# Sources of Packet Delay

$d_\text{nodal}$ is the sum of:

• $d_\text{processing}$ is the time checking for bit errors. Typically finishes in milliseconds.

• $d_\text{queueing delay}$ is the time waiting in the memory if the router is busy transmitting something else.

• $d_\text{transmission delay} = {\text{packet size} \over \text{bandwidth}}$

• $d_\text{propagation delay} = {\text{cable length} \over c}$ is the physical constraint of propagation. $c$ is the speed of connection, usually the speed of light.

• Propagation Delay