For this article, we will return to our fictional large scale service provider called AD-net Provider. It has its own service provider network, that would be called AD-net Internet (ADINET). ADINET is providing Internet access services and contents. The amount of ADSL subscribers increases rapidly, resulting in the complication of the IP network and increase of the user traffic.

AD-net Provider is increasing network bandwidth and is considering use of IPv6 and Multi Protocol Label Switching (MPLS) in future, to increase the quality of the service for the customers. Regional Operation Center has ADINET Point of Present and the Broadband Remote Access Server (B-RAS). POP is used for the user traffic routing, terminating ARM PVCs and combining Digital Subscriber Line Access Multiplexers (DSLAMs) from each Central Office.

There are four main architectures for access core networks:

• The transparent ATM core network architecture
• The Layer Two Tunneling Protocol (L2TP) Access Aggregation (LAA) architecture
• The PPP Terminated Aggregation (PTA) architecture
• Virtual Path Tunneling (VPT) architecture

The PPP architecture was selected by the AD-net Provider since it has some benefits comparing to other architectures:

• It can work with the pre existing dial-up infrastructure
• It provides benefits for subscriber management
• AAA functions
• Etc.

Two different kind of technology are required for transportation purposes of the PPP protocol: PPPoE and PPPoA. Since in order to access the Internet using ADSL and POP users have to get connected to ADINET, AD-net provider adopts the PTA architecture with PPPoA and PPPoE.

ADSL Termination Unit – Remote (ATU-R) can either be stand-alone type or plug-in type. Stand-alone type is using cheaper Ethernet card with the 10BaseT interface. Plug-in type of ATU-R is is using Network Interface Card (NIC) with the Peripheral Component Interconnect (PCI) interface. It provides the IPoA (IP over ATM), PPPoA and bridged mode by device drivers. It also can provide PPPoE architecture, but that will require drivers to be installed on the ATU-R and specialised software installed on the customer PC.