RADVISION术语表

Glossary (D)

# - A - B - C - D - E - F - G - H - I - J - K - L - M - N
O- P - Q - R - S - T - U - V - W - X - Y - Z

D CHANNEL
The data signaling channel of an ISDN line. This channel is used to carry call control messages between the ISDN terminal and the public switch.

DEFERRED DELIVERY MESSAGING
A type of IMS Messaging service by which the sender expects the network to deliver the message as soon as the recipient becomes available.

DELAY
The time taken for a signal to pass through a video conference from the sending station to the receiving station.

DES (DATA ENCRYPTION STANDARD)
A cryptography method that makes it impossible for anyone without the decryption key to restore the data to its unscrambled form. DES is now considered to be insecure for many applications. This is chiefly due to the 56-bit key size being too small; DES keys have been broken in less than 24 hours.

DESKTOP VIDEO CONFERENCING
Video conferencing on a personal computer. Most appropriate for small groups or individuals. Many desktop video conferencing systems support document sharing or data collaboration.

DEVICE ADDRESS
The unique network address of a device, assigned by a carrier and following the format defined by an international standard such as E.164 for MSISDN addresses, X.121 for X.25 addresses or RFC 791 for IP addresses. An address uniquely identifies the sending and/or receiving device.

DEVICE PROFILE
Information describing the capabilities of the device.

DHCP (DYNAMIC HOST CONFIGURATION PROTOCOL)
In a DHCP environment, IP policy is dynamic. This means that a terminal does not have a constant IP address. Management keys for identifying endpoints in a DHCP environment are the alias name or phone number of an endpoint.

DIAL PLAN
In traditional telephony systems, a dial plan is a front end system that allows users to call each other by dialing a number on a telephone. In voice and video conferencing over IP, a dial plan is a system that allows participants in point-to-point or multipoint conferences to call each other or join conferences.

DIAMETER
An AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. The basic concept is to provide a base protocol that can be extended in order to provide AAA services to new access technologies. It is the AAA protocol chosen for the IMS environment.

DID (DIRECT INWARD DIALING)
A method in which incoming calls are routed directly to endpoints on the LAN, without operator intervention.

DLNA (DIGITAL LIVING NETWORK ALLIANCE)
A global cross-industry organization of leading consumer electronics, computing industry and mobile device companies that share a vision of a wired and wireless interoperable network where digital content, such as music and videos can be seamlessly shared through personal computers (PCs), consumer electronics (CE) and mobile devices in and beyond the home.

DNS (DOMAIN NAME SERVER)
On TCP/IP networks, DNS converts the domain name (URL) of a host computer into a numeric IP address using the following format: xxx.xxx.xxx.xxx.

DOCUMENT SHARING
A video conferencing feature that enables multiple participants to view and edit the same computer document.

DOWNLINK
Unidirectional radio link for the transmission of signals from a UTRAN access point to the UE. Also the direction from a Network to the UE, in general.

DOWNSPEEDING
The ability of a Gateway to maintain an ISDN video call by reconnecting the call at a lower rate when one of the B channels is lost. Downspeeding contributes to a higher percentage of call completion on the network.

DSP (DIGITAL SIGNAL PROCESSING)
The study of signals in a digital representation and the processing methods of these signals. The goal of DSP is usually to measure or filter continuous real-world analog signals. The algorithms required for DSP are sometimes performed using specialized computers, which use specialized microprocessors called digital signal processors. These process signals in real time and are generally purpose-designed ASICs.

DTMF (DUAL TONE MULTI-FREQUENCY)
Also called touch-tone dialing. The tones that are heard when you press the buttons on a touch-tone telephone.

DVB (DIGITAL VIDEO BROADCAST)
A suite of internationally accepted, open standards for digital television maintained by the DVB Project, an industry consortium and published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU).