AT-TQ2403 Management Software User's Guide

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transnational authorities such as the Federal Communications Commission (FCC), the European Telecommunications Standards Institute (ETSI), the Korean Communications Commission, or the Telecom Engineering Center (TELEC).

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is a low-level network arbitration/ contention protocol. A station listens to the media and attempts to transmit a packet when the channel is quiet. When it detects that the channel is idle, the station transmits the packet. If it detects that the channel is busy, the station waits a random amount of time and then attempts to access the media again.

CSMA/CA is the basis of the IEEE 802.11e Distributed Control Function (DCF). See also RTS and CTS.

The CSMA/CA protocol used by 802.11 networks is a variation on CSMA/CD (used by Ethernet networks). In CSMA/CD the emphasis is on collision detection whereas with CSMA/CA the emphasis is on collision avoidance.

CTS

A clear to send (CTS) message is a signal sent by an IEEE 802.11 client station in response to a request to send (RTS) message. The CTS message indicates that the channel is clear for the sender of the RTS message to begin data transfer. The other stations will wait to keep the air waves clear. This message is a part of the IEEE 802.11 CSMA/CA protocol. (See also RTS.)

D

DCF

The Distribution Control Function is a component of the IEEE 802.11e Quality of Service (QoS) technology standard. The DCF coordinates channel access among multiple stations on a wireless network by controlling wait times for channel access. Wait times are determined by a random backoff timer which is configurable by defining minimum and maximum contention windows. See also EDCA.

DHCP

The Dynamic Host Configuration Protocol (DHCP) is a protocol specifying how a central server can dynamically provide network configuration information to clients. A DHCP server "offers" a "lease" (for a pre-configured period of time—see Lease Time) to the client system. The information supplied includes the client's IP addresses and netmask plus the address of its DNS servers and Gateway.

DNS

The Domain Name Service (DNS) is a general-purpose query service used for translating fully-qualified names into Internet addresses. A fully-qualified name consists of the hostname of a system plus its domain name. For example, www is the host name of a Web server and www.alliedtelesis.com is the fully-qualified name of that server. DNS translates the domain name www.alliedtelesis.com to some IP address, for example 66.93.138.219.

A domain name identifies one or more IP addresses. Conversely, an IP address may map to more than one domain name.

A domain name has a suffix that indicates which top level domain (TLD) it belongs to. Every country has its own top-level domain, for example .de for Germany, .fr for France, .jp for Japan, .tw for Taiwan, .uk for the United Kingdom, .us for the U.S.A., and so on. There are also .com for commercial bodies, .edu for educational institutions, .net for network operators, and .org for other organizations as well as .gov for the U. S. government and .mil for its armed services.

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