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Chapter 1
Introduction
The 9A426-02 ATM Module is a hardware-based switching module that supports
multiple interfaces simultaneously. The module’s interconnecting interfaces
include:
• Up to two front panel ATM interfaces via user-installed ATM Port Interface
Modules (APIMs)
• A fixed interface to the SmartSwitch 9000’s Internal Network Bus (INB)
• A user-configurable interface to the SmartSwitch 9000’s Flexible Network Bus
(FNB-1 or FNB-2)
Each data packet, regardless of the interface in which the packet enters the
module (ATM, FNB, or INB), is initially converted into a common format known
as a canonical frame. Each canonical frame’s header section contains source and
destination information. All canonical frames are forwarded to the module’s
group of SmartSwitch Application Specific Integrated Circuits (ASICs)
collectively known as the SmartSwitch Core.
The SmartSwitch Core can process data in two modes: as a traditional switch or as
a Secure Fast Switch (SFS). When operating as a traditional switch, the Fast Packet
Switch makes filtering/forwarding decisions based on Destination Address, with
standard IEEE 802.1d learning. When operating in SFS mode, all
filtering/forwarding decisions are based on a Destination Address-Source
Address pair, and the associated receive/transmit port.
Canonical frames that enter the 9A426-02 Module via the backplane interface
(FNB or INB) and are destined for the module’s front panel interface(s), are
converted by the module’s ATM Network Interface Block (ANIB) into 53 byte
ATM cells. The ANIB uses a separate set of ASICs to perform hardware-based
packet to cell conversions. This conversion process is an integral part of the
module’s ability to provide high-performance interconnections between legacy
LANs and ATM attached networks.
