Unit 5: Networks and Web Technologies

A network is two or more computers connected together that can transmit data.

Physical topology is the ​physical layout​ of the network.

Logical topology is the​ way in which data flows​ around a network.

A network topology where all ​terminals ​(devices) are connected to a backbone cable

Cheaper to set up, doesn’t require any additional hardware.

• If the ​backbone cable fails​, the entire network gets disconnected. • As traffic increases, ​performance decreases. • All computers can ​see the data transmission (insecure).

A network topology which uses a central node (​switch/computer​) to direct the flow of data, MAC ​(Media Access Control) addresses identify each device.

• Performance is ​consistent​ even if network is being ​heavily used. • If one cable fails,​ only that station is affected. • It’s easy to add new stations.

• Expensive​ due to switch and cabling. • If the central ​switch fails,​ the rest of the network fails.

§A network topology where every node is connected to every other node. Most commonly found with wireless technology such as Wi-Fi.

• No cabling cost (wireless). • As nodes increase, the ​reliability and speed​ of network becomes better. • Fast​er since nodes don’t go through a central switch.

• You have to purchase devices with wireless capabilities. • Maintaining the network is ​difficult.

A protocol is a ​set of rules​ defining how two computers ​communicate​ with each other. Protocols are standard so that all devices have a designated method of communicating with each other, regardless of manufacturer.

• HTTP (Hypertext Transfer Protocol)​ • TCP/IP​ ​(Transmission Control Protocol / Internet Protocol) • POP (Post Office Protocol)​ and ​IMAP (Internet Message Access Protocol)​. • FTP (File Transfer Protocol)​

The Internet is a ​network of networks​ which allows computers on opposite sides of the globe to communicate with each other. Continents are connected to each other using ​large international backbone cables​. Many of these pass ​underwater​, linking continents to one another.

• Application Layer • Transport Layer • Network Layer • Link Layer

The application layer specifies ​what protocol​ needs to be used in order to ​relate the application that’s being sent​. For example, if the application is a browser then it would select a protocol such as HTTP, POP3, FTP, etc.

The transport layer uses TCP to establish an ​end-to-end connection between the source and recipient computer. The transport layer ​splits data up into packets​ and labels these packets with their packet number, the total number of packets the original data was split up into and the port number being used for communication. If any packets get lost, the transport layer ​requests retransmissions of these lost packets.

The network layer adds the source and destination ​IP addresses​. (The combination of the IP address and the port number is called a ​socket address​.) Routers​ operate on the network layer and use the IP addresses to forward the packets. The sockets are then used to specify which device the packets must be sent to and the application being used on that device.

The link layer is the ​connection between the network devices​, it adds the MAC address​ identifying the ​Network Interface Cards​ of the source and destination computers (or router if the device is on another network).

• A LAN is a local area network and a WAN is a wide area network. • A LAN is a network spread over a ​small geographical area​ while a WAN is typically spread over a ​large geographical area​. • A WAN usually requires extra ​telecommunication hardware​ owned by third-parties. • An example of a LAN would be the network in a home, school, or office. • An example of a WAN is the Internet.