103 – Networks Assessment

There are two methods of sending Fill in the blank 1 of 15 across a network, circuit switching and packet switching.

With circuit switching a physical path using Fill in the blank 2 of 15  or fibre optic cables is setup between the sender and receiver prior to Fill in the blank 3 of 15  of the message.  The path remains open throughout the communication and is only released for use by others once the message is Fill in the blank 4 of 15 .  Although circuit switching is still used, it isn’t the best choice for large networks because it is difficult to Fill in the blank 5 of 15  up and every connection has to be capable of supporting the maximum Fill in the blank 6 of 15  that might be required.

For large networks, and the internet, packet switching is used instead.  Here the message is broken down into smaller parts (data Fill in the blank 7 of 15 ) which are sent individually through the network by the shortest\1}  route available.  The packets are given a ‘packet Fill in the blank 8 of 15 ‘ to identify the order they are in.  When the individual packets arrive at their destination they will be Fill in the blank 9 of 15  back into the correct order.  Once all of the packets have safely arrived a message will be sent to the original computer as confirmation. If a packet is missing or Fill in the blank 10 of 15  then the message will ask for that particular packet to be resent.

The data packets contain three important pieces of information:

1. a Fill in the blank 11 of 15 or return address to say where the packet originated from
2. a Fill in the blank 12 of 15 address to tell the packet where it has to go
3. a Fill in the blank 13 of 15 number so that the individual data packets can be reassembled in the correct order once they have all safely arrived at their destination

Benefits of packet switching include:

1. Robustness – there are many paths through which the packets can travel.
2. The connection is required for only a brief period of time, unlike circuit switching where it is held until the whole message is transmitted.
3. If a packet is lost or corrupted only that packet needs to be resent – unlike circuit switching where the whole message has to be resent.
4. Each packet carries its own Fill in the blank 14 of 15 correction codes, so if a few bits are corrupted, they can often be corrected.

However, one issue is that when one packet arrives more slowly than the others, it is missing or corrupted then delays can occur (known as Fill in the blank 15 of 15 ).

The speed, or bandwidth of a network, is measured in Fill in the blank 1 of 7 per second.  The more bits per second, the more Fill in the blank 2 of 7 that can be transmitted in a given period of time.   Most people have to share the bandwidth on a network and as there is a limited bandwidth available, the more people that are using the network, the slower it can become.  The term, ‘Fill in the blank 3 of 7 ratio’ is the ratio or number of users compared to the bandwidth available.

Networks often use physical connections to join them together.  The most common choice is using Fill in the blank 4 of 7 cables or Ethernet cables which carry electrical signals.  These can be either Cat-5 or Cat-6.  Cat-5 cable is the least expensive and is fine for a network which is around 100Mbps.  However, if the network needs to be around 1 Gbps or above then Cat-6 is the better option.

Even faster than Ethernet cables are Fill in the blank 5 of 7 optic cables.  These work by transferring data using Fill in the blank 6 of 7 which is reflected along the inside of the cable.  They offer very high bandwidth but are expensive when compare to Fill in the blank 7 of 7 cables.