switching-methods

Packetising

What is packetising?

• Packetising is the process of dividing a large message into smaller, manageable units called packets

• Each packet can be transmitted individually across a network

Structure of a packet

• Each packet typically contains:

  • Header – contains control information such as:

    • Source IP address – who sent the packet

    • Destination IP address – where it’s going

    • Sequence number – used to reassemble packets in the correct order

    • Protocol – e.g. TCP or UDP

    • Packet length – the size of the packet

    • Checksum – used for error checking

  • Payload – the actual data being sent

  • Footer (trailer) – may include extra error-checking or control information

Packet transmission & reassembly

• Once packetised and encapsulated with headers, packets are transmitted independently

• They may travel along different routes through the network

• At the destination, packets are reassembled into the original message using sequence numbers

Circuit & packet switching

What is packet switching?

• Packet switching is a communication method where data is broken into packets and sent across a shared network

• Each packet may take a different path to the destination and is reassembled on arrival

Benefits:

• Efficient use of network bandwidth

• More reliable – only lost or corrupted packets need to be resent

• Lower cost – network resources are shared

Drawbacks:

• Not ideal for real-time applications like VoIP or video calls

• Packets can arrive out of order and require reassembly

• Network congestion may lead to packet delay or loss

What is circuit switching?

• Circuit switching is another communication method where data is broken into packets and sent across a shared network

• Circuit switching sets up a dedicated communication path between two devices for the duration of a session (like a traditional phone call)

Benefits:

• Ideal for real-time communication – steady and continuous data flow

• No delays once the circuit is established

• Data arrives in order

Drawbacks:

• Less efficient – resources remain reserved even when not in use

• Higher cost due to dedicated lines

• Less scalable and flexible for large networks

Packet switching vs circuit switching