is called propagation delay. When distances are short, propagation delay is negligible. As
distances increase, delay also increases.
of light. Light travels in a vacuum at a speed of 186,000 miles per second. Electrons travel
through copper or fiber at 125,000 miles per second. Devices that forward the packet add to the
delay while handling the packets. In integrated networks, delay can contribute significantly to
voice degradation. Effective voice communication is all about timing. Voice information has
characteristic timing. A particular syllable of a word is uttered with an interval of time between
it and the following syllable. Sometimes a speaker pauses for effect. If a voice network is
impacted by unacceptable delay, the speech becomes corrupted.
delay should occur.
must address. Voice networks expect consistent and predictable real-time delivery. If the
packets arrive at an unexpected rate, the network can be described to be in a state of jitter.
Jitter is particularly disruptive to audio communications because it can cause pops and
clicks that can be heard on the audio line.
starts talking without realizing that the other person hasn't finished (because the other person's
conversation is late in arriving). This might be acceptable for walkie-talkie conversation or for
long-distance satellite communications, but it is unacceptable for voice networks.
the far-end telephone equipment back into the speaker's ear. Echo can become a problem when
the round-trip delay becomes greater than 50 ms. Voice over data networks must address the
echo problem.