Packet Switching

networking

Definition

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Packet Switching

Let be a computer network with nodes and links .

Packet switching is a data transmission method in which a message is partitioned into a sequence of packets , each routed independently through from a source to a destination .

Each packet consists of a header carrying routing metadata (source, destination, sequence number) and a payload carrying a fragment of the message.

At each intermediate node , the router inspects and selects an outgoing link according to a forwarding table . Packets are stored-and-forwarded: a node receives the entire packet before forwarding it.

Mechanism

No dedicated path

No physical or logical circuit is established before transmission. Each packet is an independent datagram that may follow a different route through .

Statistical Multiplexing

Links are shared by packets from many source–destination pairs. Resource allocation is on-demand rather than pre-allocated. This is called statistical multiplexing.

Store-and-Forward

A packet arriving at a node must be fully received and buffered before determines the next hop and begins transmission. This introduces a per-hop delay proportional to packet size.

Routing and forwarding

Each node maintains a forwarding table mapping each destination to an outgoing link (or for local delivery). The table is populated by a routing protocol.