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