A Network is a number of computer systems connected together.
Unit 3 - Network
Advantages
Share peripherals such as printers.
Share Software
Share data/files.
Easier for internal communication/ can send email
Centralised backup
Easier to monitor network activity
Centralised maintenance (manage the network from one location)
Can access data from any computer
Disadvantages
Bus
The computers are connected to a single cable on which data can be sent, called the bus.
The bus has terminators on each end, which are needed to close each end of the cable.
As the packets arrive at each computer system, it checks the destination address contained in the packet to see if it matches its own.
If the address does not match, the computer system ignores the packet. If the address of the computer system matches that contained in the packet, it processes the data.
Transmission of data
Ring
Each node connects to exactly two other nodes, providing a single pathway for signals through each node
Star
advantages and disadvantages
Good performance/fast network speed
Easy to set up
Easy to add more computer systems
without taking the network down
failure of workstations will have no
effect on the network
Minimal network collisions
Better security
Expensive to install as more cable is required
Extra hardware required, such as a hub
Sending data over a Star network
Computer A adds computer D’s address to packet
Computer A sends packet to switch
Switch looks at address on packet
Switch compares to stored list of addresses on network
Switch forwards packet to computer D’s address
Circuit swtiching - old method of transferring data, very slow. Direct
if the server gets hacked all computers are at risk and hackers can access the data easier
Disadvantages
Data collisions are common
Disadvantages
If the cable fails or a computer fails the whole server falls down
If you want to add another computer to the network you have to completely redo and take apart the old network
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Packet switching- new method of transferring data. It splits the data into packets before transmission, packets are then sent in order but might arrive out of order. Each packet can take a different route to its destination, data is then reassembled at the destination.
Data packets contents
length is the number of bits in the packet
packet ID is needed so that afterwards the data from multiple packets can be arranged into the correct order.
Source address is the IP address of the device that sent the data.
Destination address is the IP of the device that should receive the data.
Protocol is an indication of which protocol (HTTP, FTP, SMTP, etc.) has been used to form the packet.
Data is the reason a packet is being sent in the first place. Eventually, all packet components are discarded except for the data itself.
Checksum is a technique that verifies that the data was sent matches the data was recieved.