networks

what is a network

two or more computers connected together with the ability to transmit data between each other

what is a protocol

a set of rules defining how two computers communicate with each other

why are protocols standard

so that all devices have a designated method of communicating with each other, regardless of manufacturer

application layer

specifies what protocol needs to be used on order to relate the application thats being sent

transport layer

uses TCP to establish and end to end connection between the source and recipient computer. this layer splits data up into packets and labels these packets with their packet number, total number of packets

network layer

adds source and destination IP addresses

link layer

the connection between the network devices, it adds the MAC addresses to identify the network interface cards of source & destination computers

DNS 4 marker

• user types in a URL and requests it from the browser

• the browser looks to the DNS server to give the corresponding IP address of the domain name

• the DNS resolver searches for the IP address by first looking at the TLD, and seeing if a server contains the corresponding IP address

• it works its way down the domain levels until it has found the server with the corresponding IP address.

• the browser now has the corresponding IP so it can present the web page to the user

what is payload

raw data to be transmitted

advantages of packet switching

multiple methods to ensure data arrives intact - checksums and cyclic redundancy checks

multiple routes can be used between devices

packets can be transferred over very large networks

disadvantages of packet switching

time is spent deconstructing the data packets

must wait for all packets to arrive before data can received

what is circuit switching

a method of communication where a direct link is created between two devices. This direct link is maintained for the duration of the entire conversation between devices.

requires two devices to transfer and receive data at the same rate

advantages of circuit switching

data arrives in a logical order which results in a quicker reconstruction of data

enables two users to hold a call without delay in speech

disadvantages of circuit switching

bandwidth is wasted during periods of time in which no data is being sent

devices must transfer and receive data at the same rate

using switches means electrical interference may be produced which can corrupt or destroy data

ties up sections of the network which cannot be used by others data until transmission has been completed

describe a client server network

consists of terminals knows as clients connected to a server (powerful central computer), that holds all important information and resources and has greater processing power than terminals

advantages and disadvantages of client-server

more secure as data is stored in one location

central backups are carried out so there is no need for individual backups

data and resources can be shared between clients

relatively expensive to set up

trained staff required to maintain server

if the server fails all terminals fail

describe peer to peer

a network in which computers are connected to each other so that they can share files. both computers can provide and request resources

advantages and disadvantages of peer to peer

• Cheaper to set up

• Allows users to share resources

• Easy to maintain

• Not dependent on a central server

• Specialist staff not required

• Impossible to trace origin of files

• Backups must be performed separately

• Poorer security

• May be difficult to locate resources