Chapter 4: Operation
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4. OPERATION
This chapter describes the functions and operation of the LBH08x/LBH18x Switch.
4.1
Dual-Speed Functionality, and Switching
The LBH08x/LBH18x Hardened Industrial Switches provide eight switched
ports, one of which may be 100Mbps fiber on the Model LBH18x. The architecture
supports a dual-speed switching environment, with a built-in full-duplex “future-proof”
fiber port. The Model LBH08x has RJ-45 copper on all the ports with auto-negotiation
capability.
The switched RJ-45 ports are full-duplex and auto-sensing for speed. (See
section 2.2). When the connected device is 10 Mbps, the LBH18x obeys all the rules
of 10 Mbps Ethernet configurations. The 10 Mbps users share a 10 Mbps traffic
domain, and can “communicate with” 100Mbps users as well as 100Mbps domain.
Similarly, the 100Mbps traffic obeys the rules of 100Mbps Ethernet, and can
communicate with 10 Mbps domain too.
The LBH08x/LBH18x units are plug-and-play devices. There is no software
configuring to be done at installation or for maintenance. The internal functions of
both are described below.
Switching, Filtering and Forwarding
Each time a packet arrives on one of the switched ports, the decision is
taken to either filter or to forward the packet. Packets whose source and destination
addresses on the same port segment will be filtered, constraining them to one port
and relieving the rest of the network from processing them. A packet whose
destination address is on another port segment will be forwarded to the appropriate
port, and will not be sent to the other ports where it is not needed. Packets needed
for maintaining the operation of the network (such as occasional multi-cast packets)
are forwarded to all ports.
The LBH08x/LBH18x Industrial Switches operate in the store-and-forward
switching mode, which eliminates bad packets and enables peak performance to be
achieved when there is heavy traffic on the network.
Switching, Address Learning
The LBH08x/LBH18x units have address table capacity of 4K node
addresses, and are suitable for use in large networks. They are self-learning, so that
as nodes are added or removed or moved from one segment to another, the switch
automatically keeps up with node locations.
An address-aging algorithm causes least-used addresses to fall out in favor
of new frequently-used addresses. To reset the address buffer, cycle power down-
and-up.
