OCR Computer Science AS Level - 1.3.2 Networks

Flashcards for OCR Computer Science AS Level - 1.3.2 Networks

What is a network?

Two or more computers connected together that transmit data

What are protocols?

Sets of rules defining how two devices communicate with each other

Why are protocols standard?

Protocols are standard so devices from different manufacturers don't have problems communicating

Describe the structure of the Internet

The Internet is a global network of interconnected networks

What does TCP stand for?

Transmission Control Protocol

What does IP stand for?

Internet Protocol

What is the function of the application layer during data transmission?

This layer specifies what protocols need to be used to relate the application to what it’s being used for. (e.g HTTPS for a web page FTP for files or SMTP/POP3/IMAP for emails)

What is the role of the transport layer during data transmission?

Establishes an end-to-end connection between the source and recipient computers. It also splits up the data into packets.

What is the role of the network/internet layer during data transmission?

Adds the source and destination IP address.

What does the application layer do when it receives data?

Presents data in the form it was sent

What does the transport layer do when it receives the data?

Removes the port number and reassembles the packets.

What does the network/internet layer do when it receives the data?

Removes the IP address

What does the link layer do when it receives the Data?

Removes the MAC addresses

What is a Local Area Network?

A network spread over a small geographical area/ positioned on a single site

What is a Wide Area Network?

A network spread over a large geographical area, usually requiring extra hardware which is usually owned by telecommunications companies. Routers direct data packets on WANS

What does DNS stand for?

Domain Name System

What is DNS?

The name given to the method of naming internet resources. (.com, .uk etc)

What is circuit switching?

The process of creating a direct link between two devices and transferring data the entire duration of the link.

What is a requirement of Circuit Switching?

The transfer and download rates must be identical on both devices.

What is packet switching?

A method of communicating packets of data across a network

Give an advantage of packet switching

Multiple methods to ensure data arrives correctly, Multiple methods to arrive to destination, if one breaks you can always go through another route. Transfer packets over a very large network

Give a disadvantage of packet switching

Time is spent deconstructing and reconstructing the packets

Give an advantage of circuit switching

Data arrives in logical order which results in a quicker reconstruction of data, Enables two users to hold a call without any delay in speech.

Give two disadvantages of circuit switching

Bandwidth is wasted during periods when no data is sent, which means this process isn’t scalable. Devices must transfer and download at the same rate. All data is vulnerable to interception. This process can’t react to faults in the network

What does the header of a data packet contain?

The sender and recipient IP addresses, Protocols being used, Order of the packets, The time to live / hop limit

What does the packet payload contain?

The raw data

What does the packet trailer contain?

The checksum or cyclic redundancy check

What is client-server networking?

A relationship between terminals (computers) and a single server which allows them to communicate, and share resources.

Give an advantage of client-server networking

Increased security, Central single backups, Data and resources can be shared

Name a disadvantage of client-server networking

Expensive to set up, Trained staff are required to maintain the network

What is peer-to-peer Networking?

A network where the terminals are all connected to each other to share resources.

Give two advantages of peer-to-peer networks

Cheaper to set up, Easy to share resources, Easy to maintain

Give two disadvantages of peer-to-peer networks

Peer-to-Peer networks can be used to contribute towards piracy, Each computer has to be backed up independently