Installation guide

8
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 Amigo USB ADSL Modem is capable of supporting 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 Amigo USB ADSL Modem can be easily connected to a USB port on the PC via a standard USB cable.
The Amigo USB ADSL Modem is fully software upgradeable 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 type of ATM connections are possible, PVC (Permanent Virtual Circuit) and SVC (Switched 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.
Two types of device drivers are provided for the Amigo ADSL USB modem, WAN & LAN. Note that all
two drivers support ATM protocol. The proper choice of driver depends on the combination of Windows
operating system and protocol.