Chapter 1

Delay in Packet-Switched Networks

The most important delays are the node processing delay, queuing delay, transmission delay, and propagation delay.

• Processing delay
  The time required to examine the packet’s header and determine where to direct the packet is part of the **processing delay, **it also includes other factors, such as the time needed to check for bit-level errors in the packet that occurred
  in the transmission.
• Queuing Delay
  At the queue, the packet needs to wait to be transmitted onto the link. The length of the delay depends on the number
  of earlier-arriving packets that are queued and waiting for transmission onto the link.
• Transmission Delay
  The amount of time required to push all of the packet’s bits into the link. Denote the length if the packet by L bits, and the transmission rate of the link by R bits/sec, the Transmission Delay is L/R.
• Propagation Delay
  The time required to propagate from the start of link to destination router is the Propagation Delay. The speed depends on the physical medium of the link. The delay can be formulate by d/s, where the d is the distance between 2 nodes and the s is the speed of the signal propagate in the link medium

Packet Loss

When a packet arrived at the router, the router’s buffer is full, the packet will be dropped.