IB Computer Science HL Paper 1 Topic 3

Network

* A group of computers and other computing hardware devices linked together through communication channels to enable communication between users

Bus topology

Computer network in which a bus (cable) connects all devices together through a common cable

Check digit

Extra digit added to numerical data that is used to check data integrity after input, transmission, storage and processing

Data packet

• Portion of a message that is transmitted through a network

• Contains data such as check digits and destination address

Handshaking

Exchange of predetermined signals to signify that a connection has been established between two systems

Protocol

* International rules that ensure the safe transfer of data between systems

Hub

• Network connection point for devices

• Data arriving at a hub is copied and sent to all the devices on the network

What does TCP / IP stand for?

Transmission Control Protocol / Internet Protocol

TCP / IP

* Standard communications protocol used to connect hosts on the Internet

Server

• A computer system that serves as a central repository of data and programs and is shared by clients

• Role is to await and fulfill requests from client programs

Client

* A piece of computer hardware or software that accesses a service made available by a server

Network Types

• Local Area Network (LAN)

• Wireless Local Area Network (WLAN)

• Virtual Local Area Network (VLAN)

• Wide Area Network (WAN)

• Storage Area Network (SAN)

• Internet

• Extranet

• Virtual Private Network (VPN)

• Personal Area Network (PAN)

• Peer-To-Peer (P2P)

Local Area Network (LAN)

• Computer network where all the connected computers are within a limited geographical area (e.g school, office, home)

• Connection may be through cables and / or microwave transmission

Virtual Local Area Network (VLAN)

• A logical group of network devices that appear to be on the same LAN despite their geographical distribution

• Allows a group of network devices to communicate in a simulated environment as if they exist in a single LAN

Pros of VLAN

• Scalability

• Security

• Ease of network management

• Can quickly adapt to changes in network requirements and relocation of workstations and server nodes

Wireless Local Area Network (WLAN)

• A wireless distribution method for two or more devices that use high-frequency radio waves, and often includes an Internet access point

• Allows users to move around the coverage area while maintaining an Internet connection

Wide Area Network (WAN)

• Computer network where all the connected computers are in a larger geographic are than served by a LAN or MAN (metropolitan area network)

• Internet is a WAN

Peer-To-Peer (P2P)

• A network model in which some computers or hardware devices exchange files (e.g. BitTorrent)

• No central server - equal client system

• Supports file sharing or collaborative work

Virtual Private Network (VPN)

• Uses the Internet to allow people to access the network remotely

• Provides a secure connection by encrypting the network (IPSEC protocol) - of hacked data will not be understood

• Uses tunneling protocols - allows the data to be hidden while travelling across the Internet

Extranet

• A controlled private network

• Allows people to gain information about a specific company without granting access to the entire network

• The specific LAN or WAN is the extranet, and can only be accessed by people with the required credentials e.g usernames / passwords

Personal Area Network (PAN)

• A network that interconnects devices centred around an individuals workspace - a LAN that only supports one person

• Covers a very short range

Pros and cons of wireless networks

Proa

• Ease of use for mobile users, as they can work in many different locations

• Less time, space and cost due to lack of need for cables

Cons

• Security issues, as wireless transmissions are easily intercepted

Voice Over IP (VoIP)

• Audio and video stream transmitted over the Internet, broadband internet connection needed

• Can be integrated in an office desk computer

Layers in the seven layer Open Systems Interconnection (OSI) model

• Application

• Presentation

• Session

• Transport

• Network

• Data Link

• Physical

Advantages of using layers in communication

• Easy to manage

• Greater understanding of each layer

• Common language for each layer

• Makes protocol design easier

Layers in TCP / IP protocol model

• Network access

• Internet

• Transport

• Application

Benefits that protocols provide

• Data integrity - information has not been changed / corrupted

• Source integrity - identity of the sender is validated

• Error checking / correction

Bandwidth

• The theoretical speed of data in a medium

• Depends on the signalling technique used and the physical properties of the medium

Throughput

• The actual transfer rate of data

• Affected by:

  • Bandwidth of the network

  • Distance

  • Amount of users