ADSL/USB Modem by Multi-Tech Systems, Inc.
3
Chapter 1: Overview
About ADSL
Asymmetric Digital Subscriber Line (ADSL) technology provides high-speed data access
across regular phone lines (copper wires) by making use of previously unused frequency
bandwidth above the voice band. By placing the ADSL signal above the frequency of the
voice signal, ADSL service is able to coexist on the same line with your telephone service.
ADSL is asymmetric in the sense that it provides a higher data rate in the downstream
(receive) direction than in the upstream (transmit) direction. Asymmetric operation is ideal for
typical home and small office use where files and information are downloaded more
frequently than uploaded.
There are several standard types of ADSL modulation techniques including Discrete
Multitone (DMT) and Carrierless Amplitude and Phase (CAP). The MTD100U Modem
supports the following DSL standards: ANSI T1.413 Issue 2, ITU G.992.1 (G.DMT), and ITU
G.992.2 (G.lite).
Protocol and Device Driver Selection
The MTD100U Modem can be easily connected to a USB port on the PC via a standard USB
cable. The MTD100U Modem is fully software upgradable so that new features and updates
may be added by simply loading a new version of the device driver onto your PC.
ADSL modems employ ATM (Asynchronous Transfer Mode) framing. ATM is a protocol that
divides packets into small fixed sized cells for rapid transmission over high-speed networks.
The ATM protocol allows various types of traffic (e.g. data, voice, and video) to be securely
and efficiently carried over the same network. ATM is being widely deployed by
telecommunications carriers in their backbone networks. Two types of ATM connections are
possible, PVC (Permanent Virtual Circuit) and SVC (Switch Virtual Circuit).
Several different protocols are used on top of ATM. The protocol required in your
configuration depends on the equipment deployed by your DSL service provider. There are
several possibilities:
1.
Point to Point Protocol (PPP) Over ATM (RFC 2364) - PPP provides session setup,
user authentication (login), and encapsulation for upper layer protocols such as IP
(Internet Protocol). The use of PPP makes the modem appear as a dial modem to
the operating system. Dial-Up Networking is used to establish a connection. PPP is
supported by either the WAN (Wide Area Network) driver, or the ATM driver.
2.
Bridged/Routed Ethernet/IP over ATM (RFC 1483) – This protocol makes the modem
appear as a local area network (LAN) device to the operating system.
3.
RFC 1577 – this is another local area network like protocol for IP address and ATM
address mapping.
Summary of Contents for MTD100U
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