IB Comp Sci - Topic 3

Server

A computer that provides client stations with access to files and printers as shared resources to a computer network

Client

A computer that requests data stored on a server.

Hub

the connection point for devices on a single network. network devices and computer systems connect to a hub using Ethernet cables that attach to a port.

Switch

the connection point for multiple devices on a single network. unlike a hub, the switch can identify which network device is connected to which port.

Router

a more sophisticated device than both a hub and a switch. its use is to join multiple networks and serve as an intermediary between these networks so that data can be exchanged effectively.

LAN

Local Area Network. A small group of computers connected, usually over a very small area. Copper cables. high data transfer rates

MAN

Metropolitan Area Network. Networks over a larger area, city-size, connecting computers and LANs. Sometimes with fibre optics.

WAN

Wide Area Network. Network over large geographical areas, often across continents. Most common WAN is the internet. Connects to many computers.

VLAN

Virtual Local Area Network. Computers behave as if in LAN but in reality they are far apart in different network, where they tunnel into a virtual LAN. Done when playing online computer games.

WLAN

Wireless LAN, just with radio wave connections instead of wires. Slower than LAN.

GAN

Global Area Network. The nodes are spread out globally.

WPAN

Wireless Personal Area Network. (Bluetooth). Consists of computers, phones, tablets, etc.

Extranet

Your home computer can access your work network. Can be considered a restricted internet in a certain environment.

Intranet

In a school. We can see out to internet, but internet cannot see in. (Like one way mirror)

Internet

The name for world wide web.

P2P

Peer to peer. All computer systems in the network are decentralized and are both clients and servers at the same time, consuming and supplying resources from and to the other computer systems on the network.

SAN

Storage Area Network. Network which provides dedicated access to storage. (own storage device, not wider network) appears as a device to OS.

LAN vs WLAN Similarities

Both act on a local level. Both allow communication. Both used to connect devices. Both allow sharing of resources.

LAN vs WLAN Differences

They use different transmission medium. LAN is safer. LAN is faster. WLANs offer greater flexibility.

LAN vs VLAN Similarities

Both act on a local level. Both have same attributes. Both allow communication. Both used to connect devices. Both allow sharing of resources.

LAN vs VLAN Differences

VLAN delivers better performance. VLAN is safer. Formation of virtual workgroups is easy. VLANs offer greater flexibility. VLANs are independent on the medium and the physical topology. Sometimes the management/administration of a VLAN is complex.

Standards

Common rules providing "international language" enables compatibility for all computer systems around the world

OSI Model

Open system interconnection model defines a networking framework to implement protocols in seven layers. (to communicate)

Physical (Layer One)

Provides mechanic, electric and functional help to activate and deactivate physical connections. How a bit is transferred across a medium, transmits as 0s and 1s.

Data Link (Layer Two)

Ensure faultless transmission of data. Error handling of physical transmission. Amends transmission rates according to buffer of receiver.

Network (Layer Three)

Handles routing of packets across a network through devices to reach destination.

Transport (Layer Four)

End to end connections. Definition of data segments - assignment of numbers - data transfer - reassemble of data at the destination.

Session (Layer Five)

Manages sessions between two users.

Presentation (Layer Six)

Provides data format information, data compression information and data encryption information to the application.

Application (Layer Seven)

Performs various services for the applications used by the end users.

Please Do Not Teach Students Pointless Acronyms

Physical, Data (Link), Network, Transport, Session, Presentation, Application

TCP/IP Model

Describes all the functions that take place at each layer of protocols within the TCP/IP suite. Hierarchical model protocol that models and represents all the functionality required for successful communication between users.

OSI and TCP/IP

The OSI Model and the TCP/IP Model are two separate network protocol models. They can be used separately or together.

VPN

A virtual private network makes a "tunnelled" connection through the Internet or any other public network.

Hardware and Software of VPN

Internet Access, VPN Software, VPN Routers, VPN Appliances, VPN Concentrators.

Secure VPN

All traffic must be encrypted, authenticated and then sent along virtual tunnels.

Internet protocol security protocol (IPsec)

Secure transmission over public IPs. Standard encryption algorithm provide confidentiality Authentication via digital certificates.

Secure Socket Layer or Transport Layer Security

Doesn't need special client software. All web servers and browsers support this method of providing a VPN.

Remote access VPN

Connects individual hosts to private networks and facilitate teleworkers who need to access their company's network securely using the Internet.

Use of a VPN

VPNs gave rise to home offices as it allowed workers to connect to a company's internal network. For example, a mother can work from home that their own speed in time to pick her kids up from school.

Benefits of a VPN

Communication is easier, companies take advantage to provide secure connections, improves overall productivity, offers flexibility to remote offices.

Protocol

a set of rules that defines the rule and conventions for communication between network devices.

Data packet

A unit of data in a form suittransfer between computers that communicate on a network.

Source integrity

Identity of sender has been validated. digital signatures verify identity.

Data integrity

Information has not been changed/corrupted deliberately or accidentally during transmission. Checked using things like checksums.

Flow control

Network infrastructures have limited memory and bandwidth. Transport layer takes advantage of protocols where overload of resources occurs. It slows down transfer rates.

Congestion management

Request on network resources exceeds capacity.

Deadlock prevention

Two or more networks competing action are each waiting for the other to finish and as such they are stuck doing nothing.

Why protocols are necessary

Without protocols, no information can be transmitted as computers do not know how to interpret the signals coming through the network.

Bandwidth

theoretical speed of data

Bottleneck

affects throughput as a smaller segment in the communication compared to a larger segment next to it slows down the bandwidth, like the shape of a bottleneck.

Why speed can be affected

Many users, interference can corrupt many data packages, causing retransmission.

Lossy

Some loss of information is acceptable and there is no way to get the original file back.

Lossless

this compression method reduces the number of bits by first identifying and then eliminating any statistical redundancy.

Why compression is necessary

Compressing data for faster transmission used to be essential. Transmission speeds have improved, but we are transmitting more, so compression is required to transmit the vast amounts of data without using up all the bandwidth.

Metal conductors

• Cheap

• Average to high speed

• High reliability

• Relatively secure

Fibre optics

• Expensive

• Very high speed

• High reliability

• Relatively secure

Wireless

• Price varying by size of network (WLAN is usually very cheap)

• Middle speed

• Average reliability

• Insecure

Copper

Most common cable

Coaxial

Two copper conductors. used in computers and TV

Unshielded Twisted Pair (UTP)

Popular in LANS. good for short distances.

Shielded Twisted Pair (STP)

More difficult to install that unshielded.

Fibre Optic Cable

Carries beams of light through glass. Used in data transmission and telephone lines.

Microwave Radio

Mobile telephone networks and LANs. Information is carried through the air. High bandwidth, but lower than cables. Weather can effect the performance.

Infrared

Short distances. Cannot pass through objects. Line of sight is required.

Bluetooth

Microwaves to exchange data. Very low power levels. Personal Area Network

Datagram Packet Switching

Each packet contains receiver address.
The path between the source and the destination can be different.

Virtual Circuit Packet Switching

With this method, a route from source to destination is set up before any transmission takes place.

Datagram Packet Switching advantages

Single packets are small, waiting times are low. Resource will be given fairly to participants in the network. Small packets allow for faster error detection. High resistance against fallout. As route not assigned network utilised better.

Datagram Packet Switching disadvantages

Overloading can occur at transmitting station
because transport routes aren't fixed.
Packets do not arrive in order.
All participants have to use the same network protocols. No constant bandwidth is guaranteed and big fluctuations in bandwidth can happen.

Point to point

Simplest definition. Permanent link between two endpoints.

Bus

All of the various devices in the network are connected to a single cable or line.

Star

Each individual piece of a network is attached to a central node.

Ring

Each node connects to exactly two other nodes, forming a single continuous pathway through each node.

Mesh

the infrastructure nodes connect directly, dynamically and non hierarchically to as many nodes as possible and cooperate with one another to efficiently route data from/to clients.

Tree

A multipoint electrical circuit with multiple branches of the trunk of the central, or root, or bus.

Fully connected

A fully connected network is which there is a direct link between all pairs of nodes.

Hybrid

Integration of two or more different topologies to form a resultant topology.

Advantages of wireless networks

• Easy to set up

• Can be installed

• Allows mobility

• Easy to add new participants

Disadvantages of wireless networks

• Traffic through network can be intercepted by unauthorized people

• Slow transmission speeds

• Interference from other wireless stations, cables etc.

• Signal range depends on participating devices' antenna

• Many different standards may not compatible with each other.

Concerns with wireless networks

There is a change in working patterns. Physical and internet communication has become simultaneous. 26% of car crashes are phone related.

Modem/router

Connects you to the internet

Device

A device like a laptop is required to connect to the internet.

NIC Card

Required for the device where you can plug in Ethernet cables for example.

Antenna

Routers utilize antennas that significantly increase the effective communication area of the wireless network.

Repeater

Connects to router. Receives an existing signal from a wireless router or access point and rebroadcasts it.

Ethernet to Wireless Access Point or Repeater

Uses Ethernet cables to carry the signal to the wireless repeater or WAP.

DHCP

Dynamic Host Configuration Protocol. Allows server to automatically assign an IP address to a client device. The alternative is to have a static IP that stays the same every time you log onto the internet.

Firewall

Determines what data comes in and goes out of a network or PC.

SSID

Service set identification. 32 alphanumeric characters. It is used to differentiate on WLAN from another.

NIC Drivers

A device driver for the NIC card. Operates or controls the hardware of the card. Acts as a translator between the wireless card and the applications or OS of the device.

NOS

The network operating system handles system resources and is responsible for managing all the protocols, hardware and applications that have to cooperate in order that a network can exist and function correctly.

Security Software

Includes all software that prevents unauthorized access use, disruption, modification, just to name a few. By using intrusion detection systems, intrusion prevention system (IPS), etc.

WAP

Wireless Application Protocol specifies a set of protocols for accessing information over a mobile wireless network.

Web Browsers

Application software that is used to find retrieve and display content on the WWW, including web pages, text images, audio and videos and other content.

Encryption

Necessary to protect data from unauthorised access during internet use or any untrusted network.

Symmetric KEncryption

Same key is used for encryption and decryption. Each device has a secret code that is used to encrypt a packet before it is sent over an untrusted network.

Data Encryption Standard (DES)

56- bit key.

Advanced Encryption Standard (AES)

128 to 256 bit keys offering a much greater number of possible combinations.

Asymmetric key encryption

Uses a public key for encryption and a private key for decryption. Keys are mathematically linked. TLS and SSL encryption protocols.