Data Transmission Flashcards
What is a LAN?
Local Area Network.
Short geographical range. Computers close together.
More secure that WAN.
What is a WAN?
Wide Area Network.
Long geographical range. All over the world. eg. internet
Insecure compared to LAN
State the 8 advantages of networks.
State the disadvantages of networks.
- It costs more money to build a network than it does standalone machines.
- There is an additional support cost that is not insignificant. Specialists are needed.
- Networks have machines in different locations, each of which potentially could be used to gain access to the server’s hard disk and the data stored on it.
- If the server on a client-server network goes down, the whole network will be out of action.
What is a bus topology?
If the cables breaks the full thing stops working.
The cable can only carry one message at a time. If the cable isn’t busy then a station can put its message on the cable. If there is a message on the cable then it waits until it is free.
Stations can also detect when these collisions have occurred. When they do detect a collision, the stations involved are asked to re-send their messages.
What is a ring topology?
This gives a better performance than a bus network, but is not as fast as a star network.
There is a security problem with both bus and ring networks. When a message is sent, it is put on the cable. All stations can read all the messages on the cable and this means that someone who has access to the network with the right software can ‘grab’ packets of information that they are not entitled to.
What is a star topology?
This kind of network is very secure because all of the communications go from one station to the target station via the server and other stations cannot ‘grab’ the communication.
Security can be managed from one central point - the server.
This kind of network takes up a lot of cable compared to a bus network and this can be expensive.
In this kind of network, the server polls each station to see if it has anything to send.
What is polling?
Polling is when the server goes from one station to the next in turn, checking if it needs to be serviced. If the server finds a station that needs to send a message, for example, then it will deal with it.
