Computer Science Ch.21 Networks + Network hardware (Ch.23)

network

an arrangement of computers and other devices connected together to share resources and data

network service

an app running on a server which provides facilities or operations such as data storage, printing or communications

LAN

a network that covers a relatively small geographical area, often a single site

WLAN

a local area network in which connected devices use high-frequency radio waves to communicate

PAN

network used for data transmission over short distances by computer devices, such as laptops, mobile phones, tablets, media players, speakers and printers

Bluetooth

a protocol for the short-range wireless interconnection of electronic devices

WAN

a network that covers a large geographical area. It connects together two or more LANs and is usually under shared ownership

largest WAN / mesh network

the Internet

client-to-server network

a network that has atleast one server to provide services to the client computers

3 step process of a client accessing files from the sever

1) A client makes a connection using its address.
2) The client makes a service request to the server.
3) If the request is valid, the server sends the requested data to the client using the address.

peer-to-peer network

a network that doesn’t have any dedicated servers. Each computer in the network can act as client and server

network topology

describes how devices on a network are connected together

Advantages of networks (3 points)

Devices can share resources, Files can be accessed through any computer in the network, Data is easy to backup as it is stored centrally in the server

Disadvantages of networks (3 points)

Purchasing network hardware is expensive, managing large networks are complicated, viruses may infiltrate the network and infect every computer

Network Interface Card (NIC)

A small piece of hardware in a device that provides the capability to connect to wireless networks.

Wireless Acess Point (WAP)

a device that is used to connect one or more computers wirelessly to an existing physical wired network

Router

Connect one network to another such as your home’s LAN to the Internet.

Switch

Connect wired devices to a network and know the MAC address of each computer and route data to each computer specifically.

Hub

Connect wired devices to a network but send all the data to all the computers whether they want it or not.

Bridge

Connect LANs together to create a WAN

Bus Topology

Each node is connected to a single cable, and data can be sent in both directions. Terminators are placed at the end of each side of the cable to absorb signals that have reached the end. Data is sent to all nodes but is only accepted by the node that requires it.

Advantages of Bus Topology (2 points)

1. Relatively cheap to install since only one cable is needed

2. Easy to add extra nodes

Disadvantages of Bus Topology (4 points)

1. Whole network fails if cable is damaged

2. difficult to identify fault on cable

3. More nodes cause network to operate slower because more collisions happen

4. All data sent is received by all devices so there is a security risk

Ring Topology

Each node is connected in a closed loop in the shape of a ring. The data continues along the ring in the same direction until it reaches its destination.

Advantages of Ring Topology (2 points)

1. Adding extra devices does not affect performance

2. easy to add network devices

Disadvantages of ring topology (4 points)

1. Whole network fails if a cable is damaged or a device fails

2. Removing or adding device shuts down network temporarily

3. Difficult to identify fault on network

4. More expensive to install than bus topology since more cable is used

Star Topology

Has one central point with all other nodes connected to it, which is either a hub or a switch which directs and receives messages to the correct recipients.

Advantages of star topology (4 points)

1. Damaged cable does not stop entire network from working

2. If switch is used only required nodes receive message

3. Easy to locate faults because usually one device is involved

4. New device can be added or removed without closing the network

Disadvantages of star topology (2 points)

1. If the hub or switch fails the whole network will fail

2. Expensive to install because of the amount of cable needed and the hub/switch

Mesh Topology

Each node is connected to atleast one other node, and it is more common for them to be connected to more than one node. The most efficient route is typically calculated before data is sent thorugh it.

Adantages of mesh network (3 points)

1. Very fault tolerant - If one device fails messages can be rerouted around it

2. Very high performance because each device is likely connected to multiple other devices

3. In a wireless mesh network each node extends the range of the network

Disadvantages of mesh networks (2 points)

1. Difficult and expensive to install wired mesh networks

   1. Diffiuclt to manage due to the number of connections within the network

Internet

a worldwide system of interconnected networks that enables information to be exchange and shared

communication media

the means by which data is transmitted between devices on a network (optic fibre, microwaves, e.t.c.)

range

How far data can be sent

protocol

a set of rules that govern how communications on a network should be formatted and what data they should include

eavesdrop

having unauthorized sight of data being sent from one computer to another over a network

Advantages of wired connectivity (3 points)

Faster (less latency, higher bandwith, larger range), Not easy to intercept or eavesdrop, less susceptible to interference

Disadvantages of wired connectivity (2 points)

Expensive to install and reconfigure, requires many cables

Advantages of wireless connectivity (5 points)

No need for cable to connect devices (less hardware, easy to connect), allows users to use their own device, wider range of devices can communicate because it does not depend on having the right cable, cheaper

Disadvantages of wireless connectivity ( 4 points )

Slower data transmission speeds, Interference from other wireless devices, Walls or physical objects can affect performance, Data must be encrypted to prevent eavesdropping or interception

latency

the delay encountered by data travelling through a network

SMTP Protocol (Simple Mail Transfer Protocol)

Used when sending emails through the internet from client to server and then server to server until it reaches its destination

POP3 Protocol

Used by clients to retrieve emails from a mail server (all emails are downloaded when there is a connection between the client and server)

IMAP

Messages can be read and stored on the message server so messages can be read from multiple devices rather than being downloaded into one

Ethernet

A family of protocols used in wired LANs

Wi-Fi

Protocol that sets out how data is transmitted on wireless LANs

TCP (Transmission Control Protocol)

Breaks up messages sent over the internet into small chunks called packets and reassembles the packets at the other end, using checksums to detect errors.

checksums

A technique that involves applying a mathematical formula to transmit a resulting number value with transmitted data, and then this formula is applied again in the receiving end to check for errors. If it does not match, the computer requests the data again

IP (Internet Protocol)

Routes individual packets from one IP address to another utilizing the router

Order of the TCP/IP protocol stack

Application, Transport, Internet, Link

Application layer

Interacts with user to provide access to services and data sent or received in a network

Transport layer

Manages end-to-end communication over a network

Internet layer

Deals with sending data across multiple networks from the source to the destination network

Link layer

Controls transmission and reception of data to/from a local network

packet

A small quantity of data being sent through a network which is labelled with the sender’s and recipent’s address and how many packets are being transmitted and the position of the current package in the complete message

web server

powerful computer system that stores web pages and any multimedia that the pages may contain

FTP (File Transfer Protocol)

Rules that must be followed when files are transferred between computers

HTTP (Hypertext Transfer Protocol)

The rules to be followed by a web server and a web browser when requesting and supplying information. Responsible for sending requests from web client to web server and returning web content from the server back to the client

HTTPS

allows for communication between host and client to be secure through encryption

Benefits of using networking layers (6 points)

Easy to understand, specialized for particular function, layers can be combined in different ways, layers can be developed or changed without affecting other layers, easy to identify and correct errors, provides universal standard for hardware and software manufactureres

About 2G

First to use digital communications, enabling text messages to me sent and introduced a multimedia messaging service

About 3G

Increased data transmission speeds to 2mbit/s, thus giving wireless access to the Internet enabling video calls, downloading, and streaming.

About 4G

Provided much higher speeds and rose the popularity of mobile gaming as it had much higher capacity thus facilitating many users at the same time, and had lower latency.

About 5G

Faster and more efficient than 5G, having much faster peak speeds and lower latencies supporting the IoT.