U3 - NETWORKS

Error Check Data Return Address Tracking Information Sequence No. Destination Address

Tells the receiving device what order the packet goes in

Allows the router to keep track of the data

Authenticates the data / Makes sure it hasn’t been corrupted

Contains the IP Address of the sending device in case an error occurs

Says where the packet needs to go

A network consists of two or more devices that are connected together allowing them to communicate and exchange information

Routers store all addresses of all the computers on a network. It can forward data to the correct destination.

Protocols are agreed formats that allow networks to communicate.

Handshaking - When two devices establish a connection How sending device indicates a message is over How receiving device will indicate a message has been received Agreement on data compressionmethod used

Physical layer Data link layer Network layer Transport layer Application Layer

Transmits raw data Consists of cables and switches Deals with all aspects of setting up and maintaining a link between computers NIC CONNECTION

Sends data from the network layer to the physical layer. Divides data to be sent into DATA FRAMES ETHERNET = PROTOCOL

Responsible for addressing and routing of data ROUTERS belong to this layer as they use logical adresses to direct data from the sender to receiver IP = PROTOCOL

Ensures data is reliably transferred for A to B without error. Responsible for making sure data is sent and received in the right order Transport layer is implemented in the sending and receiving computers but not in the routers on the path between them. TCP = PROTOCOL

The application layer provides interfaces to software to allow it to use the network HTTP/SMTP/FTP = PROTOCOL

The method of selecting the best possible path to send packets across a network. Quickest and cheapest

Domain Name System A DNS is a database that matches IP addresses to computer system resources If the DNS of the requests cannot find an address the request is passed onto a higher DNS An URL is searched on a computer This is sent to your ISP’s DNS where they will match the URL to an IP in an address book. The IP is sent back to you allowing you to communicate directly with the host server.

A type of network technology that provides a DEDICATED LINK between two devices. During the connection no other data can be transmitted on the same route. ADV - Reliable connection once established quick DIS - Takes time to establish connection

All computers on the network will be cabled into the hub When the hub receives a message it transmits it to all other computers on the system A hub cannot send and receive information at the same time causing problems in larger networks

Similar to a hub but ONLY SEND MESSAGES TO THE INTENDED COMPUTER Keeps a table of addresses for computers on a network Switches CAN send and receive at the same time

Connects two separate networks that use DIFFERENT PROTOCOLS LAN to WAN Gateways repackage data and convert it so it can be understood by the other networks protocols GATEWAYS ALLOW INTERNET ACCESS

Connect two separate networks that use the SAME PROTOCOLS A bridge will check for the presence of the receiving device before sending the message Checks to see if receiver has already had the message LAN to LAN