688 Appendix A: Answers to Review Questions
18
What product has Cisco released that envelops the total VoIP solution?
Call Manager.
19
What is a key switch?
A key switch allows multiple phones to share a common pool of external phone lines.
20
What is a PBX?
PBX allows interoffice communications and provides connectivity to the PSTN for
medium to large offices. PBXs are common in offices with more than 25 users.
21
What is a tandem switch?
A tandem switch is a device that accepts all calls and reroutes them to another destination.
Tandem switches are often located at the central office or at the headquarters site to reroute
calls made from site to site.
22
List three major functions of a voice over data network.
Signaling, addressing, routing.
23
What is the first step in establishing connectivity between a router and a phone switch?
Ensuring hardware and signaling compatibility.
24
True or false: VoFR and VoATM allow tandem call routing. VoIP does not.
True. VoIP requires the configuration of an H.323 gateway.
25
What feature automatically dials a predetermined number when a user goes off-hook?
Private Line Automatic Ring-Down (PLAR).
26
List one business requirement that would be satisfied by designing a voice over data
network.
Cost savings.
27
Define jitter.
Jitter is caused when packets arrive at different rates due to changes in the flow of network
traffic.
28
List some metrics that will define success on the voice over data design project.
Cost-effectiveness, functionality, scalability, manageability, interoperability.
29
What is the name of the signaling standard that is used to perform out-of-band signaling
in the PSTN?
Signaling System 7 (SS7).
87200333.book Page 688 Wednesday, August 22, 2001 1:41 PM