Switches – Unlike Hubs, switches are able to read packets and send them to a specific location within a network, this makes it faster and more efficient. Switches will be used for the insurance companies networking solution.
Repeaters – A repeater is a device that regenerates a signal, it does not just boost the signal; when a signal is received by a repeater it is inspected and then recreated and sent on, and this allows the signal to be sent long distances without errors. The difference between a repeater and an amplifier is that amplifiers boost the signal along with any noise or interference that the signal has picked up. Repeaters could be used within the insurance company, to strengthen the communication within it’s WAN.
Bridges – Using a bridge enables different segments of a LAN (using the same protocol) to be connected; for example different departments within a company may be on separate LANs but may need to interact with other departments, this would be possible by connecting the separate LANs together using a bridge, this reduces the amount of traffic on a network. Because the insurance company has three segments (Sales, Claims and Finance) and they all need to communicate with each other it would be a good idea to connect the segments using bridges.
Task 2.A
Network Topologies
Network Topologies that could be utilised for the insurance company:
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Star – When using a star topology all devices on the network are individually connected to a hub or switch this means that if there is a cable failure it will only affect one of the workstations and not the entire network. However, if there is a failure with the hub or switch the whole network will be affected.
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Bus – This topology uses a backbone to connect all nodes within a network, all devices are connected to the main cable; data is passed onto the main cable and is available to all devices, only the device that the message is intended for retrieves and processes the message. If a cable connecting a device to the backbone fails then that particular device will fail, however, if the cable used as the backbone fails then the entire network will be useless.
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Mesh – Mesh topology is extremely effective because each device is directly connected to every other device. When data is broadcast this topology decides which route is the quickest and easiest route for the message to take. Using this topology means that there are always alternative routes for the data to travel down if cables fail. Although extremely effective, a full mesh is usually not needed and therefore a partial mesh is used; this is when each device is indirectly connected to the other devices.
How these topologies would be used within the insurance company:
The insurance company has three main departments (Sales, Claims and Finance). There is a lot of communication within the departments. There is not as much communication between the departments; however, they do need to communicate. The company is part of a WAN with ten other branches around the country that they need to communicate with regularly.
Company LAN
The insurance company could use either star or bus topology for their LAN network. I would recommend that they use star as it is more reliable than bus. Each of the departments should be on a separate star topology. Each topology will use a switch as the central connection device and each of the department networks should be connected to each other using bridges to allow communication between departments. The switch allows each department to communicate effectively within that department as the switch can identify the destination of each message, therefore, making it faster than using a hub. Using bridges will enable each department to communicate with each other.
Company WAN
The company could use a partial mesh for their WAN network, this means that each branch’s LAN network can communicate with every other branch fastly and effectively, also, cable errors or failures will not effect the network in a major way because there are other routes for the data to take; For example if ‘H’ were sending a message to ‘I’ there are six different routes that the message could be sent on. It would also be advisable for the company to use repeaters as this will ensure that over long distance the quality of the signal (and message received) are not affected.
Task 2.B
Packet Switching
- If a message exceeds the networks maximum length it is broken up into packets and then reassembled when received.
- A packet contains three fields; these are header, tail and data fields. A header field contains the senders address, destination of the message, packet size and sequence number. The tail field includes error checking information.
- The packet is multiplexed on to a wire (multiplexing means that different data streams are transmitted together on one data line).
- At each device the packet is received, stored for a very short space of time and then passed on until it is retrieved by the device it was intended for.
- This network service uses Asynchronous Transfer Mode (ATM); this is a protocol which encodes all the traffic being sent into cells which are a fixed size, this ensures that no single type of data uses the wire more than another.
If the insurance company were to use this type of network service it would optimise the use of the company’s bandwidth; this is because it is shared by all devices at all times. Data is not sent over a specific line, messages are sent over what ever line would be the quickest route (i.e. the route with the least traffic). The time delay in which data is sent and received is minimal when using this service because each packet contains destination information and therefore each packet knows where it is going, thus making transmission faster. Because each packet contains header and tail information there is an overhead when sending data, however, including a header makes transmission more effective because it allows the devices in a network to decide the best route for the data to take. There are few errors because of the tail field with error checking information. This would be suitable for the company to use for their WAN network.
WAP (Wireless Application Protocol)
- WAP is used for wireless communication, the main purpose of using this service is to allow mobile phones and PDAs to connect to the internet.
- WAP simplifies data in order for it to be viewed via a mobile phone. It uses WML (Wireless Mark Up Language) to do this. The data needs to be simplified because mobile phones do not have the processing powers of computers and therefore could not handle the amount of data and graphics on a typical website.
- There are four parts to WAP; these are:
- Wireless Application Environment – This is the part of the WAP that is visible to the user.
- Wireless Session Protocol – This establishes a connection with a ‘WAP enables’ website and closes the connection.
- Wireless Transfer Protocol – This part of the WAP ensures that data is sent to the correct place.
- Wireless Layer Transport Security – When data is being sent from a PDA or mobile phone this part of the WAP compresses the data and encrypts it.
The insurance company could use this service to enable their sales advisors to connect to their network from outside of the office. The way in which this would work is sales advisors would connect to a wireless network using mobile phones or PDAs, they would then request a website, this request will be passed on to a gateway, the gateway will convert the request to HTML format and send it to the website, the website then send the content back to the gateway where it is converted back to WML, and finally the page is displayed on the device. This is a very slow network service compared to packet switching, however it can be very useful, and, although there are limitations to what can be viewed on the internet, the basic functions needed, can be carried out, e.g. e-mail.
