Definition

Switching is the process of moving data from a source to a destination across an interconnection of links and switching nodes. A switching node establishes how data units traverse the network (route selection, resource allocation, buffering and forwarding).

Main switching paradigms

1. Circuit switching
2. Message switching
3. Packet switching (most used today)

1) Circuit switching

• Idea: A dedicated path (circuit) is established between sender and receiver before data transfer, remains reserved until teardown.
• Phases:
  1. Setup (reserve resources)
  2. Data transfer (uses reserved resources)
  3. Teardown (release resources)
• Resource allocation: can be by FDM (frequency slots) or TDM (time slots).
• Properties: fixed bandwidth during call, predictable delay, blocking possible (calls denied if no free circuit).
• Examples: Traditional telephone network (PSTN).
• Pros: predictable QoS, low per-packet processing.
• Cons: inefficient for bursty traffic (resources idle during silence), blocking, slower call setup.

2) Message switching