Computer Science Comp 01 1.3 Networks - OCR GCSE

Define a WAN

Any network computers communicate with using 3^rd party carrier

Explain Packet switching (9)

File is split into packets

Packets flow through internet – taking different routes

The packet will have senders and receivers IP addresses, total number of packets, packet number and error checking data

Data is then reassembled and missing packets resent

What is the DNS + how does it work?

Translates web address to IP address

Request goes to server + if not in database passes the request down the hierarchy

What are IP addresses?

The number assigned to your specific geographical location - Can change

Describe the role of a NIC

Built into every networked device

Allows devices to connect with each other

What are MAC addresses + what do they do?

Assigned to each NIC + cannot ever change

When you request a page, each router the data passes through uses the MAC address to send the data packet to the correct destination.

Define LAN

Local area network

Operates on single site with individual cabling systems

Star network – define, adv. + disadv.

All devices in network are connected to central switch/hub.
Advantages	Disadvantages
If 1 cable fails only 1 node is effected	Need additional hardware
Fast data transfer	If central hub fails then network fails

Mesh network definition

Nodes act as routers to send data to destination. Can be wired/wireless, full/partial

Mesh advantages and disadvantages

Advantages	Disadvantages
No single point of failure	Can have redundant connections
Can make changes to network easily	Wired cable expensive

Define Switch

Connects nodes together

Know MAC addresses and send data packets to correct computers when they arrive

Define Router

Looks at destination on packet + sends to network that is closer

What is Transmission media?

The way data is communicated through a network. E.g. fibre optic, ethernet, wireless and copper.

What are WAP’s and what do they do?

A device that allows nodes to connect to a network without using cabling

Usually connects to router via wired network

What are the different frequency standards with advantages and disadvantages?

	Advantages	Disadvantages
2.4Ghz	Bigger range	More interference
5Ghz	Less crowded	Lower range

what is encryption and why do we use it?

Encoding data to make it harder to understand

Intercepted data can be read and understood if it is transferred over a network

Define private vs public encryption keys

Private – 1 key to encrypt + decrypt – must be given to recipient to decrypt

Public – 2 keys are used – more secure as never have to reveal decryption key

4 wireless encryption standards?

WEP, WPA, WPA2, WPS

What is the client server network model?

Server is powerful computer which provides services/ resources for client. Server waits for request, processes request and gives data back to client.

Peer to peer network

No hierarchy or central server to control files

Suitable for small LAN’s with less nodes

Easy to see files on and communicate with other computers

Advantages and disadvantages of a peer to peer network

Easy to set up since no additional hardware needed Can share hardware + communicate directly with each other

Easier for viruses to be spread Have to back up individually Can’t get data from other computers if off

Cloud Computing  advantages and disadvantages

Can access data anywhere and whenever Don’t need powerful computer – data backed up by service provider

Personal data stored on company servers Service unusable without internet connection

Copper cables vs fibre optics vs wireless connection

	Good	Bad
Copper	Cheap + reliable	Low bandwidth, heavy
Fibre Optics	Fast, good range, little power needed, more secure	Expensive to set up + hardware
Wireless	No cables, easier to add devices	Less secure, more interference

What is bandwidth?

How much data can be carried through a connection at any given time

What is latency?

The length of time taken for a packet to travel through a network

Define protocol

A set of rules

HTTP(S)

On application layer. Used to access web pages via internet. S is needed if any personal information could be stored on website. Protocol requests web page from web server

FTP

Used for sending and receiving files

POP + IMAP

Protocols used to receive email

POP – deletes email from server after retrieved

IMAP – emails stored on servers

how does SMTP work

Email software sends email to SMTP server used. Mail server transports message through mail relays. Arrives at mail server closest to destination

TCP/IP

TCP – packet switching

IP – routes packets from 1 IP address to another

What are the different layers?

application, transport, internet, link

Why use layers?

Each layer is independent

Can change layers without affecting others

Separates tasks – can focus on 1 layer at a time

Groups together similar protocols

What is the cloud

services and file storage that can be accessed via the internet