Three Categories of Quality Issues

Question 1

Delay

Answer 1

Delay Delay is the time required for a packet to travel from its source to its destination. You might
have witnessed delay on the evening news when the news anchor is talking via satellite to a
foreign news correspondent. Because of the satellite delay, the conversation begins to feel
unnatural.

Question 2

Jitter

Answer 2

Jitter Jitter is the uneven arrival of packets. For example, imagine a VoIP conversation where packet
1 arrives at a destination router. Then, 20 ms later, packet 2 arrives. After another 70 ms,
packet 3 arrives, and then packet 4 arrives 20 ms behind packet 3. This variation in arrival
times (that is, variable delay) is not dropping packets, but the jitter might be interpreted by the
listener as dropped packets.

Question 3

Drops

Answer 3

Drops Packet drops occur when a link is congested and a router’s interface queue overflows. Some
types of traffic, such as UDP traffic carrying voice packets, are not retransmitted if packets are
dropped.