Network topology

A local area network is a small interconnected area. It typically consists of several clients, a server and a router.

A router, which can be software or hardware, does the following:

• Processes packets by seeing where to send them from their headers.
• Acts as a bridge between the LAN and the internet.
• Acts as a modem, which translates digital signals (0s and 1s) to analog signals.
• Can have a firewall to block specific ports.
• Provides a WAP.

A wireless access point provides a ‘Wi-Fi’ signal which is done over radio. There are several protocols that they can use, such as WPA and WEP, which have various advantages and disadvantages.

A switch is used to connect two devices in a network.

A wide area network is spread over a wide area. The world-wide web is by far the most used WAN.

A media access code is the unique physical address of a machine connected to a network.

A network interface card is what a computer uses to connect to a network - the type of this dictates the speed of transmission. This will have a unique MAC address.

A topology is a logical network layout, where the network can be LAN or WAN. There are several kind of topologies.

Bus topology

A bus topology is one where a backbone cable connects all the devices and has terminators to absorb reflected signals. Coaxial cables are used for the backbone and to connect computers to the backbone. Data is transmitted along the backbone to every single workstation but only the workstation whose MAC address it is intended for will accept and process this message. Therefore, each station has equal transmission priority.

They use a CSMA / CD protocol to avoid and manage data collisions - devices transmitting at the same time are forced to pause for a random amount of time before trying to transmit data again.

Advantages:

• Installation is cheap.
• Easy to add devices.
• Less cabling needed.
• Works well for small networks.

Disadvantages:

• Depends on the backbone.
• There’s a limit on how many devices can connect.
• Problems are hard to isolate.
• Response rate can be slowed because of shared cable.

Physical star topology

A physical star topology is one that is connected by Ethernet cables. A hub broadcasts to every connected workstation whereas a switch broadcasts only to the relevant workstation. Advantages:

• One cable going down does not bring down the whole network.
• Tracking down device and cable problems is easy.
• Can be upgraded to higher speeds.
• Has lots of support as it is the most popular.
• Hubs provide a centralised management.

Disadvantages:

• Required more cabling than bus networks.
• If the central hub fails, the whole network goes down.
• Costs are higher than most bus networks.
• More expensive to maintain as specialist knowledge is needed.

Types of networking

Peer-to-peer networking

Peer-to-peer networking is when devices communicate directly to each other without any in-between devices, as a result devices are self-organising and distribute control. However, it is vulnerable to the following:

• A Distributed Denial of Service attack.
• The network being poisoned / given bogus data.
• Your IP address could be leaked and lots of things can happen as a result. If P2P file sharing is taking place, your password can be brute forced and files found.
• Unfairness in sharing.
• This can be outright blocked.

Client-server networking

Client-server networking is when devices fall into one of these categories:

• Servers provide services to clients, such as web services and e-mail.
• Clients use services provided by servers, such as in a web browser, and an e-mail client.