Review Questions

Answer the following questions, and then refer to Appendix A for the answers.

1. What steps are involved in converting analog signals to digital signals?

2. What is pulse amplitude modulation?

3. What is pulse code modulation?

4. Match the following terms with their definitions: Terms:

■ Quantization

■ Companding

Step 3 Step 4 Step 5

■ Logarithmic compression


■ Converting an analog sample to a digital code word

■ Compression increases as the sample signal increases

■ Removing nonspeech components

■ Compressing and expanding signals

6. What are some differences between a PBX and a PSTN switch?

7. What are some of the call features provided by PBXs?

8. How does having a PBX save on communication costs?

9. Match the following terms with their definitions: Terms:

■ PSTN switch trunk Definitions:

■ Connects CO switches to PBXs

■ Physical cabling

■ Communication path between two telephony systems

■ Connects PBXs

■ Interconnects CO switches

■ Communication between PBX and business telephone

10. What is the difference between local-loop and trunk signaling?

11. What is the difference between channel associated signaling (CAS) and common channel signaling (CCS)?

12. Which signaling method allows standardized communication between PBXs?

13. Which signaling method is used between PSTN switches?

14. Describe how a telephone call is routed from location A to location B through the PSTN using the NANP.

15. Match the following terms with each part of the following telephone number used to call someone in North America:

Telephone Number: 1-416-555-1212


16. What is the difference between VoIP and IP telephony?

17. What role does an H.323 terminal play in voice networks?

18. What is the difference between an H.323 gateway and an H.323 gatekeeper?

19. What is a voice port?

20. What does Cisco Unified Communications Manager do?

21. What are the four components of IP telephony architecture?

22. How does IP telephony lower costs?

23. Describe the difference between a multisite WAN design model with distributed call processing and a multisite WAN design model with centralized call processing.

24. Match the protocols with their descriptions: Protocols:


■ A Cisco-proprietary terminal control protocol used for messaging between IP phones and Cisco Unified Communications Manager

■ A client/server protocol in which call agents control endpoints

■ An IETF standard for multimedia conferencing over IP

■ An ITU-T standard for packet-based audio, video, and data communications across IP-based networks

25. Complete the following sentence:

Dejitter buffers are used on_of the network to smooth out delay variability.

a. The originating side b. The receiving side c. All sides

26. What is the generally acceptable one-way delay limit for good-quality voice?

27. Match the following terms with their definitions: Terms:

■ Processing delay

■ Propagation delay

■ Echo Definitions:

■ Variation in the delay of received packets

■ Audible leak of the caller's voice into the receive (return) path

■ Length of time it takes a signal to travel the distance between the sending and receiving endpoints

■ Time the DSP takes to process a block of PCM samples

28. What is link fragmentation and interleaving (LFI)?

29. Is a voice packet loss always audible?

30. Match each of the following coding standards with a data rate or rates that it supports: Coding standards:

31. Which of the following ITU voice coding standards results in the highest mean opinion score (MOS): G.711, G.723.1, G.726, G.728, or G.729?

32. What is the difference between low-, medium-, and high-complexity codecs?

33. What protocols are used to transport voice conversation traffic?

34. Match the following terms with their definitions: Terms:

■ RTCP Definitions:

■ Used only if a gatekeeper is present

■ Uses Q.931 to establish a connection between two terminals

■ Used by hosts communicating with RTP to monitor the session

■ Carries control messages that govern voice operation

35. What does voice activity detection do?

36. What does compressed RTP do?

37. Which of these codecs have relatively more IP header overhead compared to the payload? Arrange them in descending order.

38. Which queuing mechanism is recommended for most VoIP designs?

39. What is the purpose of the Call Admission Control (CAC) mechanisms?

40. Describe how CAC with RSVP works.

41. True or false: When deploying voice, it is recommended that the data and voice traffic from a user travel on the same VLAN.

42. How many centum call seconds (CCS) equals five Erlangs?

43. What does a GoS of P05 mean?

44. If your call logger says that 290 calls are made on a trunk group in the busiest hour and the average call duration is 180 seconds, what is the busy hour traffic (in Erlangs)?

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This chapter describes wireless network design principles and includes the following sections:

■ Introduction to Wireless Technology

■ The Cisco Unified Wireless Network

■ Designing Wireless Networks with Lightweight Access Points and Wireless LAN Controllers

■ References

■ Case Study: ACMC Hospital UWN Considerations

■ Review Questions

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