The Point-to-Point Protocol

Point-to-Point Protocol

In networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes...

 over ATM

Asynchronous Transfer Mode

Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...

(PPPoA) is a network protocol for encapsulating

Encapsulation (networking)

In computer networking, encapsulation is a method of designing modular communication protocols in which logically separate functions in the network are abstracted from their underlying structures by inclusion or information hiding within higher level objects....

 PPP frames in AAL5. It is used mainly with DOCSIS

DOCSIS

Data Over Cable Service Interface Specification is an international telecommunications standard that permits the addition of high-speed data transfer to an existing cable TV system...

 and DSL

Digital Subscriber Line

Digital subscriber line is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop. In telecommunications marketing, the term DSL is widely understood to mean Asymmetric Digital Subscriber Line ,...

 carriers.

It offers standard PPP features such as authentication

Authentication

Authentication is the act of confirming the truth of an attribute of a datum or entity...

, encryption

Encryption

In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...

, and compression

Data compression

In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....

. 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

Point-to-Point Protocol over Ethernet

The Point-to-Point Protocol over Ethernet is a network protocol for encapsulating Point-to-Point Protocol frames inside Ethernet frames. It is used mainly with DSL services where individual users connect to the DSL modem over Ethernet and in plain Metro Ethernet networks...

. It also avoids the issues that PPPoE suffers from, related to having a MTU lower than that of standard Ethernet

Ethernet

Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....

 transmission protocols. It also supports (as does PPPoE) the encapsulation types: VC-MUX

VC-MUX

Virtual circuit multiplexing or VC-MUX is one of the two mechanisms for identifying the protocol carried in ATM Adaptation Layer 5 frames specified by RFC 2684, Multiprotocol Encapsulation over ATM....

 and LLC

Logical Link Control

The logical link control data communication protocol layer is the upper sub-layer of the data link layer in the seven-layer OSI reference model...

 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.

Configuration

Configuration of a PPPoA requires PPP configuration and ATM configuration. These data are generally stored in a cable modem

Cable modem

A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a HFC and RFoG infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high...

 or DSL modem, and may or may not be visible to - or configurable by - a user.

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 & Virtual Circuit Identifier
  Virtual Circuit Identifier
  A Virtual Channel Identifier is a unique identifier which indicates a particular virtual circuit on a network. It is a 16-bit field in the header of an ATM cell...
  
   (VPI/VCI), such as 0/32 (analogous to a phone number)
• Modulation (Type): such as G.DMT
• Multiplexing (Method): such as VC-MUX
  VC-MUX
  Virtual circuit multiplexing or VC-MUX is one of the two mechanisms for identifying the protocol carried in ATM Adaptation Layer 5 frames specified by RFC 2684, Multiprotocol Encapsulation over ATM....
  
   or LLC
  Logical Link Control
  The logical link control data communication protocol layer is the upper sub-layer of the data link layer in the seven-layer OSI reference model...
  
  

ATM configuration can either be performed manually, i.e., it may not be automatically negotiated, or it may be hard-coded (or pre-set) into the firmware

Firmware

In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...

 of a DSL modem provided by the user's ISP.

External links

• A typical PPPoA architecture diagram (out of date and no longer maintained)