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Unit 3 Networks - Part 3 Transmitions of Data - Coggle Diagram
Unit 3 Networks - Part 3 Transmitions of Data
Circuit Switching
Circuit switching was a globally accepted standard until superseded by packet switching.
Circuit switching requires a series of connections to be made to form a single route and that all data traverses the same route. This is susceptible to interception and failure as failure of any one connection results in failure of the entire route.
Packet Switching
This is how data is transmitted across most networks/the internet:
Data are split into packets before transmission
Packets are sent in-order but might arrive out of order
Each packets can take a different route to its destination
Data is reassembled at the destination
Packet switching is less susceptible to interception and is more reliable because if a route fails then the packet can use an alternate route. Missing packets are resent when needed.
Contents of a packet
Length is the number of bits in the packet
Packet ID is needed so that, afterwards, data from multiple packets can be arranged into the correct order
Source address is the IP address of the device that sent the data.
Destination address is the IP of the device that should receive the data
Protocol is an indication of which protocol (HTTP, FTP, SMTP, etc.) has been used to form the packet.
Data is the reason a packet is being sent in the first place, Eventually, all packet components are discarded except for the data itself.
Checksum is a technique that verifies that the data that was sent matches the data that was received
Benefits of transmitting packets using routers:
Each packet can take a different route through network which therefore makes it secure as it is difficult to intercept all the packets
Packets are less likely to be affected by network failure because they can simply take an alternative route
Each packet can take a different route through network which means more efficient use of data lines as packet can use least busy route
Each packet can take a different route through network which means a node failure does not stop the packet reaching its destination
Routing
Routing is the name given to the method of selecting paths along which packets are sent on a computer network.
Specialist hardware such as routers, switches, bridges and gateways construct in their memory a routing table, which stores a number of paths along which it is best to send packets to reach a specific destination. Maintaining accurate routing tables is essential for ensuring that packets are delivered as quickly as possible.