Nov 15, 2007

Processing vs Queuing vs Serialization vs Propagation vs End-to-End delay

1. Processing delay:
The time that it takes for a router (or Layer 3 switch) to take the packet from an input interface and put it into the output queue of the output interface. The processing delay depends on various factors:
  • CPU speed
  • CPU utilization
  • IP switching mode
  • Router architecture
  • Configured features on both the input and output interfaces

2. Queuing delay:
The time that a packet resides in the output queue of a router. Queuing delay depends on the number of packets already in the queue and their sizes. Queuing delay also depends on the bandwidth of the interface and the queuing mechanism.

3. Serialization delay:
The time that it takes to place a frame on the physical medium for
transport. This delay is typically inversely proportional to the link bandwidth.

4. Propagation delay:
The time that it takes for the packet to cross the link from one end to the other. This time usually depends on the type of media. (For example, satellite links produce the longest propagation delay because of the high altitudes of communications
satellites.)

5. End-to-end delay:
Equals the sum of all propagation, processing, serialization, and queuing delays in the path.

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