Operation
3-2
The Ethernet Network Interface Block (ENIB) converts Ethernet data packets
received through front panel ports into a common canonical format that allows
the Fast Packet Switching 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.
The Fast Packet Switch (FPS) is a hardware based switch design that is the key
building block of the MMAC-Plus. All filtering/forwarding decisions are made in
hardware as opposed to software as in traditional bridges. This custom hardware
allows the FPS to process over 150K frames per second. The FPS is designed to
support up to 64 ports that are shared between the host processor, the INB
backplane, and LAN/WAN interfaces on the front panel of MMAC-Plus
modules. The FPS can operate in two modes; as a traditional bridge or as a
SecureFast Packet Switch (SFPS). When operating in bridge mode, it makes
filtering /forwarding decisions based on Destination Address (DA), with
standard IEEE 802.1d learning. When operating in SFPS mode, all
filtering/forwarding decisions are made based on a DA-SA pair and its receive
port. These DA-SA pairs with the associated receive port are programmed into
the switch using Cabletron’s Automated Connection Management System
(ACMS). 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 supports modules
operating in bridge mode and SFPS mode simultaneously providing security
when/where needed and ease of configuration where security is not required.
The i960 host provides the SNMP protocol stacks, to support industry standard
MIBs. Additionally, Cabletron enterprise extension MIBs are supported for each
media type. Advanced management services, such as the Distributed LAN
Monitor, telnet and network address to MAC address mapping, are also provided
by the i960 host.
The Host engine sends and receives packets via the CPU FPS Interface. This
allows the bridge to perform spanning tree protocol and other bridging functions.
The SMB Interfaces provide communication to the Host Engine for management
functions.