You are troubleshooting voice audio problems on your company’s VoIP network. The network carries both data
and VoIP traffic. You have obtained the following measurements:
Jitter: 30 ms
Packet loss: 1 percent
End-to-end delay: 250 ms
Which of the following best describes why your company’s network is experiencing voice audio problems?

A.
The jitter is too high.

B.
The packet loss is too high.

C.
The end-to-end delay is too high.

D.
VoIP traffic should not be carried on the same network as data traffic.

Explanation:
Your company’s network is most likely experiencing voice audio problems because the end-to-end delay is too
high. Short delays and low packet loss on a Voice over IP (VoIP) network help protect the rate at which bits flow
over the network. Cisco recommends a maximum end-to-end delay of 200 ms. The International
Telecommunication Union (ITU) considers an end-to-end delay of 150 ms or less to be acceptable for high
voice quality. Delay, which is also called latency, can introduce interruptions in conversation flow, causing the
speakers at each end of the circuit to interrupt each other. End-to-end delay can be mitigated by implementingQuality of Service (QoS) mechanisms.
It is not likely that the reason your company’s network is experiencing voice audio problems is because packet
loss is too high. Cisco recommends a maximum packet loss of 1 percent for VoIP traffic. Packet loss is often
caused when networks become congested and packets are dropped. 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. Some codecs can correct small
amounts of packet loss. On networks with limited bandwidth, a low-bit-rate codec can mitigate packet loss.
However, the overall quality of the audio will be reduced. Packet loss can also be mitigated by implementing
QoS mechanisms.
It is not likely that the reason your company’s network is experiencing voice audio problems is because the jitter
is too high. Cisco recommends a maximum jitter of 30 ms for VoIP traffic. Jitter is a variation in delay, which
can cause voice traffic to arrive at different times, thereby causing breaks, or choppiness, in the audio stream.
Jitter can be mitigated by implementing QoS mechanisms. The effects of VoIP issues like jitter and latency on a
network can be analyzed by using data analysis techniques such as Mean Opinion Score (MOS) or RFactor.
It is not likely that the reason your company’s network is experiencing voice audio problems is because VoIP
traffic is carried on the same network as data traffic. VoIP traffic can be carried on the same network as data
traffic. However, data traffic is usually more tolerant of dropped packets and delay than VoIP traffic. Therefore,
VoIP traffic is typically given priority over data traffic.

Cisco: Quality of Service for Voice over IP (PDF)