Mr C JohnstonICT Teacher

www.computechedu.co.uk

G055 - Lecture 03

Local and Wide Area Networks

Session Objectives

Understand the difference between Local Area Networks (LANs) and Wide Area Networks (WANs),

Know the different types of LANs and WANs that exist and be able to describe the characteristics of each including relevant advantages and disadvantages,

Be able to recommend a type of LAN or WAN for a given situation

Local Area Networks (LANs)

A Local Area Network (LAN) is a network of computers which is in one geographical location - one office, building or site,

Computers within a LAN are connected together with cables or wireless connections, A LAN will be made up of hardware linked together in a topology, LANs usually have fast data transfer speeds because they use their own cable / wireless

frequencies and don’t have to share with others, A LAN can be one whole network or spilt into logical segments known as virtual networks.

Wide Area Network (WAN) A Wide Area Network (WAN) are networks which covered a large geographical area – different sites in same town, different towns or even countries, Computers within a WAN are connected together using public telecommunications systems such as:

Public telephone system Public cable system Public wireless systems such as the mobile telephone network

Some WANs are connected with dedicated private leased lines although these are still part of the public telephone system,

Data transfers speeds may be iffy on a WAN as lines are being shared with others,

Often WANs are a network of LANs

Standard Cabled LANs A standard cabled LAN has all computers and resources connected to each other, Computers are connected together using cables, A device such as a switch or hub allows computers to communicate with each other, Provide fast data speeds and are reliable, When installing a cabled LAN need to be careful where cables are installed to avoid any accidents – normally truncking and sockets are used, Need to ensure have enough sockets for expansion to avoid having to re-cable rooms.

Wireless Local Area Networks (WLANs)

Each computer connected to the LAN has a radio receiver and transmitter (wireless network card) which sends and receives data signals to/from a wireless access point, All components in a wireless network can send and receive data using radio signals, Very useful in buildings where it would be difficult for cables to be installed or where staff are mobile using laptops and other portable devices, Installation is easier as not cables to install, Easy to add new computers and can be placed anywhere in building as long as they are in range, Slower than cable technology, Radio signals can suffer from interference – leads to slow and unreliability, Can pass though walls but may be picked up by outsiders unless properly secured which can be a security risk. Sometimes more expensive to install than wired networks – but price is falling

Virtual Local Area Networks (VLANs)

Large local area networks can become slow if all traffic has to go through the same central servers – so splitting it up into segments is useful, Each segment of the LAN has its own shape and connection type and although is separate there will be a link to the main LAN – and so each is called a virtual local area network or VLAN Most data is passed within machines on the VLAN and the VLAN will only receive data for computers within it rather than the whole network - so traffic is reduced The device with passes data between the VLAN and main LAN will pass across any data that needs to travel elsewhere, Network is faster in general if spilt up and suitable in large organisations – may have VLANs for each departments or security reasons If VLAN develops a fault this may go down but rest of network should remain operational, More difficult to add computers to a VLAN than LAN as each part of the wider LAN has to be told about it and which VLAN its part of.

Public Wide Area Networks (WANs)

The largest public WAN is the internet commonly defined as a network of networks, The internet is a world wide network of servers, clients and local area networks connected together to share

information, It is connected together using public telecommunication systems – these could vary in speed from location to

location Lines are usually shared in public WANs so there is always a risk that data packets could be intercepted, Not suitable for sharing secure data unless encryption techniques are used – bank transactions use public and

private key encryption.

Private Wide Area Networks (WANs)

More secure than using public telecommunication lines as you lease a dedicated private telephone line between different LANs and offices,

Probably quicker as have sole use Less chance of traffic being intercepted

Virtual Private Networks (VPNs)

A Virtual Private Network (VPN) is a way of connecting local area networks together securely without the cost of leasing a private line,

Using the internet alone is not secure - however it is possible to use it to establish a connection between LANs using a secure path,

The secure path is established with software which uses cryptographic tunnelling protocols that have measures to prevent interception, packet sniffing and identity spoofing – ensuring data only gets to the correct host,

A VPN therefore is a way of setting up a private WAN using an existing public network which most LANs are attached to in some shape or form.

Topic Exercise Download and complete this topics exercises

G055 Chapter p10-12

Common Answers