Four sources of delay if you use packet switching:
- Transmission delay: How fast the router can send data to the network
- Transmission delay = L/R, where L is packet length (bits) and R is bandwidth (bits per second)
- Limited bandwidth is biggest cause of transmission delay
- Nodal processing delay: Time taken to process the packet
- Check bit errors
- Determine output link
- Typically less than a millisecond
- Queueing delay: Time waiting at output link for transmission
- Depends on congestion level of router
- Propagation delay: How long it takes to travel from the router to the next point
- Propagation delay = d/v
- d = length of physical link
- v = propagation speed
Warning
Transmission delay and propagation delay are very different, don’t confuse the two.
