ZyXEL Communications Parental Control Gateway HS100/HS100W - Manual (Page 317)

HomeSafe User’s Guide
Troubleshooting B-1
Appendix B
PPPoE
PPPoE in Action
An ADSL modem bridges a PPP session over Ethernet (PPP over Ethernet, RFC 2516) from your
PC to an ATM PVC (Permanent Virtual Circuit) that connects to an xDSL Access Concentrator
where the PPP session terminates (see the next figure). One PVC can support any number of PPP
sessions from your LAN. PPPoE provides access control and billing functionality in a manner
similar to dial-up services using PPP.
Benefits of PPPoE
PPPoE offers the following benefits:
1. It provides you with a familiar dial-up networking (DUN) user interface.
2. It lessens the burden on the carriers of provisioning virtual circuits all the way to the ISP on multiple
switches for thousands of users. For GSTN (PSTN & ISDN), the switching fabric is already in place.
3. It allows the ISP to use the existing dial-up model to authenticate and (optionally) to provide
differentiated services.
Traditional Dial-up Scenario
The following diagram depicts a typical hardware configuration where the PCs use traditional
dial-up networking.
Diagram B-1 Single-PC per Modem Hardware Configuration
How PPPoE Works
The PPPoE driver makes the Ethernet appear as a serial link to the PC and the PC runs PPP over
it, while the modem bridges the Ethernet frames to the Access Concentrator (AC). Between the
AC and an ISP, the AC is acting as a L2TP (Layer 2 Tunneling Protocol) LAC (L2TP Access
Concentrator) and tunnels the PPP frames to the ISP. The L2TP tunnel is capable of carrying
multiple PPP sessions.