Motorola AL 200 Installationshandbuch - Seite 42

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Media Access Control

Address (MAC)

Media Access Control

(MAC) sublayer

MHz

modem registration

network driver

network layer

packet data

PING

physical layer (PHY)

Physical Media

Dependent (PMD)

Sublayer

piggybacking

Quadrature Amplitude

Modulation (QAM)

Glossary-4

The hardware address usually "burned in" on a ROM for any device connected

to the network. Ethernet cards in the subscriber PC have a MAC address. The

cable modem and the network interface card on a CMTS have MAC addresses.

The MAC address is used by the link layer protocol to forward packets "one

hop at a time" between the host and the first router and between the first router

and the next router and so on through the network until the packet arrives at its

final destination. In contrast, an IP address is a "source" to "destination"

address. It does not include all the intermediate hops.

The part of the data link layer that supports topology-dependent functions and

uses the services of the physical layer to provide services to the logical link

control (LLC) sublayer.

Mega Hertz. A measure of radio frequency - millions of cycles per second.

The process by which a cable modem makes itself known to a CMTS. The

modem configuration and authorization are verified and the COS is negotiated.

A file packaged with the Ethernet card that connects the card to the PC

communications software.

Layer 3 in the Open System Interconnection (OSI) architecture. This layer

provides services to establish a path between open systems.

Each IP datagram consists of one or more packets. A packet has a header that

contains the source address and a destination address for routing (and other

housekeeping information). Since both the header and the data area can vary in

length, an IP datagram itself is variable in length.

A program that tests host reachability by using the Internet Control Message

Protocol (ICMP) echo request and waiting for a reply. It is initiated and

verified from an IP device.

Layer 1 in the Open System Interconnection (OSI) architecture. It is the layer

that provides services to transmit bits or groups of bits over a transmission link

between open systems. It includes the electrical, mechanical, and handshaking

procedures.

A sublayer of the physical layer that transmits bits or groups of bits over

particular types of transmission links between open systems. It entails the

electrical, mechanical, and handshaking procedures.

A process that occurs when a modem transmits data and requests additional

bandwidth at the same time.

Modulation scheme that uses both amplitude and phase modulation to encode

multiple bits of data in one signaling element, thus achieving higher data

transfer rates than just amplitude or phase modulation alone.

However, the signal is more prone to errors caused by noise and so requires a

better quality transmission circuit than QPSK (lower noise and therefore higher

Carrier to Noise Ratio (CNR) value).