U3 - NETWORKS Flashcards
PACKET CONTENTS
Error Check
Data
Return Address
Tracking Information
Sequence No.
Destination Address
SEQUENCE NO.
Tells the receiving device what order the packet goes in
TRACKING INFO
Allows the router to keep track of the data
ERROR CHECK
Authenticates the data / Makes sure it hasn’t been corrupted
RETURN ADDRESS
Contains the IP Address of the sending device in case an error occurs
DESTINATION ADDRESS
Says where the packet needs to go
NETWORK
A network consists of two or more devices that are connected together allowing them to communicate and exchange information
ROUTERS
Routers store all addresses of all the computers on a network. It can forward data to the correct destination.
PROTOCOLS
Protocols are agreed formats that allow networks to communicate.
EXAMPLE PROTOCOLS
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
TCP/IP STACK
Physical layer
Data link layer
Network layer
Transport layer
Application Layer
PHYSICAL LAYER
Transmits raw data
Consists of cables and switches
Deals with all aspects of setting up and maintaining a link between computers
NIC CONNECTION
DATA LINK LAYER
Sends data from the network layer to the physical layer.
Divides data to be sent into DATA FRAMES
ETHERNET = PROTOCOL
NETWORK LAYER
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
TRANSPORT LAYER
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
APPLICATION LAYER
The application layer provides interfaces to software to allow it to use the network
HTTP/SMTP/FTP = PROTOCOL
ROUTING
The method of selecting the best possible path to send packets across a network. Quickest and cheapest
DNS
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.
CIRCUIT SWITCHING
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
HUB
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
SWITCH
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
GATEWAYS
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
BRIDGES
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
