The following Glossary in no way covers all the new language and acronyms that are associated with VoIP technologies, but it may get you a step closer to understanding some of the jargon you may encounter.
Codec (Coder Decoder)
In VoIP it is a voice compression-decompression algorithm that defines the rate of speech compression, quality of decompressed speech and processing power requirements.
G.711 - This vocoder is used with PSTN lines. It is commonly called PCM (Pulse Code Modulation). There are two types of algorithm: u-law used in North America and Japan, and A-law used in the rest of the world. This vocoder algorithm produces a bit rate of 64 Kbits/second and has no silence suppression. This means silence is transmitted and occupies bandwidth.
G.723 - This vocoder is commonly used in VoIP gateways. It is called a Multi-rate Coder and it has two bit rates, 5.3 and 6.4 Kbits/second. This vocoder algorithm has silence suppression, meaning silence is not transmitted and does not occupy bandwidth.
G.726 - This vocoder frequently called ADPCM (Adaptive Differential Pulse Code Modulation) is used in the NACT IPAX gateway for the playback of voice messages such as authorisation code and destination number prompts. This vocoder algorithm can produce bit rates of 16, 24, 32, and 40 Kbits/second. The NACT IPAX voice prompts are recorded at 32 Kbits/second. This vocoder has no silence suppression, meaning silence is transmitted and occupies bandwidth.
G.727 - This vocoder oftentimes called Variable-Rate ADPCM is available in the NACT IPAX VoIP vocoder suite. This vocoder algorithm allows bit rates of 16-40 Kbits/second for sending and receiving voice. The bit rates can be variable sin each direction. It has no silence suppression.
G.728 - This vocoder sometimes known by the abbreviation LD-CELP (Low-Delay Code Excited Linear Prediction) is used in some VoIP gateways. It has a bit rate of 16 Kbits/second.
G.729 - This vocoder often known by the abbreviation CS-ACELP (Conjugate Structure Algebraic-Code Excited Linear Prediction) is used in many VoIP gateways. It has a bit rate of 8 Kbits/second. This vocoder algorithm has silence suppression meaning silence is not transmitted and does not occupy bandwidth.
DHCP: Dynamic Host Configuration Protocol
It is a communications protocol that lets network administrators centrally manage and automate the assignment of Internet Protocol (IP) addresses in an organisation's network. Using the Internet Protocol, each machine that can connect to the Internet needs a unique IP address, which is assigned when an Internet connection is created for a specific computer. Without DHCP the IP address must be entered manually at each computer in an organisation and a new IP address must be entered each time a computer moves to a new location on the network. DHCP lets a network administrator supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network.
DID: Direct Inward Dialing
The ability to make a telephone call directly to an internal extension without having to go through an operator.
DNS: Domain Name System
It resource record which specifies a regular expression based rewrite rule that, when applied to an existing string, will produce a new domain label or Uniform Resource Identifier (URI).
Firewall
A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented as hardware, software, or a combination of both. All messages entering or leaving pass through the firewall, which examines each message and blocks those that do not meet the security criteria specified on the firewall.
Gateway
In IP telephony a gateway is a network device that converts voice and fax calls in real time between public switched telephone networks (PSTN) and an IP network. The primary functions of an IP gateway include voice and fax compression/decompression, packetisation, call routing, and control signaling.
Hub
A hub is a communication device that distributes data to several devices in a network by re-broadcasting the data that has been received from one (or more) of the devices connected to it.
IVR: Interactive Voice Response
Is an automated software-based telephone information system that speaks to callers using a mix of fixed voice menus and real-time data accessed from databases. Callers interact with an IVR by making touch-tone keypad selections or speaking words or short phrases. IVR systems are used to route callers to specific personnel or departments, conduct polls or provide information, such as billing information or bank balances.
ISDN: Integrated Services Digital Network
This is a digital telephony and data-transport service offered by regional telephone carriers. ISDN involves the digitisation of a telephone network, which permits voice, data, text, graphics, music, video, and other source material to be transmitted over existing telephone wires.
IP Address:Internet Protocol
An IP address is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network. Any participating network device including routers, switches, computers, time-servers, printers, Internet fax machines, and some telephones have their own unique address.
An IP address acts as a locator for one IP device to find another to interact with.
Jitter
In VoIP jitter is the variation in the time between packets arriving caused by network congestion, timing drift, or route changes. A jitter buffer can be used to handle jitter.
Latency
In a network latency, a synonym for delay, is an expression of how much time it takes for a packet of data to get from one designated point to another. Latency is measured by sending a packet that is returned to the sender and the round-trip time is considered the latency.
NAT: Network Address Translation
NAT is a technique of transcribing network traffic through a router that involves re-writing the source and/or destination addresses of IP packets as they pass through. Most systems using NAT do this so multiple hosts on a private network can access the Internet using a single public IP address. Many network administrators find NAT a convenient technique and use it widely.
PPP: Point-to-Point Protocol
PPP is a connection oriented protocol that establishes a link between two communication devices that encapsulates data packets (such as Internet packets) for transfer between two communication points. PPP allows end users (end points) to setup a logical connection and transfer data between communication points regardless of the underlying physical connection (such as Ethernet, ATM, or ISDN).
Protocol
A protocol is a formalised set of rules that computers use to communicate. This strictly defines procedure and message formats allowing two or more systems to communicate over a transmission medium.
PSTN: Public Switched Telephone Network
The world's collection of interconnected public telephone networks, both commercial and government-owned.
Port
There are 2 kinds of Ports, Physical Port and Logical Port. A physical port is located on computer and telecommunication devices where you can physically connect to some other device, usually with a socket and plug of some kind. Logical port is a term used in programming. It is a logical connection place like on a router interface when you login you see SIP ports or RTP ports, Ports required by Blueface are UDP 5060-5061 for VoIP and UDP 10000-20000 for voice.
Packet
A technique for routing data through a network by encapsulating data in to packets. These packets are then labeled with addresses and routing information and forwarded until they reach their intended destination.
PRI: Primary Rate Interface
This term is always used in connection with ISDN as in "ISDN PRI". It refers to a digital circuit, such as a T1 or E1 that carries multiple calls and uses the ISDN signaling protocol.
P2P: Peer to Peer
This is a program that allows a computer to link to another computer via the Internet. Often information and data can be downloaded and exchanged.
PBX: Private Branch Exchange
It is a very small specialised switch. It permits any attached telephones to call each other using shorter numbers and requires the caller to select an "outside line" to make calls outside the switch. A VoIP based PBX is a very common device which can be hardware or a software at the user's end that manages calls and diverts.
RTP: Real-Time Transport Protocol
Commonly RTP is a packet based communication protocol that adds timing and sequence information to each packet to allow the reassembly of packets to reproduce real time audio and video information. RTP is a transport used in IP audio and video environments.
RJ11
RJ11 is a physical connector mostly used for terminating telephone wires.
RJ45
RJ45 is a physical connector commonly used for telephone and data communication systems.
SIP
SIP is a protocol designed to allow personal computers to place telephone calls on the Internet. It is a standard protocol for initiating an interactive user session that involves multimedia elements such as video, voice, chat and gaming.
STUN
STUN is a protocol for assisting devices behind a NAT firewall or router with their packet routing. STUN allows applications to discover the presence and types of NATs and firewalls between them and the public Internet.
Switch
A switch is a device that connects two separate data paths together. For example to connect two computers to one printer.
Trunk
Uploading information is used to describe transferring data from your computer to the Internet or another remote computer.
Tunnel
Tunneling is a way in which data is transferred between two networks securely. All the data being transferred is fragmented into smaller packets or frames and then passed through the tunnel.
UDP: User Datagram Protocol
The User Datagram Protocol is the IP protocol that delivers data in the same manner in which it was sent. For example if the sender transmits 20 bytes in a packet, they are delivered to the receiver as 20 bytes.
VPN: Virtual Private Network
This enables IP traffic to travel securely over a public TCP/IP network by encrypting all traffic from one network to another. A VPN uses "tunneling" to encrypt all information at the IP level.
