbps called E1 and upwards. Essentially, E1 uses 32 64-kbps (kilobits per second) channels and T1 uses 24 64-kbps channels.

For more information on WANs, read articles on Frame Relay, ATM and Sonet.

Wireless Networks (WLAN, WWAN)

A wireless network is basically the same as a LAN or a WAN but there are no wires between hosts and servers. The data is transferred over sets of radio transceivers. These types of networks are beneficial when it is too costly or inconvenient to run the necessary cables. For more information, see Wireless LAN and Wireless wide area network

In order for communication to take place between computers, mediums must be used. These mediums include Protocols, Physical Routers and Ethernet, etc. This is covered by Open Systems Interconnection which comprises all the processes that make information transport possible.

Network topologies

Main article: Network topology

Suggested topics

See the List of suggested topics for computer networking research.

References

• Larry Peterson, Computer Networks (ISBN 1-55860-832-X).
• Andrew S. Tanenbaum, Computer Networks (ISBN 0-13-349945-6).
• Important publications in computer networks
• Vinton G. Cerf "Software: Global Infrastructure for the 21st Century"

External links

• Easy Network Concepts (Linux kernel specific)
• Computer Networks and Protocol (Research document, 2006)
• Computer Networking Glossary
• Networking at Curlie