Acer ADSL Surf USB Modem - Manual (Page 8)

Installation Guide and User Manual
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 Multi-tone
(DMT) and Carrier-less Amplitude and Phase (CAP). The Acer ADSL Surf USB modem is capable
of supporting the following DSL standards: ITU G.992.1 (G.DMT) (Annex A ,Annex B), ITU
G.992.2 (G.LITE), ANSI T1.413 Issue 2 and ETSI TR328 .
Protocol and Device Driver
The Acer ADSL Surf USB Modem can be easily connected to a USB port on the PC via a
standard USB cable. The Acer ADSL Surf USB 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.