9.2 Voice over IP (VoIP)

Which switch features are typically used with VoIP? (Select two.)

1. VLAN 2. PoE When configuring Voice over IP (VoIP), switches with Power over Ethernet (PoE) capabilities provide power to the VoIP phone through an Ethernet cable, the same cable that is used for transmitting data signals. Virtual LANs (VLANs) are often used to distinguish voice traffic from data traffic so that Quality of Service (QoS) measures can be applied to traffic that is part of the voice VLAN.

What are other names for a VoIP server? (Select two.)

1. VoIP PBX 2. IP-PBX A VoIP server is also known as a VoIP PBX or an IP-PBX since a VoIP server provides many of the functions of a traditional phone system PBX.

When would you consider changing the codec used in your VoIP system? (Select two.)

1. When VoIP data consumes too large a portion of your network bandwidth. 2. When sound quality is poor. A special algorithm called a codec compresses VoIP data to reduce bandwidth consumption. A codec determines the sound quality of the VoIP call and the amount of bandwidth that it will require.

What is a soft phone?

A software application that runs on a computer or other device that accesses a VoIP server to make real-time phone calls. A soft phone is a software application that is installed on a computing device such as a computer or a handheld device.

Your company uses VoIP for phone calls. Recently, employees have been complaining about phone calls with unusual sound effects. Which type of problem is occurring on the VoIP system?

Jitter. Because VoIP transmits call data using IP packets over a packet-switched network, VoIP is susceptible to the following problems: Latency occurs when data takes a long time to arrive at the receiving device. Delays cause long pauses between speaking and receiving and can result in callers continually interrupting each other. Jitter is a variation in the delay of individual packets. Jitter causes strange sound effects as the delay of packets fluctuates. Packet loss occurs when packets do not arrive at all. Packet loss causes drop-outs in the conversation. Echo occurs when you hear your own voice in the telephone receiver while you are talking. Excessive delay can cause unacceptable levels of echo

You are on a phone call using VoIP. You notice that it takes several seconds for the person on the other end to respond to questions you ask. Which type of problem is occurring?

Latency. Because VoIP transmits call data using IP packets over a packet-switched network, VoIP is susceptible to the following problems: Delay (or latency), which occurs when data takes a long time to arrive at the receiving device. Delays cause long pauses between speaking and receiving and can result in callers continually interrupting each other. International standards call for a delay of 150 milliseconds or less. Jitter, which is a variation in the delay of individual packets. Jitter causes strange sound effects as the delay of packets fluctuates. Packet loss, which occurs when packets do not arrive at all. Packet loss causes dropouts in the conversation. Echo, which occurs when you hear your own voice in the telephone receiver while you are talking. Excessive delay can cause unacceptable levels of echo.

What is one benefit of placing VoIP gateways in geographically separated branch offices that have an existing WAN connection?

Long-distance PSTN charges can be reduced by switching VoIP calls to the PSTN in locations where only local call charges would be incurred. VoIP gateways convert voice and fax calls between the PSTN and an IP network. A WAN connection can carry VoIP calls from a distant location to a geographically separated branch office. A VoIP gateway located at the branch office can switch the call to the PSTN, where only local phone charges would be incurred.

Which of the following features is used with digital IP phones to supply power through a switch port?

PoE. Power over Ethernet (PoE) supplies power to end devices through the RJ45 Ethernet switch port. Power to the phone is carried on unused wires within the drop cables.

How can QoS be configured so that large data transfers will not block VoIP calls by using too much network bandwidth?

QoS can be configured on network devices to give priority to VoIP traffic. Network devices can examine the type of service or precedence bits in the header of an IP packet to determine the type of traffic. QoS settings can be configured on a network devices to give VoIP traffic priority over normal computer traffic.

Which of the following protocols is used by VoIP to set up, maintain, and terminate a phone call?

SIP. The session initiation protocol (SIP) is used to set up, maintain, tear down, and redirect the call. The real-time transport protocol (RTP) contains the actual voice data.

Which of the following protocols is an open source protocol used by most manufacturers of VoIP systems?

Session initiation protocol (SIP). The session initiation protocol (SIP) is one of the protocols used during the call control process of multimedia communications, such as a VoIP call. SIP is used to set up, maintain, and tear down multimedia communications. SIP rides on top of the TCP, UDP, and SCTP transport layer protocols.

Upper management has asked you if there is a way to integrate phone calls, emails, and instant messaging into a single platform. Which of the following systems should you recommend?

Unified communication Unified communications (UC) integrates multiple types of communications into a single system. UC systems can integrate the following real-time communications: Voice calls Audio conferencing Video conferencing (VTC) Desktop sharing Instant messaging

Which VoIP device helps establish the connection between two VoIP phones?

VoIP server. A VoIP server helps establish the connection between two VoIP phones. Once the connection is established, the two phones communicate directly with each other.