Point to Point Protocol over Ethernet - PPPoE: An implementation of the Point to Point Protocol (PPP) using Ethernet for the transport medium. PPPoE provides login, data packet connection and routing. PPPoE is generally used on DSL connections.

The use of PPPoE may introduce difficulties to users attempting to connect a network rather than a single PC to the internet. The problem is that if PPPoE is used, the DSL company's server will add control bytes to TCP/IP packets. The control information is used instead of the IP number to route packets to/from the end user. These modified packets will not be usable by non-PPPoE aware devices/computers. Some sort of PPPoE aware front end will be required between the DSL line and the network.

In the case of PPPoE and a single PC, the DSL service provider will provide software that will handle the PPPoE protocol details. The software may not be available for all systems. It may require special TCP/IP settings. DSL buyers using something other than common Windows variants should make sure that their DSL provider can supply PPPoE software for their OS.

Not all DSL providers use PPPoE, and not all of those that do are a problem. If PPPoE is used, some sort of "PPPoE-TCP/IP converter" is required between the end user and the DSL line. Some DSL providers will terminate their connection in an Ethernet "router" that provides the required conversion. Others will terminate it in a DSL modem that passes through PPPoE and expects the user to handle PPPoE protocol details. In the later case, a single (Windows) PC using the DSL provider software will probably have no problem. A network may require a PPPoE front end on their proxy server. Although PPPoE is a standard, the handling of some conditions such as packets that exceed the maximum size when PPP control data is added, may be different in different systems.

In general, Cable companies do not currently use PPPoE. Instead they put everyone on the same network and check to make sure that users requesting IP address leases are known and authorized.

PPPoE packages are available for Linux, but installing and configuring them in an off the shelf proxy server may not be for the faint of heart.

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