Operation
3-2
All data packets destined for a front panel port, the INB, or the i960 are converted
into the canonical format before forwarding to the SmartSwitch ASIC. Network
Interface Blocks (NIBS) check for valid data packets entering the system. If an
errored data packet is found, the SmartSwitch ASIC flags the error and does not
forward the errored data packet to any outbound ports. Once in this common
format, the SmartSwitch ASIC decides from header information the port
destination of data packets. Data packets are then converted from the canonical
format to the proper format for the interface destination whether it is a front panel
port, or connection to the INB.
ENIB
The Ethernet Network Interface Block (ENIB) converts Ethernet data packets
received through front panel ports into a common canonical format that allows
the SmartSwitch ASIC Engine to determine the proper destination port. The ENIB
also converts data packets from the common canonical format back to Ethernet
data packets for transmission out front panel ports.
SmartSwitch ASIC
The SmartSwitch ASIC is a hardware based switch design that is the key building
block of the MMAC-Plus hub. The SmartSwitch ASIC makes all filtering/
forwarding decisions in custom hardware as opposed to software like in
traditional bridges. This custom hardware enables the SmartSwitch ASIC to
process over 750K frames per second. The SmartSwitch ASIC is designed to
support up to 64 ports shared between the host processor, the INB backplane, and
LAN/WAN interfaces on the front panel of MMAC-Plus modules. The
SmartSwitch ASIC can operate in two modes; as a traditional switch
or as a
SecureFast Switch (SFS).
Traditional Switch
When operating as a traditional switch, the SmartSwitch ASIC makes filtering/
forwarding decisions based on Destination Address (DA), with standard IEEE
802.1d learning.
SecureFast Switch (SFS)
When operating as an SFS switch, the SmartSwitch ASIC makes all
filtering/forwarding decisions based on a Destination Address-Source Address
(DA-SA) pair and its receive port. These DA-SA pairs with the associated receive
port are programmed into the switch using Cabletron’s SecureFast Virtual
Network Server (SecureFast VNS). This provides the network administrator with
the ultimate network security without the performance degradation found when
using routers or bridges with special filtering capabilities. The MMAC-Plus hub
can support individual modules operating in the traditional switch mode or SFS
mode providing security where needed.
