Summary CIE iGCSE Computer Science | Data Transmission

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Theory 7 - Data Transmission




Packets

2.1.1




Theory 7 - Data Transmission 1

, Data is split into smaller units called packets to be transmitted, to reduce the risk of
the entire payload being lost or damaged.

Structure of a Packet
PACKET HEADER

Destination IP Address.

Sender’s IP Address.

Packet Number.

PAYLOAD

The data being transmitted.

TRAILER

Marks the end of the packet.

Packet Switching
Each packet is assigned a sequence number before being sent.

Each packet can take its own route to the destination based on congestion.

Routers are responsible for controlling the route each packet takes.

Packets may arrive out of order. Once the final packet arrives, they are re-orded
correctly.


Data Transmission

2.1.2-2.1.3

Serial vs Parallel
Serial Data Transmission

Individual bits of data are sent one at a time via a single cable.

Parallel Data Transmission

Individual bits of data are sent simultaneously via a series of cables.

Can travel at different speeds due to tiny imperfections in the cable, so bits
arrive out of sync, a problem known as skew.



Theory 7 - Data Transmission 2