Chapter 3
Operation
The 9H423-28 module is a twenty-nine port device. Two front panel RJ21 connectors support twenty-four 10BASE-T ports, along with two RJ45 connectors, ST fiber connectors and a slot for an FEPIM that support four 100BASE-T ports. Each of these twenty-eight ports is a separate collision domain, while the 29th port connects to INB-B.
As shown in Figure 3-1, Ethernet Network Interface Blocks (ENIBs) and Fast Ethernet Network Interface Blocks (FENIBs) convert data packets received from any of the 10BASE-T/100BASE ports into a canonical frame format before forwarding to the SmartSwitch ASIC, while the Internal Network Bus Network Interface Block (INB NIB) converts data packets received from the INB into a canonical format before forwarding to the SmartSwitch ASIC.
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.
