Glossary

Aliases
Alternative identification strings for an IP address.

B-ISDN
Broadband – ISDN. Enables telecommunications and video conferencing data to be transmitted over optical fiber at high speeds.

BRI
Basic Rate Interface to an ISDN network. A BRI line has two 64Kbps B channels that
transmit the data and one 16Kbps D channel that is used for call setup and control signaling.

Circuit-switched
The temporary connection of two or more communications channels. Users have full use of the circuit until the connection is terminated. ISDN is a circuit switched network.

CODEC
Coder/Decoder is a device that changes audio and video from analog to digital and then compresses the information for transmission. At the other end the signal is decompressed and decoded back into analog for viewing and listening on a monitor. This occurs in real time.

CTM
Click To Meet™. First Virtual Communications, Inc., product that combines a directory service for H.320, H.321, and H.323 endpoints in a multimedia environment.

Default extension
Any endpoint on the network that has been defined as an alternative destination on the network for incoming calls routed by the Gateway.

DID
Direct Inward Dialing is a method in which incoming calls are routed directly to endpoints on the LAN, without operator intervention.

DSCP
Differential Services Code Point is a service that helps to classify or differentiate traffic. This is done by setting the three MSBs of the Type of Service byte in the IP header. The router than prioritizes the packet according to how the precedence bit is set.

DTMF
Dual Tone Multi-Frequency signals are the type of audio signals used in telephony for tone dialing.

E.164
An International Technology Union recommendation for telephone numbering. In short, a telephone numbering scheme allowing up to 15 digits in the number scheme.

Endpoint
An H.323 terminal, gateway, or Multipoint Controller Unit (MCU). An endpoint can call or be called and it can generate or end information streams.

FLRQ
Forwarded Location Request. A location request that is passed from router to router until a gatekeeper is found at a specified IP address.

Gatekeeper
The gatekeeper is an H.323 entity that provides address resolution, access control, and other services to endpoints on an H.323 network.

Gateway
The gateway is a device that allows H.320 switched endpoint devices to be converted to digital H.323 endpoint devices for cross communication between protocols.

H.320
The ITU standard for video conferencing over digital networks such as ISDN.

H.321
The ITU standard for adaptation of H.320 video conferencing over digital networks such as B-ISDN.

H.323
The ITU standard for video conferencing over packet switched networks such as LANs and the Internet.

IP address
The unique address of a computer attached to a TCP/IP network. IP addresses are 32 bits long where each octet is represented in decimal and is separated by dots.

IP network
A network that uses the TCP/IP protocol.

ISDN
Integrated Services Digital Network. ISDN is an entirely digital telephone network that allows both data and voice communication over the same line. ISDN replaces the old analog local loop and operates at significantly faster speeds than the traditional telephone service.

IVR
Interactive Voice Response is a two-stage incoming call routing method supported by the Gateway. It enables Direct Inward Dialing to a LAN terminal even when the ISDN lines do not have multiple numbers allowing direct dialing to an endpoint.

LAN
Local Area Network. A network of connected computers covering a small geographic area such as a building or a campus.

LDAP
Lightweight Directory Access Protocol. A directory service that has many front-end applications for ease of use to find information on people. This service is not designed for multimedia applications.

LRQ
A signal sent out by an endpoint to a gatekeeper at a specified IP address.

MCU
Multipoint Controller Unit. H.323 endpoints that allow multipoint conferences to take place on the LAN.

NANP
North American Numbering Plan. It assigns area codes and sets rules for calls to be routed across North America. Lockheed Martin currently administers the NANP. In the context of this paper, NANP refers to a unique E.164 number accessible from the Public Switched Telephone Network (PSTN) using Direct Inward Dialing (DID).

Packet-switched
Networks that break up a message into smaller packets before switching the packets to their required destination. Each packet contains a destination address so all packets in a single message do not have to travel by the same path. The destination computer reassembles the packets back into their proper sequence.

PBX
Private Branch Exchange. A private telephone switching system in an organization that interconnects telephone extensions to each other and to the public telephone network.

PRI
Primary Rate Interface to an ISDN network. In the U.S., a PRI line provides 23B channels and one 64Kbps D channel (23B+D), which is equivalent to a T1 line and in Europe, a PRI line provides 30B channels and 1D channel (30B+D), equivalent to an E1 line.

PSTN
Public Switched Telephone Network. The worldwide telephone network.

RAS
Registration Admission Status protocol. The communication protocol used to convey registration, admission, and status messages between H.323 endpoints and the gatekeeper.

RED
Random Early Detection is a service that tells the router to slow down transmission of packets until all of the packets have reached their destination. During this process, some packets may be dropped. The router resumes speed of transmission after it senses job has reached its destination.

Room system
H.320 based legacy video conferencing stations. They are called room systems because they are usually large monitors with a wide-angle camera and served groups of people who meet in a room and conference with other similar groups at remote locations.

RSVP
Resource Reservation Protocol (RSVP) has been described by some to be the Nirvana to IP routing. At this time, RSVP is being actively developed but is not ready for deployment on core networks.

Telephony
The science of transmitting voice and/or video over a greater distance than you could do by shouting.

T.120
ITU standard for the transmission of data sharing applications during a video conferencing session.

TCS4
A Direct Inward Dialing routing method for H.320 calls supported by a gateway. This method requires support by the H.320 device performing the dialing.

Transcoding
The ability of a device to convert between one protocol and another. All aspects ranging from audio and video to control signaling are converted.

V.35
The V.35 is a serial interface used to connect Data Terminal Equipment and Data Circuit Terminating Equipment (DTE/DCE).
VoIP
Voice over IP is the ability to make telephone calls over IP based data networks with suitable quality of service.

WAN
Wide Area Network. A communications network over a wide geographic area.

WRED
Weighted Random Early Detection is Cisco Systems version of Random Early Detection. It is used to prioritize traffic while telling the router to slow down the transmission of packets until all of the packets have reached their destination.

Zone
In H.323 networks, a collection of terminals, gateways, and MCUs managed by a single gatekeeper. A zone must include at least one terminal and may include several LAN segments connected by routers.