• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Network Communications.

Extracts from this document...

Introduction

Network Communications The main features of a range of transmission media and modes of data transmission on a network TRANSMISSION MEDIA The form of communication link used to communicate between two or more stations. EG. Radio/TV broadcasts, copper cable (twisted pair/coax), fibre optic (FDDI), microwave, infra-red, satellite, cellular telephone network. Each device on a network is connected to a transmission cable to allow messages to be sent from one device to another. LANs typically use: * Twisted pair * coaxial * fibre optic The differences between these media relate to: * cost * ease of installation * speed/capacity * distance * resistance to interference * reliability Networks can also use wireless media such as: * microwave * radio frequencies which do not require a physical link. MODES TRANSMISSION There are several configuration settings which affect the mode of transmission. Flow control and cable provisions affect the type of exchanges between stations. Simplex is a one-way mode of transmission; duplex is two way; half duplex enables two-way transmission but not for each station simultaneously; asymmetric duplex is two-way but with different speeds each way. Asynchronous transmission sends a character at a time with markers either end; synchronous systems are used to speed up this process and send whole blocks of data at a time by timing the start and end of the block. ...read more.

Middle

Token Ring interconnects PCs via special twisted-wire cable in a star topology, connecting all computers to a central wiring hub. CSMA/CD (Carrier Sensing Multiple Access with Collision Detection) A LAN contention protocol by which workstations connected to the same channel are able to sense transmission activity on that channel and so defer their own transmission while the channel is active. If two nodes try to transmit simultaneously a collision is detected and both stations stop transmission for a period. After a random period of time each station will make a repeat attempt. It is unlikely that they will attempt to transmit at the same time and further collision usually does not occur. Wide Area Network (WAN) A WAN connects computer networks or devices that are located in different geographical areas. A WAN uses world-wide communications usually telephone lines, to connect computer resources. A WAN may connect similar computer systems (LANs to LANs) or dissimilar systems (LANs to mini computers or mainframes) A WAN provides communication speeds at usually less than 2Mbps (a common communication line is called T1 that gives 1.544Mbps) Higher speed lines are available for WANs but those are provided by the telephone companies at a very high price. ...read more.

Conclusion

The implication is that packets belonging to other messages may be sent between the packets of the message being sent from A to D. This provides a much fairer sharing of the resources of each of the links. 2. Another benefit of packet switching is known as "pipelining". Pipelining is visible in the figure above. At the time packet 1 is sent from B to C, packet 2 is sent from A to B; packet 1 is sent from C to D while packet 2 is sent from B to C, and packet 3 is sent from A to B, and so forth. This simultaneous use of communications links represents a gain in efficiency, the total delay for transmission across a packet network may be considerably less than for message switching, despite the inclusion of a header in each packet rather than in each message. Meaning of bandwidth and the impact of bandwidth on data transmission Bandwidth has a general meaning of how much information can be carried in a given time period (usually a second) over a wired or wireless communications link. For example, a link with a broad bandwidth - that is, a broadband link - is one that may be able to carry enough information to sustain the succession of images in a video presentation. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Information Systems and Communication section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Information Systems and Communication essays

  1. Free essay

    This research report will present a brief history of the Internet, focusing on some ...

    a 32 digit number known as an IP address and if computers wanted to connect to each other this numerical address was required. Still today the Internet is based on IP addresses; nonetheless instead of having to remember numerous 32 digit series we are able to insert alphabetical addresses.

  2. Information: G061 - Systems and Communication

    ensures an adequate level of protection for the rights and freedoms of data subjects in relation to the processing of personal data Individuals have certain rights: - right to subject access - right to prevent processing likely to cause damage or distress - right to prevent processing for the purpose

  1. Computer Network

    This is a family of frame-based computer networking technologies for LANs. WAN, or wide area networks, are broader geographic networks, like one city to another. They are more of a collection of interconnected LAN networks. Other WANs, provided by service providers, connect local networks to the Internet.

  2. BTEC Unit 8: The Theory of Data Communications

    Types of mobile commutation devices would be third (3G) and fourth (4G) generation cellular phones, wireless laptops and wireless PDAs. Wireless networks use the 802.11x standard. This is the IEEE standard (Institute of Electrical and Electronics Engineers) which defines the speed of the network and its range.

  1. Unit 5 - Communications Technology

    Because multiple stations share the ring, medium access control is needed to determine at what time each station may insert frames. 3. Star Topology Star topology devices are all connected to a central HUB or concentrator. This is the most commonly used physical cabling network topology today.

  2. Unit 14 - School of Computing

    we do our utmost best to provide best possible service as well as taste in curries. We have to make sure that we don't loose any of our regular customers and try to increase the level of business by providing curries on special offers or decrease the prices.

  1. Cunha & Ribeiro Ltd: Stock Control & Invoice Database

    Also another problem he has told me is that he hasn't got an efficient system to record delivery times, and has to write all of the invoices by hand which are time consuming for both him and his customers. Lastly, his existing system of storing customer details on paper and

  2. Using ICT to communicate

    The front cover has the company logo "AQA Teacher support" in the top right hand corner of the page, in the top left hand corner of the page is a section of text at a slanted angle informing the reader of the time period the meeting will be held "Jun-Dec".

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work