Network+ Guide to Networks, 6th Edition
Chapter 12 Solutions
Review Questions

1. You have decided to establish a VoIP system in your home. Which of the following devices is necessary to connect your analog telephone to your VoIP server?
a. Codec
b. IP-PBX
c. Softphone
d. ATA 2. Skype, the popular Internet telephony service, provides a user with what type of interface?
a. IP phone
b. Analog telephone
c. Softphone
d. IP-PBX 3. A company’s use of VoIP on its WAN to avoid long distance telephone charges is known as:
a. Toll bypass
b. WAN redirect
c. Fee gauging
d. Circuit redirect 4. Which of the following is the most popular signaling protocol used on traditional, circuit-switched PSTN connections?
a. SIP
b. SS7
c. H.323
d. MEGACO 5. Watching a YouTube video on the Web is an example of which of the following types of video-over-IP services?
a. Videoconferencing
b. Streaming video
c. IP multicasting
d. IPTV 6. In an IPTV system, which of the following functions does a set top box perform?
a. Decodes video signals and issues them to a television
b. Determines the appropriate amount of bandwidth necessary to deliver a requested video and adjusts the connection accordingly
c. Interprets multicast routing protocols to determine the most efficient means of distributing video signals
d. Generates video content based on a subscriber’s channel selection 7. What type of video-over-IP service relies on full-duplex communication?
a. Webcasting
b. Streaming video
c. Videoconferencing
d. IPTV 8. What protocol manages addressing for multicast groups?
a. IGMP b. MGCP c. MEGACO d. H.245 9. Which of the following protocols would be used by a video bridge to invite a video phone to join a videoconference? a. MGCP b. H.225 c. IGMP d. RSVP 10. Suppose your organization’s PSTN and VoIP systems are integrated, and that your VoIP system adheres to architecture specified in H.323. Which of the following performs translation between the PSTN’s signaling protocols and H.323 on your network?
a. H.323 terminal b. H.323 gatekeeper c. H.323 gateway d. H.323 zone 11. You are using Skype to initiate a video call with a friend in another state. Which of the following protocols is generating segments at the Transport layer of this transmission? a. ICMP b. TCP c. FTP d. UDP 12. What function does the H.225 protocol provide, as part of the H.323 VoIP specification? a. Handles call setup, call routing, and call termination b. Controls communication between media gateways and media gateway controllers c. Ensures that signals issued to an H.323 terminal are in a format that the terminal can interpret d. Indicates priority of each IP datagram 13. In SIP, which of the following network elements maintains a database with network address information for every SIP client? a. Redirect server b. Registrar server c. Domain server d. Proxy server 14. Which of the following are reasons for choosing SIP over H.323? (Choose two.) a. SIP is an older, more reliable standard. b. SIP has limited functionality, which makes it more flexible. c. SIP messages use fewer processing resources. d. SIP includes QoS mechanisms that make it more dependable. e. SIP supports a wider range of voice and video codecs. 15. Which of the following devices enable multiple media gateways to communicate? a. VoIP router b. IP-PBX c. MGC d. IP phone 16. At what layer of the OSI model does RTP operate? a. Transport b. Presentation c. Session d. Application 17. What can RTCP do that RTP cannot? a. Issue timestamps for every transmission b. Assign sequence numbers to each packet in a transmission c. Report on the degree of packet loss and delay in a connection d. Modify each IP datagram to assign a priority level 18. How does RSVP help improve QoS? a. It assigns a label to each IP datagram that will be read and modified by every router in the data’s path. b. It continually assesses the status of likely routes in the transmission’s path and dynamically modifies IP datagrams as they’re issued with instructions for following the best path. c. It modifies the Priority field in each IP datagram so that high-bandwidth applications are given precedence over low-bandwidth applications. d. It establishes a path between the sender and receiver that is guaranteed to supply sufficient bandwidth for the transmission. 19. The Traffic Class field in an IPv6 datagram serves the same function as which of the following fields in an IPv4 datagram?
a. TTL
b. DiffServ
c. RSVP
d. Padding 20. On a VoIP network that uses the DiffServ QoS technique, which of the following makes certain that a router forwards packets within a given time period?
a. Assured Forwarding
b. Superior Forwarding
c. Expedited Forwarding
d. Best-effort Forwarding

Hands-On Projects

Project 12-1
In this project, students use the Internet to research three offsite VoIP providers (for instance, Nextiva, RingCentral, and Vonage). First, students determine which of the features listed in Step 1 each provider offers. Next, students choose one of the providers to investigate more closely. They research costs for an organization with 10 phone extensions to use the service for a year, then determine how much it would cost an organization of 200 phone extensions to use the service for a year. Finally, students research Skype to learn how it compares to the three business VoIP providers they investigated previously.

Project 12-2
In this project students research and design an onsite VoIP solution using Cisco, Avaya, or Nortel equipment. First, they determine what kind of equipment they need for an organization of 50 phone extensions. Then students sketch a VoIP network design for the organization of 50. Next, they determine costs for the equipment and bandwidth needed to make this work, assuming that the solution doesn’t reuse devices that already exist on the network. Finally, they list advantages and disadvantages of using an onsite solution versus an offsite solution.

Students should recognize that the largest single drawback to implementing an onsite solution is cost. Another drawback is the technical complexity of the solution. Significant advantages are customizability and accountability (because if a VoIP provider’s network fails, or worse, if the provider goes out of business, there is nothing the customer can do about loss of service).

Project 12-3
In this project students are asked to apply what they have learned in this chapter and previous chapters to VoIP troubleshooting. Although they might not have learned all the ways VoIP connections and calls can fail, students should be able to apply their understanding of packet switched networks and its potential faults to come up with reasonable suggestions for addressing VoIP problems.

Case Projects

Case Project 12-1
Some questions for SRSS to consider when evaluating a VoIP solution might include: * What advantages do you expect VoIP to bring to your organization? (Cost savings? Better efficiency? Higher quality or easier contact with clients?) * If you expect to reap cost savings by using VoIP, what are you currently paying for telephone services for all offices and workers and how does this compare to what it might cost to implement VoIP? * What is your current overall technology budget? * What equipment (e.g., servers, routers, and switches) do you already have that could also support VoIP? * How much technical support will you need to implement VoIP (in other words, does anyone currently on staff have the skills to install, configure, and maintain the system)? * Do you expect workers to use VoIP only while at the office, or also while on the road? * If you cannot afford a proprietary VoIP solution, are you prepared to install an open-source system, such as Asterisk?
For a social services agency, cost is usually the limiting factor in adopting any new program or technology, and so the key questions are any related to how much the organization can afford to purchase and support VoIP.

Case Project 12-2
For this project, students should research some of the most reliable, turnkey VoIP and Video-over-IP solutions available. Ease of use and management should be priorities when assessing systems, as should reliability and the capability for expansion. Students should be able to name every piece of hardware and software required for the system they choose. They should also obtain pricing (if necessary, requesting it from a vendor). Besides VoIP for SRSS staff, videoconferencing might be a good use of the grant money, which may cut travel time and costs and serve remote clients better.

Case Project 12-3
In this project, students should draw a WAN that includes videoconferencing equipment, including, at least, videorecording/broadcasting methods where speakers are located, video bridges, gateways, and video phones where necessary. Upon researching the widespread use of videoconferencing, students might determine that leasing a service with worldwide coverage would make more sense than trying to find individual videocasting facilities (for example, at a university), which would need to be leased separately, close to every speaker.