3Com MSR 50 Series Configuration Manual page 78

78 C 1: ATM
HAPTER AND
n
DSL I C
NTERFACE ONFIGURATION
Two types of ADSL modules/cards are available: ADSL over POTS and ADSL over
ISDN (ADSL-I).
Typical network topology for ADSL routers
The following figure shows a typical network topology for routers with ADSL
interfaces, where:
DSLAM at the central office (CO) end works as the central office equipment.
■
The router works as the customer premises equipment (CPE).
■
Figure 2 Typical network for an ADSL router
Splitter
Line
DSLAM
Phone
Line activation and deactivation
Before transmitting services, the CPE must activate the line. This is done through
handshake training and information exchange between the CO equipment and
the CPE.
A typical activation process may last 30 seconds, beginning with line negotiation
until the line comes up. During this process, the two parties examine line distance
and conditions against the line configuration template (which defines the ADSL
criteria, channel mode, uplink and downlink speeds, and noise tolerance) and
attempts to reach an agreement. If the activation succeeds, a communication
connection is set up between the two parties. When negotiating connection
parameters during the line activation, the CO equipment plays a master role to
provide and decide values for most parameters, while the CPE a slave role to
accept them.
Contrary to activation, deactivation tears down the communication connection
between the two parties. The router tests the performance of the line regularly.
Once it finds out that the line performance is deteriorating, it automatically
deactivates, retrains, and reactivates the line.
As ADSL transmission speed depends on distance and line quality heavily, make
sure regular twisted pairs are used and the cables are well connected when
connecting ADSL interfaces.
This section covers only the physical configurations of the ADSL interface. For
more information about how to configure ATM (including PVCs), refer to
Configuration" on page
ADSL
ADSL
Phone
ADSL Router
Server
127.
Eth
Hub
Host A Host B
"ATM