TestOut Network Pro: 9.2 Voice over IP (VoIP)
How is a VoIP gateway used?
A VoIP gateway converts voice and fax calls between the PSTN and your IP network in real time. -VoIP gateways are generally smaller, less costly, and more specialized than VoIP servers. -VoIP gateway can be placed in geographically separated branch offices to save long-distance PSTN charges. -A call from the main office switched through the PSTN to a distant external phone would incur long distance charges. -A call from the main office traveling over an existing WAN to a VoIP gateway and then switched through the local PSTN to the same distant external phone would incur only local PSTN charges.
What is the function of a codec?
A codec is a special algorithm that compresses VoIP data to reduce bandwidth consumption. -A codec compresses the data on the sending end and decompresses the data on the receiving end. -A codec determines the sound quality of the VoIP call and the amount of bandwidth that it will require: -A codec that preserves sound quality may require a large amount of bandwidth to transmit. -A codec that requires less bandwidth may have poor sound quality.
What is jitter? How does it affect VoIP calls?
Jitter is a variation in the delay or latency or latency of received packets. Latency going up and down during a call can cause unusual sound effects (minor pauses, jumps, choppiness).
What happens if there is too much latency in a VoIP call?
Network latency is how long it takes for a packet of data to get from one point to another. Too much latency causes VoIP callers to talk over each other.
Why is quality of service (QoS) important for VoIP?
Quality of Service (QoS) can assign priority depending on the type of network traffic. -Network devices like switches and routers can examine the type of service bits and precedence bits in the header of an IP packet to determine the type of traffic. -QoS settings on network devices can be configured to give priority to VoIP traffic.
What are the functions of a VoIP server? What are other names for a VoIP server?
The heart of any VoIP system is the VoIP server, also known as a VoIP PBX or IP-PBX. -The main role of a VoIP server is to provide a switching mechanism to connect internal calls between VoIP endpoints. -VoIP servers also provide a switching mechanism to connect calls between internal VoIP endpoints and shared external public telephone network (PSTN) trunk lines. -VoIP servers connect to the network like other servers. -VoIP servers can also connect to PSTN trunk lines. -VoIP servers maintain user accounts: -Accounts map phone extension numbers to VoIP endpoints. -Accounts have usernames and passwords to provide authentication and security. -VoIP servers provide many of the functions a PBX: -Call waiting -Call transfer -Conferencing -Voice mail -Good VoIP servers have internal POTS ports that interface with other devices, such as fax machines that require an analog signal.
What is the difference between a hard VoIP phone and a soft VoIP phone?
The standard VoIP phone is a hard phone. Hard phones: -Have the look and feel of a traditional phone with a base and a handset. -Are really computers that are built to look and operate like phones. -Are connected to a network, just like any other computer. -Can be configured using a web browser connected to their web page interface. A soft phone: -Is a software application that is installed on a computing device like a computer or a handheld device. -Allows access to the VoIP server for real time audio communication.
What is the most common open source VoIP protocol?
VoIP uses protocols that reside on top of transport layers like TCP, UDP, and SCTP to assemble and distribute VoIP data throughout your network.The most common open source VoIP protocol is the session initiation protocol (SIP). -Most major manufacturers make SIP-compatible phones and phone systems. -Smaller manufacturers almost exclusively use SIP.
