Computer Science Network Layers Please Explain

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GuyK03
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Hi, I'm doing a GCSE in OCR Computer Science, and I know nothing about packet switching or TCP/IP or Network Layers. Can someone please tell me the process that data would take as it is sent from Computer A to Computer B over the internet?
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Baby_Mama
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Enjoy
TCP/IP:
It's the protocol which controls how data is sent between networks.
The TCP part of TCP/IP - sets the rules of how devices connect on the network
- in charge of splitting the data into packets and reassembling them back into the correct order when its received.

The IP part of TCP/IP - is responsible for packet Switching.
Packet Switching is used by routers to direct data packets on the internet and other IP networks.

PACKET SWITCHING PROCESS:

1) Computer A splits data into packets to be sent across the network
2) each packet is given a packet number to show the order of the data
3) each router reads packet header and decides where the packet is to be sent.
4) as packets take different routes they can arrive in the wrong order so Computer B uses the packet number to reassemble them back in the right order
5) Computer B checks if all the data packets have been received
6) If it hasn't received all the data packets in a certain time (e.g. 10-15sec) it sends a timeout message back to Computer A.
7) If all the data packets have been received in the correct time and the checksum match a receipt confirmation is sent back to Computer A.

Checksum - a form of validation to check if payload( the data read by receiver) data isn't corrupt.

NETWORK LAYERS:
(definition) Layer - a group of protocols which have similar functions
-each layer servers the layer above it.
- layers are self-contained meaning the protocols in the layers do their job without needing to know what's happening in other layers.

LAYER 4 - turns data into applications and websites
Protocols present : HTTPS/HTTP/SMTP
LAYER 3 - controls data flow
Protocols present : TCP
LAYER 2 - makes connections between networks directing data packets
Protocols present : IP
LAYER 1 - responsible for how bits are sent as electrical signals over networks
Protocols present : Ethernet
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