13: Configuring an ADSL interface
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© Virtual Access 2018
GW6600 Series User manual
Issue: 1.7
Page 126 of 519
13
Configuring an ADSL interface
13.1
ADSL connections
ADSL access services typically use the Asynchronous Transfer Mode (ATM) protocol to
provide a low level communications path between the user's access equipment and the
service provider head end. The headend may be a Broadband Access Server (BAS) that
sits, logically, behind the ADSL central office Digital Subscriber Line Access Multiplexer
(DSLAM) and is connected using an ATM backbone. ATM is a high-speed switching
technology where data is grouped into cells.
Connection between the user equipment and the BAS is then achieved using the Point-
to-Point Protocol (PPP) running over the ATM connection path. PPP is a defined industry
standard used widely to allow two devices to communicate across a logical link. It is
extensively deployed by service providers as a means of connecting customers to
Internet Protocol (IP)-based services, such as the Internet.
The method of running PPP between the user equipment and the BAS may be either
directly over the ATM layer (PPPoA) or over an intermediate Ethernet layer (PPPoE).
13.2
ADSL connection options on your router
You can configure two main types of ADSL service on your router:
•
ADSL routed PPPoA connection
•
ADSL bridged connection
If you select the routed PPP service, you can run the PPP over ATM (PPPoA) or over
Ethernet (PPPOE). The following diagrams illustrate the topology of these connections.
Figure 64: A routed ADSL connection over PPPoA