VoIP Flashcards
What is a Voice over IP Telephone
a Voice over IP telephone is more of a computer than a telephone. It has to be a LAN device, it has to be an IP device, it has to have a codec for digitizing the speech and compressing it, it has to run protocols like SIP to set up phone calls, it might have to do authentication to register with a Soft Switch, there are a lot of pieces of software that is running inside of that telephone.
What “computer” functions must a VoIP phone perform?
Since it is VoIP, this computer that looks like a telephone also has to have a IP protocol stack. It also has to have a DHCP client (Dynamic Host Configuration Protocol). This is a little software program that lets the phone go off over the LAN to a DHCP Server and get an IP address assigned to it. It also has to support protocols like UDP.
Short answer: IP, DHCP and LAN functions
Which of the following are the minimum requirements on a VoIP telephone?
The G.711 Codec & SIP Client
What component produces coded digitized speech?
Codec
How are IP packets moved from one router to another?
Carried in Ethernet MAC frames (Media Access Control)
How much speech is typically contained in an IP packet?
20 Milliseconds
What is the difference between SIP and a softswitch?
SIP is a Protocol. A softswitch is a call management system
What is the main purpose of a SIP?
To communicate the IP address of telephones to each other
What is a key attribute of a video server?
Movies stored in Random Access Memory so multiple people can watch at different start times
What protocol is between RTP (Real-Time Transport Protocol) and IP (Internet Protocol)?
UDP (User Datagram Protocol)
What does RTP (Real-Time Transport Protocol) do?
Adds a time stamp
What does “IP dial tone” mean?
A service that allows you to send an IP packet to any destination on the network, like telephone calls.
The telephone network and the internet being the same thing.
Telephone service becomes a helper application to set up a Voice over IP phone call.
Once there is IP dial tone, what happens to the World Wide Web?
It is simply a helper application DNS (Domain Name Server) to look up web server addresses
What technique is first used to represent speech inside a telephone?
Analog
What is a LAN (Local Area Network)?
Connects IP telephones to a router in-building
Which of the following is a function of a gateway?
Convert between DS0 (Digital Service Level 0) and RTP/IP
What is a media server?
Video server, Web server, Email server
what is a WAN (Wide Area Network)?
Connects to buildings
Which of the following does computer-computer VoIP over the internet provide?
Free calling
What performs the voice digitization and reconstruction function when doing computer to computer VoIP over the internet?
The sound card in the computer
What part of the network from calling party to called party does the VSP (Voice over IP Service Provider) provide?
Internet to LEC (Local Exchange Carrier)
What two essential functions does the VSP provide for internet to phone VoIP?
Gateway and softswitch
Why is phone to phone over the internet service cheaper than POTS?
Avoids switched access charges at the originating end
Avoids fees and taxes leveled on POTS
Service provider is not providing the long-distance network
What is a managed IP network?
An IP packet communication service with Service Level Agreements backing it up, i.e. guaranteed network quality
