ACELP
Algebraic Code Excited Linear Prediction

ADPCM
Adaptive Differential Pulse Code Modulation

AMR-WB
Adaptive Multi Rate – WideBand

ATA
Analog Telephone Adaptor connects the conventional telephone to the Internet, converts the analog voice signals into IP packets, delivers dial tone and manages the call setup.

Broadband
High speed Internet connection, such as cable TV, DSL or dedicated telecom lines(T1/E1).

C7
Common Channel Signaling 7.

Cable modem
A device used to connect a computer to the high speed coaxial cable run by cable TV companies to provide access to the Internet.

CALEA
Communications Assistance for Law Enforcement Act.

Call agent
The intelligent and controlling entity in an MCGP based IP telephony network.

Call flow
The setup and tear down process and steps for a call to start till finish.

CB-WFQ
Class-Based Weighted Fair Queuing.

CDR
Call Detail Record.

CID
Caller Identification (ID).

Circuit switched network
The traditional telephone network used for making phone calls since 1878.

Codec
Compressor-Decompressor or enCOder/DECoder process.

Committed Access Rate (CAR)
A QoS feature.

Compression
The squeezing of data in a format that takes less space to store or less bandwidth to transmit.

Compression delay
The delay caused by the compression of data.

Congestion
The situation in which the traffic present on the network exceeds available network bandwidth/capacity.

CoS
Class of Service.

CPE
Customer Premises Equipment.

cRTP
Compressed Real Time Transport Protocol.

CS-ACLEP
Conjugate-Structure Algebraic-Code-Excited Linear-Prediction

Custom Queuing
A queuing method that allows a customer to reserve a percentage of bandwidth for specified protocols.

Data compression
The process to compress large data files into small files so that they use less bandwidth during transmission and less disk space when stored.

Decompression
Process by which the full data content of a compressed file is restored.

DiffServ
An architecture for implementing scalable service differentiation in the Internet for QoS.

DivX
A video codec used for internet, broadcast, and on storage media.

DPCM
Differential Pulse Code Modulation.

DSL modem
A device used to connect computers to the DSL line provided by a DSL operator to gain access to the Internet.

DTMF
Dual-Tone Multi Frequency.

Dynamic Jitter Buffer
Collects voice packets, stores them, and shifts them to the voice processor in evenly spaced intervals to reduce any distortion in the sound.

E&M (Ear and Mouth)
A type of supervisory line signaling.

E911
Enhanced 911; used for providing emergency service on cellular and Internet voice calls.

Emergency 911 calls
An emergency telephone number that handles all calls related to police, fire or medical emergencies in North America.

Fair Queuing
A scheduling scheme to allow several data flows to fairly share the link capacity.

FoIP
Fax over Internet Protocol.

Frame Relay Forum 12 (FRF.12)
A Frame Relay specification of fragmenting Frame Relay frames into smaller frames.

G.711
ITU-T specification of audio CODEC.

G.721
ITU-T specification of audio CODEC.

G.722
ITU-T specification of audio CODEC.

G.722.1
ITU-T specification of audio CODEC.

G.722.2
ITU-T specification of audio CODEC.

G.723
ITU-T specification of audio CODEC.

G.723.1
ITU-T specification of audio CODEC.

G.726
ITU-T specification of audio CODEC.

G.727
ITU-T specification of audio CODEC.

G.728
ITU-T specification of audio CODEC.

G.729
ITU-T specification of audio CODEC.

Gatekeeper
A device that translates network addresses and aliases to make connections via the H.323 protocol on a packet-switched network.

Gateway
A device that acts as an interface between two or more networks to connect dissimilar communications systems.

Generic Traffic Shaping (GTS)
A mechanism to control the traffic flow on a particular interface.

H.225.0
A protocol for call signaling, the media (audio and video), the stream packetization, media stream synchronization and control message formats.

H.235
For security in H.323 network.

H.239
For dual stream use in videoconferencing.

H.245
A control protocol for multimedia communication.

H.246
ITU-T specification for H.323/PSTN Interworking.

H.248
ITU-T standard for a centralized VOIP network. (Same as Megaco defined by IETF.)

H.261
Used primarily in older videoconferencing and video telephony products.

H.263
Used primarily for videoconferencing, video telephony, and internet video.

H.264
Also known as MPEG-4 Part 10, or AVC (for Advanced Video Coding).

H.323
An umbrella recommendation from the ITU-T that defines the protocols to provide audio-visual communication sessions on any packet network.

H.350
Directory Services Architecture for Multimedia Conferencing.

H.360
An architecture for end-to-end QoS control and signaling.

H.450
For supplementary services such as call waiting, call forwarding, etc.

H.460.x
Supplements in H.323.

H.501
Protocol for mobility management and intra/inter-domain communication in multimedia systems.

H.510
Mobility for H.323 multimedia systems.

Hairpin
To send a call back in the direction that it came from.

Hop off
Point at which a call transitions from H.323 to non-H.323, typically at a gateway.

iLBC
Internet Low Bitrate Vocoder.

Instant Messenging (IM)
A software that allows users to exchange messages in real time. For example, MSN Messenger, Yahoo! Messenger, etc.

Internet telephony
Technologies and services of using the Internet for voice and multimedia communications.

IntServ
An architecture which specifies the elements to guarantee quality of service (QoS) on networks.

IP
Inernet Protocol.

IP Centrex
Using IP-based network to provide centrex services such as call hold, call transfer, last number look-up and redial, call forward, three-way calling.

IP fragmentation
IP datagrams to be fragmented into pieces small enough to pass over a link with a smaller MTU than the original datagram size.

IP PBX
IP Private Branch Exchange. A telephone, data and video switching system, usually located on customer premises and belonging to the user.

IP phone
A device that converts voice into digital packets and vice versa to make phone calls over Internet possible.

IP telephony
Technologies and services for the two-way transmission of voice over IP network.

IPDC
IP Device Control (protocol).

IPDR
Internet Protocol Detail Record (protocol).

ISDN
Integrated Services Digital Network.

ITSP
Internet Telephony Service Provider.

Jitter
A momentary fluctuation in the transmission signal.

Lag
The extra time taken by a packet of data to travel from the source computer to the destination computer and back again.

Latency
The time that elapses between the initiation of a request for data and the start of the actual data transfer.

LDCELP
Low-Delay Code Excited Linear Prediction.

LPC
Linear-Predictive Codec.

LPCP
Lightweight Phone Control Protocol.

MCML PPP
Multi-Class Multilink Point-to-Point Protocol.

Media gateway (MG)
A translation unit between disparate telecommunications networks.

Media gateway controller (MGC)
A system used in MGCP/H.248/Megaco VoIP telephony architectures to control a number of Media Gateways.

Megaco
A IETF VOIP signaling protocol, same as H.248 of ITU-T.

MGCP
Media Gateway Control Protocol.

Modulation
To carring information on a signal by varying one or more of the signal's basic characteristics -- frequency, amplitude and phase.

MoIP
Modem over IP.

MOS
Mean Opinion Score, a numerical indication of the perceived quality of received media after compression and/or transmission.

MPEG-4 Part 10
Also known as H.264 or AVC, a video codec used for internet, broadcast, and on storage media.

MPEG-4 Part 2
Used for internet, broadcast, and on storage media.

MP-MLQ
Multi-Pulse, Multi-Level Quantization.

MTU
Maximum Transmission Unit.

NCS
Network-Based Call Signaling.

Net Phone
A net phone uses the Voice over IP technology to make voice calls.

Network convergence
The integration of all traffic types - voice, data and video solutions - onto a single IP network.

NGN
Next Generation Network.

OSP
Open Settlement Protocol.

Packet loss
The loss of data packets during transmission over a computer network.

Packet switched network
Networks that break messages into small packets, and route them across different channels to their destination where they are reassembled in their proper sequence.

PBX
Private Branch Exchange is an in-house telephone switching system.

PCM
Pulse Code Modulation.

Peer-to-Peer (P2P)
A form of computing where two or more than two users can communicate directly without a central control point.

Policy-based Routing
A technique used to make routing decisions based on policies set by the network administrator.

POTS
Plain Old Telephone Service.

PQ-CBWFQ
Priority Queuing - Class-Based Weighted Fair Queuing.

PRI
Primary Rate Interface, a type of ISDN interface.

Priority Queuing (PQ)
A queuing technique to give mission-critical traffic higher priority that less critical traffic.

Processor drain
A drop in the quality of VoIP phone service when a user opens several applications on his computer simultaneously.

Propogation delay
The time required for a signal to travel from one point to another.

Proxy server
Performs routing of a session invitations according to invitee's current location, authentication, accounting, etc.

PSTN
Public Switched Telephone Network, refers to the telephone system that transmits analog voice data.

Q.931
ISDN connection control protocol.

QoS
Quality of Service.

QSIG
Signaling standard for PBX.

RADIUS
Remote Authenticaion Dial-In User Service.

Random Early Detection (RED)
An active queue management algorithm. It is also a congestion avoidance algorithm.

RAS
Registration, Admission, Status (RAS), a management protocol between terminals and Gatekeepers in the H.323 network.

Redirect server
Receives a request and sends back a reply containing a list of the current location of a particular user.

Registrar server
Accepts REGISTER requests and places the information it receives in those requests into the location service for the domain in handles.

RSVP
Resource Reservation Protocol.

RTCP
Real Time Control Protocol.

RTP
Real Time Transport Protocol.

RTSP
Real Time Streaming Protocol

RUDP
Reliable User Datagram Protocol.

Sampling
A methodology used to measure the value of an analog signal at regular intervals, and encoding it into a digital format for phone services.

Sampling rate
The number of samples per second taken from a continuous (analog) signal to make a discrete(digital) signal.

SAP
Session Announcement Protocol.

SCCP
Skinny Client Control Protocol.

SCTP
Stream Control Transmission Protocol.

SDP
Session Description Protocol.

Servie Level Agreement (SLA)
A contract between a network service provider and a customer that specifies what services and quality the service provider will furnish.

Service provider
A business entity that provides a communication, storage or processing service for a fee.

SGCP
Simple Gateway Control Protocol.

Signaling gateway
A network component responsible for translating signaling messages between one medium (usually IP) and another (PSTN).

SIGTRAN
A family of protocols that provides reliable datagram service and user layer adaptations for SS7 and ISDN communications protocols.

SIP
Session Initiation Protocol, an IP telephony signaling protocol.

SIP phone
A telephone that uses the SIP (Session Initiation Protocol) standard to make a voice call over the Internet.

Skinny
Skinny Client Control Protocol.

Skype
A peer-to-peer Internet telephony company that leading the way voice calls are made by using VoIP technology.

Soft switch
A software application that is used to keep track of, monitor or regulate connections at the junction point between circuit and packet networks.

Softphone
A software application that is installed in the user’s PC enables voice calls over the Internet.

Softphone client
The software installed in the user’s computer to make calls over the Internet.

Speex
A free software speech codec.

SRTP
Secure Real-time Transport Protocol.

SS7
Signaling System number 7.

T.120
ITU-T specifcation for Real-time Conferencing.

T.38
ITU-T specification for Facsimile over IP.

TAPI
Telephony API.

ToS
Type of Service.

Traffic shaping
To control network traffic in order to optimize or guarantee performance, low latency, and/or bandwidth.

Unified Messaging (UM)
The integration of different streams of messages (e-mail, Fax, voice, video, etc.) into a single in-box, accessible from a variety of different devices.

User Agents
A software program installed in a user’s terminal or an IP phone to initiate and terminate phone calls.

V.150
ITU-T specification for Modem over IP.

Voice chat
An application that enables two or more individuals to carry on a verbal conversation (audio conference) over the Internet.

Voice over IP (VOIP)
The technology that is used to transmit voice over the Internet.

Voicemail
A telephone messaging system that digitizes the analog voice signals and stores them on disk or flash memory in a central computer.

VOIP Gateway
A device provides the conversion interface between the PSTN and an IP network for voice and fax calls.

VOIP PBX
Voice over Internet Protocol Private Branch eXchange.

VOIP Phone
A device that uses the IP network to route voice calls by converting the voice data into IP packets and vice versa.

VOIP services
Services that use the IP network to move voice data.

Web phone
A device that allows users to make voice calls over the Internet.

WFQ
Weighted Fair Queuing, a packet scheduling technique allowing guaranteed bandwidth services.

WiFi phone
A device that enables users to make phone calls from WiFi network environments.

WMV
Windows Media Video.

WRED
Weighted Random Early Drop/Detect.

X264
A GPL-licensed implementation of H.264 encoding standard.

ZRTP
An extension to RTP which describes a method of Diffie-Hellman key agreement for SRTP.