Latency is the average travel time it takes for a packet to reach its destination.

1. If there is too much traffic on the line, or if a voice packet gets stuck behind a large data packet (such as an email attachment), the voice packet will be delayed to the point that the quality of the call is compromised.
2. The maximum amount of latency that a voice call can tolerate one way is 150 milliseconds (100 milliseconds is optimum).

Packet loss is a common occurrence in data networks, but computers and applications are designed to simply request a retransmission of lost packets.

1. Dropped voice packets, on the other hand, are discarded, not retransmitted.
2. Voice traffic can tolerate less than a 3 percent loss of packets (1% is optimum) before callers experience disconcerting gaps in conversation.

In order for voice to be intelligible, consecutive voice packets must arrive at regular intervals. Jitter describes the degree of variability in packet arrivals, which can be caused by bursts of data traffic or just too much traffic on the line.