Chapter 2
10
2.2 System Description
The ADSL devices provide asymmetric data transport from the Customer’s
network to a DSLAM at the Central Office. It can be deployed over existing
copper loops already supporting a plain old telephone service (POTS).
The ADSL devices configuration consists of the device at the Customer
premises interfacing with an ADSL standard compliant line card in a Digital
Subscriber Line Access Multiplexer (DSLAM) at the Central Office. Its very
rich feature set includes an easy-to-use Setup Wizard and DHCP support for
Plug-and-Play installation. It also provides an extensive Firewall for network
protection, and VPN capabilities for reduced cost of remote access
communications.
The AT-AR240E and the AT-AR250E can be configured and managed locally
or remotely via a PC connected to the remote unit, or using the Command Line
Interface (CLI) through a Telnet session, or through a Windows-based
configuration tool.
The ADSL devices support Permanent Virtual Circuits (PVC). Each PVC is
represented by a numeric pair denoted as a Virtual Path Identifier (VPI) and
Virtual Circuit Identifier (VCI). A VPI is a number used to switch a logical
group of Virtual Circuits as a unit. A VCI is a number assigned to a single
circuit to distinguish its cell traffic from other circuits. Each 12-bit VPI has the
address range 0-4095 and each 16-bit VCI has the address range 0-65535.
The ADSL devices supports all PCs using standard Ethernet 10BaseT or
100BaseT and TCP/IP protocols.
2.3 Routing
The ADSL devices include full-featured integrated IP routers. To route a
packet, two basic functions are used:
1 A path determination function- enables the device to select the
most
appropriate
interface
to
transmit a packet.
