Chapter 1 Introduction - Cabletron Systems 9A426-01 User Manual

Introduction
The 9A426-01 ATM SmartSwitch Module is a hardware-based switching module
that supports multiple interfaces simultaneously. The module's interconnecting
interfaces include:
• A front panel ATM interface via a user-installed ATM Port Interface Module
(APIM)
• A fixed interface to the SmartSwitch 9000 Internal Network Bus (INB)
• A user-configurable interface to the SmartSwitch 9000 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:
• Traditional Switch - When operating as a traditional switch, the Fast Packet
Switch makes filtering/forwarding decisions based on Destination Address,
with standard IEEE 802.1d learning.
• Secure Fast Switch (SFS) - 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 9A426-01 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.
Chapter 1
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