xDSL Session Termination

The router supports Broadband Remote Access Server (B-RAS) applications, as shown in Figure 2. In this application, the router handles the aggregated output from the digital subscriber line access multiplexers (DSLAMs). Directly connected to the subscriber premises, the DSLAMs handle the copper termination and aggregate the traffic into a higher-speed uplink. The output from the DSLAM is fed into the router through a DS3 or OC3 link.

Figure 2: B-RAS Application

The router then performs several functions:

• PPP session termination and authentication checking through PAP or CHAP
• Coordination with DHCP servers and local IP pools to assign IP addresses
• Connection to RADIUS servers or use of domain names to associate subscribers with user profile information
• Support for RADIUS accounting to gather detailed billing information
• Application of the user profile to the user traffic flow, which could include QoS, VPN, and routing profiles

The output of the router is typically a high-speed link, such as OC3/STM1 to feed a core backbone router. Virtual routers can also be used to keep the traffic logically separate and to direct packets to different destinations. As shown in Figure 2, the packets can be directed to a CLEC, ISP, corporate VPN, or the Internet.

A large number of xDSL protocols are supported, including:

• IP/PPP/ATM
• IP/PPP/Ethernet/ATM
• IP/bridged Ethernet/ATM

See JUNOSe Broadband Access Configuration Guide, for information about configuring B-RAS.

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