Chapter 28 Real-Time Traffic over the Internet
CONTENTS <ul><li>CHARACTERISTICS </li></ul><ul><li>RTP </li></ul><ul><li>RTCP </li></ul>
Figure  28-1 Real-time multimedia traffic
In real-time traffic, if we ignore  propagation delay,  the production, transmission,  and use of data takes  place at the...
Example 1 An example of non-real-time multimedia traffic is the downloading of a video from the Internet. The video has al...
Figure  28-2 Non-real time multimedia traffic
Example 2 Now let us consider an example of real-time multimedia traffic. Consider a video conference in which a camera is...
Figure  28-3 Real-time multimedia traffic
CHARACTERISTICS 28.1
Figure  28-4 Time relationship
Figure  28-5 Jitter
Jitter is introduced in real-time  data by the  delay between packets.
Figure  28-6 Timestamp
To prevent jitter,  we can timestamp the  packets and separate  the arrival time  from the playback time.
Figure  28-7 Playback buffer
A playback buffer is  required for real-time traffic.
A sequence number on  each packet is  required for real-time traffic.
Real-time traffic needs  the support of multicasting.
Translation means changing the  encoding of a payload to a lower  quality to match the bandwidth  of the receiving network.
Mixing means combining  several streams of traffic  into one stream.
TCP, with all its sophistication,  is not suitable  for real-time multimedia  traffic because  we cannot allow  retransmis...
UDP is more suitable than  TCP for real-time traffic.  However, we need the services of  RTP, another transport layer  pro...
RTP 28.2
Figure  28-8 RTP
Figure  28-9 RTP packet header format
RTP uses  a temporary even-numbered  UDP port.
RTCP 28.3
Figure  28-10 RTCP message types
RTCP uses an odd-numbered UDP  port number that follows  the port number selected  for RTP.
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Ch28

  1. 1. Chapter 28 Real-Time Traffic over the Internet
  2. 2. CONTENTS <ul><li>CHARACTERISTICS </li></ul><ul><li>RTP </li></ul><ul><li>RTCP </li></ul>
  3. 3. Figure 28-1 Real-time multimedia traffic
  4. 4. In real-time traffic, if we ignore propagation delay, the production, transmission, and use of data takes place at the same time.
  5. 5. Example 1 An example of non-real-time multimedia traffic is the downloading of a video from the Internet. The video has already been made; it’s a finished product. A client HTTP is used to download the video from an HTTP server and the user views the video at a later time. The production, transmission, and use all happen at different times. Figure 28.2 shows this situation
  6. 6. Figure 28-2 Non-real time multimedia traffic
  7. 7. Example 2 Now let us consider an example of real-time multimedia traffic. Consider a video conference in which a camera is connected to a server that transmits video information as it is produced. Everything that happens at the server site can be displayed on the computer at the client site. This is both multimedia (video) and real-time traffic (production and use at the same time). Figure 28.3 shows the situation.
  8. 8. Figure 28-3 Real-time multimedia traffic
  9. 9. CHARACTERISTICS 28.1
  10. 10. Figure 28-4 Time relationship
  11. 11. Figure 28-5 Jitter
  12. 12. Jitter is introduced in real-time data by the delay between packets.
  13. 13. Figure 28-6 Timestamp
  14. 14. To prevent jitter, we can timestamp the packets and separate the arrival time from the playback time.
  15. 15. Figure 28-7 Playback buffer
  16. 16. A playback buffer is required for real-time traffic.
  17. 17. A sequence number on each packet is required for real-time traffic.
  18. 18. Real-time traffic needs the support of multicasting.
  19. 19. Translation means changing the encoding of a payload to a lower quality to match the bandwidth of the receiving network.
  20. 20. Mixing means combining several streams of traffic into one stream.
  21. 21. TCP, with all its sophistication, is not suitable for real-time multimedia traffic because we cannot allow retransmission of packets.
  22. 22. UDP is more suitable than TCP for real-time traffic. However, we need the services of RTP, another transport layer protocol to make up the deficiencies of UDP.
  23. 23. RTP 28.2
  24. 24. Figure 28-8 RTP
  25. 25. Figure 28-9 RTP packet header format
  26. 26. RTP uses a temporary even-numbered UDP port.
  27. 27. RTCP 28.3
  28. 28. Figure 28-10 RTCP message types
  29. 29. RTCP uses an odd-numbered UDP port number that follows the port number selected for RTP.

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