Switching Types

Switching is the fundamental mechanism of moving data from an input port to an output port. The history of networking is the battle between two philosophies: Circuit Switching (Telephone Network) and Packet Switching (Internet).

1. Circuit Switching (The Old Way)

In a circuit-switched network, a dedicated physical path is established between two nodes before they can communicate.

  • Setup Phase: You dial a number. The switches reserve a path.
  • Data Phase: You talk. The bandwidth is 100% yours.
  • Teardown Phase: You hang up. The path is released.

[!WARNING] The Problem: If you stop talking for 10 seconds, the line is silent, but the resources are still reserved. Nobody else can use them. This is incredibly inefficient for data traffic, which is “bursty” (e.g., loading a webpage takes 1s, reading it takes 60s).

2. Packet Switching (The Internet Way)

In a packet-switched network, data is chopped into small chunks called Packets. Each packet fights for survival.

  • No Reservation: You just send packets.
  • Store and Forward: Routers receive a packet, store it in memory, look at the address, and forward it.
  • Statistical Multiplexing: If 10 users share a 100Mbps link, and only 1 is active, they get 100Mbps. If all 10 are active, they get 10Mbps.

[!TIP] Why it won: Packet switching allows us to oversubscribe the network. An ISP can sell 1Gbps plans to 100 people on a single 10Gbps line because statistically, they won’t all use it at the exact same millisecond.

3. Interactive: The Multiplexing Simulator

Visualize why Packet Switching handles “Bursty” traffic better.

  • Scenario: 4 Users sharing 1 Wire.
  • Circuit: Each user gets a dedicated slice (Slot). If they don’t use it, it’s wasted.
  • Packet: Users share a queue. If one is silent, others use the space.
User A (Silent)
User B (Active)
User C (Silent)
User D (Active)
Circuit (TDM)
50% Wasted Capacity
Packet (Stat Mux)
100% Utilization

4. Comparison

Feature Circuit Switching Packet Switching
Path Dedicated (Physical) Dynamic (Routing)
Bandwidth Fixed per user Shared (Multiplexed)
Utilization Low (Silence is wasted) High (Fill every gap)
Congestion Blocked Call (Can’t dial) Queuing Delay (Lag)
Example PSTN (Phone Network) TCP/IP (Internet)