ch. twelve
multimedia transmission
Summary
■ An analog signal is converted into a digital code by taking samples of the
analog signal’s amplitude at specific times.
■ Sampling rate is the number of times a signal is sampled during a specific
period.
■ Sampling frequency is the number of times a signal is sampled per second.
■ Jitter is the small staggers or hesitations in the delivery sequence of audio or
video data and is caused by latency or missing packets.
■ Video images typically occur at a minimum rate of 24 frames per second.
■ The term latency means the delay of data as it travels to its destination.
■ While latency with a delay of approximately 250 milliseconds will be noticed
by a user, it is acceptable.
■ The term codec represents software, hardware, or combination of software and
hardware that compresses and decompresses video and audio information.
■ X.25 is one of the early protocols used to transfer data over telephone lines.
■ Frame Relay is a packet switching protocol that typically uses leased lines
such as T1 to carry data over long distances.
■ The Asynchronous Transfer Mode (ATM) protocol is designed to carry audio,
video, and multimedia.
■ The five ATM classifications are CBR, VBR-NRT, VBR-RT, ABR, and UBR.
■ The maximum size of an ATM cell is 53 bytes, consisting of a 5-byte header
and a 48-byte payload.
■ Voice over IP (VoIP) is a technique that relies on the TCP/IP protocol suite to
carry audio and video data.
■ VoIP uses the UDP protocol when sending time-sensitive data, such as a
telephone conversation.
■ VoIP uses the TCP protocol when sending audio and video streaming data.
■ The H.323 protocol is used by telecommunications and telephone equipment.
■ A gateway is used to convert the TCP/IP protocol to the H.323 protocol.
■ The Session Initiation Protocol (SIP) is used for initiating, maintaining, and
terminating the exchange of data.
■ The Real-time Transport Protocol (RTP) is used to stream voice and video as
used in video conferencing and gaming.
■ A bandwidth shaper prioritizes network packets to ensure quality of service
for time-sensitive applications.
■ A protocol analyzer is an excellent tool for identifying VoIP-related problems.
■ Impedance mismatch refers to the effect of connecting two different
electronic audio systems that have different electronic characteristics.
Review Questions
Answer the following questions on a separate sheet of paper. Please do not write in this book.
1. Converting digital pulses to an analog waveform is called _____ conversion.
2. Converting an analog waveform to digital pulses is called _____ conversion.
3. What is jitter?
4. The delay of data from its origin to the final destination is called _____.
5. Name four factors that contribute to echo.
6. What is the principle use for MPEG compression?
7. What communications protocol is characterized by analog packets rather
than digital packets for communication?
8. What is the maximum data rate of X.25?
9. What protocol could be called an upgrade of the X.25 protocol?
10. What is the maximum data rate of Frame Relay?
11. Which scenario requires the Constant Bit Rate (CBR) classification of ATM
communications?
A. Live telephone conversation
B. FAX
C. Real-time broadcast of a movie
D. Business conference call
E. Cell phone conversation
F. Transfer of an image from an archive
12. Which ATM classification provides the best support for video conferencing?
13. What does the term Variable Bit Rate mean in reference to ATM
classifications?
14. What is the total length of a typical ATM cell including the header?
15. What happens when one of the ATM cells is destroyed or does not reach the
destination?
16. Why is the ATM cell payload so small (48 bytes)?
17. An ATM virtual path may contain two or more _____.
18. A Switched Virtual Circuit (SVC) is a (temporary, permanent) _____
connection between two devices on a network.
19. Based on what two factors will an ATM switch drop a cell?
20. Which VoIP protocol is used to establish and terminate a VoIP session?
21. Which VoIP protocol is used to stream multimedia in real-time between two
network nodes?
22. What is another name for bandwidth shaper?
23. What is the purpose of a bandwidth shaper?
24. What is the purpose of the QoS protocol?
25. What is the most common source of VoIP echo?
■ An analog signal is converted into a digital code by taking samples of the
analog signal’s amplitude at specific times.
■ Sampling rate is the number of times a signal is sampled during a specific
period.
■ Sampling frequency is the number of times a signal is sampled per second.
■ Jitter is the small staggers or hesitations in the delivery sequence of audio or
video data and is caused by latency or missing packets.
■ Video images typically occur at a minimum rate of 24 frames per second.
■ The term latency means the delay of data as it travels to its destination.
■ While latency with a delay of approximately 250 milliseconds will be noticed
by a user, it is acceptable.
■ The term codec represents software, hardware, or combination of software and
hardware that compresses and decompresses video and audio information.
■ X.25 is one of the early protocols used to transfer data over telephone lines.
■ Frame Relay is a packet switching protocol that typically uses leased lines
such as T1 to carry data over long distances.
■ The Asynchronous Transfer Mode (ATM) protocol is designed to carry audio,
video, and multimedia.
■ The five ATM classifications are CBR, VBR-NRT, VBR-RT, ABR, and UBR.
■ The maximum size of an ATM cell is 53 bytes, consisting of a 5-byte header
and a 48-byte payload.
■ Voice over IP (VoIP) is a technique that relies on the TCP/IP protocol suite to
carry audio and video data.
■ VoIP uses the UDP protocol when sending time-sensitive data, such as a
telephone conversation.
■ VoIP uses the TCP protocol when sending audio and video streaming data.
■ The H.323 protocol is used by telecommunications and telephone equipment.
■ A gateway is used to convert the TCP/IP protocol to the H.323 protocol.
■ The Session Initiation Protocol (SIP) is used for initiating, maintaining, and
terminating the exchange of data.
■ The Real-time Transport Protocol (RTP) is used to stream voice and video as
used in video conferencing and gaming.
■ A bandwidth shaper prioritizes network packets to ensure quality of service
for time-sensitive applications.
■ A protocol analyzer is an excellent tool for identifying VoIP-related problems.
■ Impedance mismatch refers to the effect of connecting two different
electronic audio systems that have different electronic characteristics.
Review Questions
Answer the following questions on a separate sheet of paper. Please do not write in this book.
1. Converting digital pulses to an analog waveform is called _____ conversion.
2. Converting an analog waveform to digital pulses is called _____ conversion.
3. What is jitter?
4. The delay of data from its origin to the final destination is called _____.
5. Name four factors that contribute to echo.
6. What is the principle use for MPEG compression?
7. What communications protocol is characterized by analog packets rather
than digital packets for communication?
8. What is the maximum data rate of X.25?
9. What protocol could be called an upgrade of the X.25 protocol?
10. What is the maximum data rate of Frame Relay?
11. Which scenario requires the Constant Bit Rate (CBR) classification of ATM
communications?
A. Live telephone conversation
B. FAX
C. Real-time broadcast of a movie
D. Business conference call
E. Cell phone conversation
F. Transfer of an image from an archive
12. Which ATM classification provides the best support for video conferencing?
13. What does the term Variable Bit Rate mean in reference to ATM
classifications?
14. What is the total length of a typical ATM cell including the header?
15. What happens when one of the ATM cells is destroyed or does not reach the
destination?
16. Why is the ATM cell payload so small (48 bytes)?
17. An ATM virtual path may contain two or more _____.
18. A Switched Virtual Circuit (SVC) is a (temporary, permanent) _____
connection between two devices on a network.
19. Based on what two factors will an ATM switch drop a cell?
20. Which VoIP protocol is used to establish and terminate a VoIP session?
21. Which VoIP protocol is used to stream multimedia in real-time between two
network nodes?
22. What is another name for bandwidth shaper?
23. What is the purpose of a bandwidth shaper?
24. What is the purpose of the QoS protocol?
25. What is the most common source of VoIP echo?