In
computer networking, the
Point-to-Point Protocol
In computer networking, Point-to-Point Protocol (PPP) is a data link layer (layer 2) communication protocol between two routers directly without any host or any other networking in between. It can provide loop detection, authentication, transmissio ...
over
ATM (PPPoA) is a
layer 2 data-link protocol typically used to connect domestic broadband modems to ISPs via phone lines. It is used mainly with
DOCSIS and
DSL carriers, by
encapsulating PPP frames in ATM
AAL5. Point-to-Point Protocol over Asynchronous Transfer Mode (PPPoA) is specified by The Internet Engineering Task Force (IETF) in RFC 2364.
It offers standard
PPP features such as
authentication
Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an Logical assertion, assertion, such as the Digital identity, identity of a computer system user. In contrast with iden ...
,
encryption
In Cryptography law, cryptography, encryption (more specifically, Code, encoding) is the process of transforming information in a way that, ideally, only authorized parties can decode. This process converts the original representation of the inf ...
, and
compression. It also supports the encapsulation types:
VC-MUX and
LLC - se
RFC 2364
If it is used as the connection encapsulation method on an ATM based network it can reduce overhead significantly compared with
PPPoEoA – by between 0 and ~3.125% for long packets, depending on the packet length and also on the choices of header options in PPPoEoA – see
PPPoEoA protocol overheads. This is because it uses headers that are short so imposes minimal overheads, 2 bytes for PPP and 8 bytes for PPPoA (with the RFC2364 VC-MUX option) = 10 bytes.
RFC 2684
/ref>
It also avoids the issues that PPPoE suffers from, related to sometimes needing to use an IP MTU of 1492 bytes or less, lower than the standard 1500 bytes.
The use of PPPoA over PPPoE is not geographically significant; rather, it varies by the provider's preference.
Configuration
Configuration of a PPPoA requires PPP configuration and ATM configuration. These data are generally stored in a cable modem or DSL modem, and may or may not be visible to—or configurable by—an end-user
In product development, an end user (sometimes end-user) is a person who ultimately uses or is intended to ultimately use a product. The end user stands in contrast to users who support or maintain the product, such as sysops, system administrato ...
.
PPP configuration generally includes: user credentials, user name and password, and is unique to each user.
ATM configuration includes:
* Virtual channel link (VCL) – virtual path identifier and virtual channel identifier (VPI/VCI), such as 0/32 (analogous to a phone number)
* Modulation (Type): such as G.dmt
* Multiplexing (Method): such as VC-MUX or LLC
ATM configuration can either be performed manually, or it may be hard-coded (or pre-set) into the firmware
In computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, h ...
of a DSL modem provided by the user's ISP; it cannot be automatically negotiated.
See also
*PPPoE
The Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol for Encapsulation (networking), encapsulating Point-to-Point Protocol (PPP) frames inside Ethernet frames. It appeared in 1999, in the context of the boom of DSL as the solu ...
* PPPoX
* L2TP
* ATM
* DSL
Notes
{{Reflist
External links
A typical PPPoA architecture diagram
(out of date and no longer maintained)
Telecommunication protocols
Tunneling protocols