A company implements video conferencing over IP on their Ethernet LAN. The users notice that the network slows down, and the video either stutters or fails completely. What is the most likely reason for this?

A.
minimum cell rate (MCR)

B.
quality of seivice (QoS)

C.
modulation

D.
packet switching exchange (PSE)

E.
reliable transport protocol (RTP)

Explanation:
This question is to examine QoS.
Quality of Service is a network security mechanism, which is used to resolve the network delay problem. This mechanism is essential to multimedia application. When the network is overloaded, QoS will prevent a possible delay in the important data transmission and ensure the efficient operation of the network.
The correct answer is B.