Adsl Technologies; Adsl2 And Adsl2+: Enhancing Transmission Speeds - HP ProCurve Secure 7000dl Series Basic Management And Configuration Manual

With asymmetric DSL technologies, the transmission speed for downstream
is higher than the transmission speed for upstream. This makes asymmetric
DSL technologies ideal for Internet use because users typically download
more data from the Internet than they upload. Asymmetric DSL technologies
are also well-suited for video-on-demand or high-definition television (HDTV).

ADSL Technologies

Asymmetric DSL (ADSL) has emerged as one of the most widely used DSL
technologies. ADSL provides an end-to-end digital connection between the
source device and the destination device. Like an E1- or T1-carrier line, ADSL
is a leased private line and is always available.
ADSL service is usually provided through a partnership between an Internet
service provider (ISP) and a public carrier. (The public carrier is frequently
called the ADSL service provider.) The ISP provides the connection to the
Internet, and the public carrier provides the ADSL connection to the customer.

ADSL2 and ADSL2+: Enhancing Transmission Speeds

Originally providing transmission speeds of up to 8 Mbps downstream and
1.544 Mbps upstream, ADSL has been enhanced twice:
ADSL2 offers up to 12 Mbps downstream and 1.544 Mbps upstream.
ADSL2+ provides up to 25 Mbps downstream and 1.544 Mbps upstream.
The maximum available bandwidth for either downstream or upstream
depends on factors such as:
Distance between the customer's premises and the public carrier's CO—
The greater the distance, the slower the transmission rate.
Line quality—The more noise on the line, the slower the transmission rate.
As Table 7-1 shows, to qualify for ADSL or ADSL2, customers can be a
maximum of 5.49 to 5.67 km from the public carrier's CO. For ADSL2+,
customers can be only 1.52 km away from the CO. If a company or home is
too far away from the public carrier's CO, ADSL is not even an option.
Table 7-1. Distance Supported by ADSL, ADSL2, and ADSL2+
Type of ADSL
ADSL
ADSL2
ADSL2+
Distance from CO
3.66 km to 5.49 km (12,000 to 18,000 feet)
3.84 to 5.67 km (12,600 to 18,600 feet)
1.52 km (5,000 feet)
ADSL WAN Connections
ADSL Overview
7-5