Communications Networks
What is a Network? <ul><li>An arrangement of two or more computers interconnected to enable sharing of resource and data. ...
Advantages of Networks <ul><li>Sharing of data </li></ul><ul><li>Sharing of resources </li></ul><ul><ul><li>hardware and s...
Servers <ul><li>A server is a computer that is designed to support a computer network. </li></ul><ul><li>File Server </li>...
Networks <ul><li>LANS - Local Area Networks </li></ul><ul><li>MANS - Metropolitan Area Networks </li></ul><ul><li>WANS - W...
LANS <ul><li>Restricted area - room, building. </li></ul><ul><li>Privately owned transmission systems - cable based media....
LANs - peer to peer <ul><li>LANs do not have to use a single server but may use a peer to peer network. </li></ul><ul><li>...
MANS <ul><li>Network spans a municipality. </li></ul><ul><li>Transmission is left to Public Access Utility Carriers (Telst...
WINS <ul><li>High speed communications among PC’s and other equipment within one site. </li></ul><ul><li>Use radio frequen...
The Internet <ul><li>The internet is a worldwide network of computer networks. </li></ul><ul><li>The Internet has millions...
Network Topologies <ul><li>STAR </li></ul><ul><li>RING </li></ul><ul><li>BUS </li></ul>
STAR <ul><li>Each node is connected to the network controller (or host) by a separate transmission medium.  </li></ul><ul>...
STAR NETWORK Server Nodes
Star network <ul><li>Expensive  </li></ul><ul><ul><li>due to amount of cabling </li></ul></ul><ul><li>Other nodes can cont...
BUS Network <ul><li>A single link (the bus) traversing the area of the network. Each node is tapped into the passing bus l...
BUS NETWORK <ul><li>ETHERNET is the most common example of the bus. </li></ul>
Bus network <ul><li>Usually uses twisted pair or coaxial cable. </li></ul><ul><li>Easy to add extra nodes. </li></ul><ul><...
RING NETWORK <ul><li>A number of point-to-point links between nodes with the first and last being joined to form a loop. <...
Ring Network
Ring Network <ul><li>A common type of ring network is the TOKEN ring network. </li></ul><ul><li>Nodes that want send data ...
Ring Network <ul><li>The token is attached to the message  and when received correctly an acknowledgement signal is sent b...
Ring Network <ul><li>Data only travels in one direction. </li></ul><ul><li>Requires medium access control. </li></ul><ul><...
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Networks

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Networks

  1. 1. Communications Networks
  2. 2. What is a Network? <ul><li>An arrangement of two or more computers interconnected to enable sharing of resource and data. </li></ul><ul><li>A true network is characterised by having its processing distributed across the various processors which constitute the network itself. </li></ul>
  3. 3. Advantages of Networks <ul><li>Sharing of data </li></ul><ul><li>Sharing of resources </li></ul><ul><ul><li>hardware and software </li></ul></ul><ul><li>Communication </li></ul><ul><li>Easier resource management and security. </li></ul>
  4. 4. Servers <ul><li>A server is a computer that is designed to support a computer network. </li></ul><ul><li>File Server </li></ul><ul><ul><li>an entire file is sent to the requesting computer and it does the processing. </li></ul></ul><ul><li>Client Server </li></ul><ul><ul><li>processing is done on the server before the file is transmitted. </li></ul></ul>
  5. 5. Networks <ul><li>LANS - Local Area Networks </li></ul><ul><li>MANS - Metropolitan Area Networks </li></ul><ul><li>WANS - Wide Area Networks </li></ul><ul><li>WINS - Wireless In-building Networks </li></ul>
  6. 6. LANS <ul><li>Restricted area - room, building. </li></ul><ul><li>Privately owned transmission systems - cable based media. </li></ul><ul><li>Doesn’t cross public roads. </li></ul><ul><li>High transmission rate. </li></ul>
  7. 7. LANs - peer to peer <ul><li>LANs do not have to use a single server but may use a peer to peer network. </li></ul><ul><li>Peer to peer networks allow any computer to share the resources with any other computer on the network. </li></ul><ul><ul><li>Microsoft's Home Networking and Apple’s AppleTalk are examples of this. </li></ul></ul>
  8. 8. MANS <ul><li>Network spans a municipality. </li></ul><ul><li>Transmission is left to Public Access Utility Carriers (Telstra) </li></ul><ul><li>Area covers a town, city or bigger. </li></ul>WANS
  9. 9. WINS <ul><li>High speed communications among PC’s and other equipment within one site. </li></ul><ul><li>Use radio frequency that can carry a large amount of data at high speed. </li></ul><ul><li>Possible security problems. </li></ul>
  10. 10. The Internet <ul><li>The internet is a worldwide network of computer networks. </li></ul><ul><li>The Internet has millions of users and can be used for: </li></ul><ul><ul><li>email, file transfer, research, discussion groups and entertainment </li></ul></ul>
  11. 11. Network Topologies <ul><li>STAR </li></ul><ul><li>RING </li></ul><ul><li>BUS </li></ul>
  12. 12. STAR <ul><li>Each node is connected to the network controller (or host) by a separate transmission medium. </li></ul><ul><li>All communication between nodes must first be directed to the controller where it is re-addressed. </li></ul><ul><ul><li>e.g. PABX, Time sharing Main Frame </li></ul></ul>
  13. 13. STAR NETWORK Server Nodes
  14. 14. Star network <ul><li>Expensive </li></ul><ul><ul><li>due to amount of cabling </li></ul></ul><ul><li>Other nodes can continue if one link is broken. </li></ul><ul><li>No contention for access to lines. </li></ul><ul><li>Capacity of network determined by the speed of the controller. </li></ul>
  15. 15. BUS Network <ul><li>A single link (the bus) traversing the area of the network. Each node is tapped into the passing bus line forming a multidropped configuration. </li></ul><ul><li>All nodes share a common transmission medium. </li></ul><ul><li>Messages and destination address are broadcast to all nodes, but only the addressee accepts it. </li></ul>
  16. 16. BUS NETWORK <ul><li>ETHERNET is the most common example of the bus. </li></ul>
  17. 17. Bus network <ul><li>Usually uses twisted pair or coaxial cable. </li></ul><ul><li>Easy to add extra nodes. </li></ul><ul><li>Easy installation. </li></ul><ul><li>Performance degrades if network gets busy. </li></ul><ul><li>Requires medium access control. </li></ul><ul><li>Usual transmission speed 10Mbps. </li></ul>
  18. 18. RING NETWORK <ul><li>A number of point-to-point links between nodes with the first and last being joined to form a loop. </li></ul><ul><li>Each node shares the transmission line. </li></ul><ul><li>Each message must be addressed. </li></ul>
  19. 19. Ring Network
  20. 20. Ring Network <ul><li>A common type of ring network is the TOKEN ring network. </li></ul><ul><li>Nodes that want send data must first get the token (an electronic signal) to gain access to the communication channel. </li></ul>
  21. 21. Ring Network <ul><li>The token is attached to the message and when received correctly an acknowledgement signal is sent back. </li></ul><ul><li>The token is then released back onto the network. </li></ul><ul><li>Only one token is available at any one time. </li></ul>
  22. 22. Ring Network <ul><li>Data only travels in one direction. </li></ul><ul><li>Requires medium access control. </li></ul><ul><li>Typical speed 1-10Mbps </li></ul>

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