The PPPoE interface to the access concentrator can be a Fast Ethernet interface on any Services Router, a Gigabit Ethernet interface on J4350 and J6350 Services Routers, an ATM-over-ADSL or ATM-over-SHDSL interface on all J-series Services Routers except the J2300, or an ATM-over-SHDSL interface on a J2300 Services Router. The PPPoE configuration is the same for both interfaces. The only difference is the encapsulation for the underlying interface to the access concentrator:
The Services Router encapsulates each PPP frame in an Ethernet frame and transports the frames over an Ethernet loop. Figure 32 shows a typical PPPoE session between a Services Router and an access concentrator on the Ethernet loop.
Figure 32: 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 Services Router 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 33 shows a typical PPPoE over ATM session between a Services Router and an access concentrator on an ADSL loop.
Figure 33: PPPoE Session on an ADSL Loop
