1. Circuit Switching

<aside> 📖 Features

• Each call has its own private, guaranteed, isolated data rate from end-to-end
• A call has three phases:
  1. Establish circuit from end-to-end, dialing
  2. Communicate
  3. Close circuit, tear down
• Originally, a circuit was an end-to-end physical wire.
• Nowadays, a circuit is like a virtual private wire. </aside>

<aside> 📖 Problems

• Inefficient
• Diverse Rates
• State Management </aside>

2. Packet Switching

<aside> 📖 Packet switches have buffers

Buffers hold packets:

• When two or more packets arrive at the same time
• During periods of congestion </aside>

<aside> 📖 Features

• Packets are routed individually, by looking up address in router’s local table
• All packets share the full capacity of a link
• The routers maintain no per-communication state </aside>

<aside> 📖 Why the Internet uses Packet Switching?

• Efficient use of expensive links
• Resilience to failure of links & routers
• The Internet was originally designed as an interconnection of the existing networks </aside>