1.5 Network topologies, protocols and layers

Bill needs to send a document across a network to Ben. Write an algorithm to show how packets are used to send the document, starting from when Bill clicks send (sending), and finishing when Ben reads the document (receiving).

Which algorithm best represents sending a packet?

• Bill's computer splits data into equal sizes packets (1)

  Each packet is given the address of Ben's computer (1)

  Each packet is given a number (1)

  Each packet is given error checking data (1)

  The packets are sent across the network (1)

• Ben's computer checks if all packets have been received? (1)

  If No...

  ...Check again (1)

  ...Increment timer (1)

  ...If timer > max wait (1)

  ...Send timeout to Bill's computer (1)

  If Yes...

  ...Reorder packets based on their number (1)

  ...Display the document (1)

  ...Send receipt confirmation (1)

  ...Each packet is checked for errors

  (1)...

  ... if corrupt a message is sent back to sender (1)

• Bill's computer splits data into different sizes packets (1)

  Each packet is given the address of Ben's computer (1)

  Each packet is given a with a zero (1)

  Each packet is given erroneous data data (1)

  The packets are sent across the network (1)

• Ben's computer checks if all packets have been received? (1)

  If Yes...

  ...Check again (1)

  ...Increment timer (1)

  ...If timer > max wait (1)

  ...Send timeout to Bill's computer (1)

  If No...

  ...Reorder packets based on their number (1)

  ...Display the document (1)

  ...Send receipt confirmation (1)

  ...Each packet is checked for errors

  (1)...

  ... if corrupt a message is sent back to sender (1)

Bill needs to send a document across a network to Ben. Write an algorithm to show how packets are used to send the document, starting from when Bill clicks send (sending), and finishing when Ben reads the document (receiving).

Which algorithm best represents receiving a packet?

• Bill's computer splits data into equal sizes packets (1)

  Each packet is given the address of Ben's computer (1)

  Each packet is given a number (1)

  Each packet is given error checking data (1)

  The packets are sent across the network (1)

• Ben's computer checks if all packets have been received? (1)

  If No...

  ...Check again (1)

  ...Increment timer (1)

  ...If timer > max wait (1)

  ...Send timeout to Bill's computer (1)

  If Yes...

  ...Reorder packets based on their number (1)

  ...Display the document (1)

  ...Send receipt confirmation (1)

  ...Each packet is checked for errors

  (1)...

  ... if corrupt a message is sent back to sender (1)

• Bill's computer splits data into different sizes packets (1)

  Each packet is given the address of Ben's computer (1)

  Each packet is given a with a zero (1)

  Each packet is given erroneous data data (1)

  The packets are sent across the network (1)

• Ben's computer checks if all packets have been received? (1)

  If Yes...

  ...Check again (1)

  ...Increment timer (1)

  ...If timer > max wait (1)

  ...Send timeout to Bill's computer (1)

  If No...

  ...Reorder packets based on their number (1)

  ...Display the document (1)

  ...Send receipt confirmation (1)

  ...Each packet is checked for errors

  (1)...

  ... if corrupt a message is sent back to sender (1)

The owners of a large bakery have a Local Area Network (LAN) with a star topology. They order their supplies over the Internet. When data is transmitted from the bakery to the supplier, network protocols are used.

Define what is meant by a 'network protocol'.

• A network protocol defines rules for data transmission

• A network protocol is the radio waves used for data transmission.

• A network protocol is the physical cables used for data transmission

TCP/IP is a set of protocols based on layers.With regards to network protocols, define what is meant by a 'layer'.

• A division of network functionality

• The hierarchy of network cables and their associated speeds

• Packets being sent in layers.

TCP/IP is a set of protocols based on layers.Describe one advantage of using layers to construct network protocols.

Answers: 2

• It is self-contained (1)......it allows different developers to concentrate on one aspect of the network (1)

• A layer can be taken out and edited without affecting other layers (1)......it promotes interoperability between vendors and systems (1)

• They are intertwined(1)....it requires developers to understand all layers. (1)

The owners of a large bakery have a Local Area Network (LAN) with a star topology. They order their supplies over the Internet. When data is transmitted from the bakery to the supplier, network protocols are used.

The owners of a large bakery have a Local Area Network (LAN) with a star topology.

Explain three reasons why the bakery may use a star network topology for their LAN.

Answers: 3

• It is easy to add a new node or device

• Management of the network can be done centrally

• If a node or device fails it does not affect the rest of the network

• Management of the network is done at each node in the network

• Multiple routes for data to travel if one device fails.

A bank uses a local area network to connect all the computers in its head office.Computers in the network can be identified using both IP addresses and MAC addresses.

Describe the difference between IP addresses and MAC addresses.

• - IP addresses can be changed / are allocated as needed

  - MAC addresses can't be changed / every device has a fixed MC address

• - IP(v4) addresses are 4 bytes long

  - MAC addresses are 6 bytes long

• - IP(v4) addresses are normally written in denary

  - MAC addresses are normally written in Hex

• -IP addresses are configured by software

  - MAC addresses are configured in hardware

• -IP addresses are used for routing across a WAN / internet

  -MAC addresses are only used within the LAN

Which best defines a star network?

• Each device is connected by an individual cable directly to the server. These are usually the layout of choice in schools and offices because they tend to be the most reliable of the topologies.

• Where some or all of the workstations or other devices are connected directly to each of other. Most are usually connected to the node that they exchange the most data with.

Which best defines a mesh network?

• Each device is connected by an individual cable directly to the server. These are usually the layout of choice in schools and offices because they tend to be the most reliable of the topologies.

• Where some or all of the workstations or other devices are connected directly to each of other. Most are usually connected to the node that they exchange the most data with.

What is an advantage of Wifi over Ethernet?

Answers: 3

• Cheap set up costs

• More exensive

• Can connect multiple devices without the need for extra hardware

• Less disruption to building due to no wires being installed

• Faster transfer speeds