Networks have formed an infrastructure for communication since the formation of telegraph networks. Networks allow for the distribution and sharing of information between numerous users. In terms of computing networks allow for the distribution and sharing of resources, plus the ability to share and manipulate data over distances, and have allowed for the introduction of other communications methods such as email, and more recent developments such as voice over IP.
Networks consist of a transmission medium that forms its basic infrastructure. Local area networks that extend no further than an office block or a school for example could use shielded twisted pair or coaxial cable to form its basic infrastructure. Data is sent down these wires in a similar way that data is communicated using the Internet. Another transmission for such a network may also be wireless that adopts radio frequencies to transmit data to machines with wireless receivers. Wide area networks, which is the best term used to describe the internet and, networks within corporate companies that extend internationally use a mixture of transmission mediums, possibly including such technologies as satellite, fibre optics and radio.
Protocols are adopted within networks to allow computers to communicate. As the name suggests protocols are standard methods for achieving a specific behaviour. The protocols operate in a layered network model or protocol stacks. The layers are as follows:
- Application
- Transport
- Internet
- Network
The concept of the specification of such a model is that each layer can easily be upgraded or replaced if necessary, it helps to promote the durability of the network model. This applies to certain protocols as well, the TCP (Transmission Control Protocol) was designed specifically to work across dissimilar networks and unreliable connections, so in the event of an attack, or war nothing would disrupt the communications system between computers.
TCP and UDP are two important protocols that exist within the transport layer. Transmission control protocol is a connection-oriented protocol that ensures the delivery of data along a packet switched or virtual circuit network. UDP is a connectionless protocol that has no inbuilt reliability features. UDP is especially important in modern computing, as it is capable of handling time-based media. That is information that changes meaningfully with respect to time; this encompasses video and audio streaming and other similar technologies.
The Internet protocol specifies the format of packets within networks and the addressing scheme. TCP or UDP are usually combined with IP to form TCP/IP and UDP/IP connections respectively. Regardless of the network being packet switched or a virtual circuit, data is still required to be sent in packets to allow routers to be able to handle them. The difference is the connection, while the packet switched network will reassemble packets back in the correct order each packet can travel many different routes to reach its destination. A virtual circuit creates a single route for the packets to travel. A virtual circuit promotes reliability, speed and increased packet sizes.
The network layer describes the type of network. For example wireless, bluetooth or Ethernet. Each type of network has its own particular behaviour, for example bluetooth is an ad hoc network that can be created by simply being in proximity to another bluetooth device. Ethernet is a physical network. The Ethernet protocol describes how to handle the physical aspect, and data transfer within this network.
References
www.ciscopress.com - accessed 28th January 2005
www.ieee-virtual-museum.org - accessed 28th January 2005
www.webopaedia.org - accessed 28th January 2005
www.marconicalling.com - accessed 28th January 2005
Bibliography
Bates, C. (2003). Web Programming, Building Internet Applications. John Wiley & Sons
Tanenbaum, A, S. (1996). Computer Networks. Prentice-Hall