The device's PPPoE interface to the access concentrator can be a Fast Ethernet interface, a Gigabit Ethernet interface, an ATM-over-ADSL interface, or an ATM-over-SHDSL interface. The PPPoE configuration is the same for both interfaces. The only difference is the encapsulation for the underlying interface to the access concentrator:
The device encapsulates each PPP frame in an Ethernet frame and transports the frames over an Ethernet loop. Figure 24 shows a typical PPPoE session between a device and an access concentrator on the Ethernet loop.
Figure 24: PPPoE Session on the Ethernet Loop
When an ATM network is configured with a point-to-point connection, PPPoE can use ATM Adaptation Layer 5 (AAL5) for framing PPPoE-encapsulated packets. The AAL5 protocol provides a virtual connection between the client and the server within the same network. The device encapsulates each PPPoE frame in an ATM frame and transports each frame over an ADSL or SHDSL loop and a digital subscriber line access multiplexer (DSLAM). For example, Figure 25 shows a typical PPPoE over ATM session between a device and an access concentrator on an ADSL loop.
Figure 25: PPPoE Session on an ADSL Loop
 | Copyright © 2008, Juniper Networks, Inc. All rights reserved. Trademark Notice. | |