Qualities of Traffic
In packet-switched networks, quality of service is affected by various factors, which can be divided into “human” and “technical” factors. Human factors include: stability of service, availability of service, delays, user information. Technical factors include: reliability, scalability, effectiveness, maintainability, grade of service, etc.
Many things can happen to packets as they travel from origin to destination, resulting in the following problems as seen from the point of view of the sender and receiver:
- Low throughput
- Due to varying load from other users sharing the same network resources, the bit rate (the maximum throughput) that can be provided to a certain data stream may be too low for realtime multimedia services if all data streams get the same scheduling priority.
- Dropped packets
- The routers might fail to deliver (drop) some packets if their data is corrupted or they arrive when their buffers are already full. The receiving application may ask for this information to be retransmitted, possibly causing severe delays in the overall transmission.
- Errors
- Sometimes packets are corrupted due to bit errors caused by noise and interference, especially in wireless communications and long copper wires. The receiver has to detect this and, just as if the packet was dropped, may ask for this information to be retransmitted.
- Latency
- It might take a long time for each packet to reach its destination, because it gets held up in long queues, or takes a less direct route to avoid congestion. This is different from throughput, as the delay can build up over time, even if the throughput is almost normal. In some cases, excessive latency can render an application such as VoIP or online gaming unusable.
- Jitter
- Packets from the source will reach the destination with different delays. A packet's delay varies with its position in the queues of the routers along the path between source and destination and this position can vary unpredictably. This variation in delay is known as jitter and can seriously affect the quality of streaming audio and/or video.
- Out-of-order delivery
- When a collection of related packets is routed through a network, different packets may take different routes, each resulting in a different delay. The result is that the packets arrive in a different order than they were sent. This problem requires special additional protocols responsible for rearranging out-of-order packets to an isochronous state once they reach their destination. This is especially important for video and VoIP streams where quality is dramatically affected by both latency and lack of sequence.
Read more about this topic: Quality Of Service
Famous quotes containing the words qualities of, qualities and/or traffic:
“I am writing to resist the view that Europe and civilization are going to Hell. If I am being “crucified for an idea”Mthat is, the coherent idea around which my muddles accumulated—it is probably the idea that European culture ought to survive, that the best qualities of it ought to survive along with whatever cultures, in whatever universality. Against the propaganda of terror and the propaganda of luxury, have you a nice simple answer?”
—Ezra Pound (1885–1972)
“I should say tact was worth much more than wealth as a road to leadership.... I mean that subtle apprehension which teaches a person how to do and say the right thing at the right time. It coexists with very ordinary qualities, and yet many great geniuses are without it. Of all human qualities I consider it the most convenient—not always the highest; yet I would rather have it than many more shining qualities.”
—M. E. W. Sherwood (1826–1903)
“There was a girl who was running the traffic desk, and there was a woman who was on the overnight for radio as a producer, and my desk assistant was a woman. So when the world came to an end, we took over.”
—Marya McLaughlin, U.S. television newswoman. As quoted in Women in Television News, ch. 3, by Judith S. Gelfman (1976)