Media5 Mediatrix 4104, Справочное руководство

Страница: 441 / 466

G.711 Reference Manual (SIP Version)
Mediatrix 4104 419
G.711
ITU-T recommendation for an algorithm designed to transmit and receive A-law PCM (Pulse Code Modulation)
voice at digital bit rates of 48 kbps, 56 kbps, and 64 kbps. It is used for digital telephone sets on digital PBX
and ISDN channels.
G.723.1
A codec that provides the greatest compression, 5.3 kbps or 6.3 kbps; typically specified for multimedia
applications such as H.323 videoconferencing.
G.726
Nn implementation of ITU-T G.726 standard for conversion linear or A-law or µ-law PCM to and from a 40, 32,
24 or 16 kbit/s channel.
G.729
A codec that provides near toll quality at a low delay which uses compression to 8 kbps (8:1 compression rate).
Gateway
A device linking two different types of networks that use different protocols (for example, between the packet
network and the Public Switched Telephone Network).
Impedance
Impedance is the apparent resistance, in an electric circuit, to the flow of an alternating current, analogous to
the actual electrical resistance to a direct current, being the ratio of electromotive force to the current.
International Telecommunication Union (ITU)
Organization based in Geneva, Switzerland, that is the most important telecom standards-setting body in the
world.
Internet-Drafts
Internet-Drafts are working documents of the IETF, its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts.
Internet Protocol (IP)
A standard describing software that keeps track of the Internet’s addresses for different nodes, routes outgoing
messages, and recognizes incoming messages.
Jitter
A distortion caused by the variation of a signal from its references which can cause data transmission errors,
particularly at high speeds.
Layer 2
Layer 2 refers to the Data Link Layer of the commonly-referenced multilayered communication model, Open
Systems Interconnection (OSI). The Data Link Layer is concerned with moving data across the physical links
in the network.
The Data-Link Layer contains two sublayers that are described in the IEEE-802 LAN standards:

Media Access Control (MAC)

Logical Link Control (LLC)
Layer 3
Layer 3 refers to the Network layer of the commonly-referenced multilayered communication model, Open
Systems Interconnection (OSI). The Network Layer is concerned with knowing the address of the
neighbouring nodes in the network, selecting routes and quality of service, and recognizing and forwarding to
the transport layer incoming messages for local host domains.