Which of the following best describes jitter? (Select the best answer.)
A.
serialization delay
B.
variation in delay
C.
end-to-end delay
D.
dropped packets
E.
flapping links
Explanation:
Jitter is a variation in delay, which can cause packets to arrive out of sequence or at a different rate than they
were sent. Voice over IP (VoIP) traffic is heavily affected by jitter because voice traffic is timesensitive and
requires that the destination host receive the voice traffic in the order, and at the same rate, it was sent. When
jitter is present, the end user might experience choppiness in the audio connection. A dejitter buffer at the
destination is used to collect packets, sort them into the proper sequence based on Realtime Transport
Protocol (RTP) time stamps, and release them to the voice application. Although a dejitter buffer can decrease
jitter, it can increase delay as packets sit in the buffer. Jitter can be mitigated by increasing bandwidth, using
Quality of Service (QoS) mechanisms to prioritize timesensitive traffic, using Compressed RTP (cRTP) to
compress headers, and using Stacker and Predictor to compress payloads.
Jitter is not dropped packets, nor is it caused by dropped packets. Congested networks often cause dropped
packets. Dropped packets can cause clips, or breaks, in the audio stream. However, voice traffic is more
tolerant of dropped packets than of delayed packets, because a small amount of packet loss is not noticeable
to the human ear. Packet loss can be mitigated by implementing QoS and congestion avoidance mechanisms,
increasing bandwidth, and increasing buffer space. In addition, some codecs can correct small amounts of
packet loss.
Jitter is not serialization delay. Serialization delay is the time required to place a packet onto a medium, such as
a copper or fiberoptic cable. Serialization delay is directly related to the clocking method and the bandwidth of
the line.
Jitter is not endtoend delay. Endtoend delay is the sum of the processing, queuing, serialization, and
propagation delays in the traffic path between the source of the packet and the destination of the packet.
Therefore, the total network delay between the source of the packet and its destination is considered endto-end
delay. Endtoend delay can be mitigated by QoS mechanisms.
Jitter is not flapping links, although jitter can be caused by a flapping link. A flapping link is an interface that
alternates between enabled and disabled, often because of a faulty cable or network card. Flapping links can
cause packets to take different routes through a network, which can introduce jitter and packet loss.https://www.cisco.com/c/en/us/support/docs/voice/voice-quality/18902-jitter-packet-voice.html