The Point-to-Point Protocol over ATM (PPPoA) is a network protocol for encapsulating PPP frames in AAL5. It is used mainly with DOCSIS and DSL carriers.
It offers standard PPP features such as authentication, encryption, and compression. If it is used as the connection encapsulation method on an ATM based network it can reduce overhead slightly (around 0.58%) in comparison to PPPoE. It also avoids the issues that PPPoE suffers from, related to having a MTU lower than that of standard Ethernet transmission protocols. It also supports (as does PPPoE) the encapsulation types: VC-MUX and LLC based.
Point-to-Point Protocol over Asynchronous Transfer Mode (PPPoA) is specified in RFC 2364.
The use of PPPoA over PPPoE is not geographically significant; rather, it varies by the provider's preference.
Read more about Point-to-Point Protocol Over ATM: Configuration