Measuring Link Performance
Some values #
The Bandwidth of a link is the number of bits sent/received per unit time (measured in bps, bits per second).
The Propagation delay of a link is the time it takes a bit to travel along the link (measured in seconds). It is analogous to the ’length’ of the link.
Bandwidth-delay product (BDP) is the product of bandwidth and propagation delay, measured in bits. It is analogous to the total capacity of a link (how many bits can be in the link at the same time).
Transmission delay is equal to Packet Size / Link Bandwidth. It describes how long it will take before the entire packet has entered the link.
Queueing delay describes the amount of time a packet exists in a router’s queue when transient overload occurs.
Packet Delay is equal to the sum of transmission delay, propagation delay, and queueing delay.
Router Capacity is equal to the number of external ports multiplied by the speed of each port.
- Example: a router with 4 100Mbps ports and 1 1Gbps port will have a total capacity of 0.4 + 1 = 1.4Gbps.