4.4 Thin Coaxial Physical Topology
While longer stub cables inserted between the BNC Tee and the Ethernet interface may seem to work, they actually create signal reflections which cause electrical noise and result in frame errors. Frames lost due to frame errors are typically detected and retransmitted by the application software. Therefore, the system may appear to work when stubs are used since a small level of frame loss is not usually noticed right away.
FIGURE 4.3 Thin coax stub cable is incorrect
However, a large enough frame error rate can cause a high number of retransmissions and make the network appear to slow down. The electrical noise and frame loss get worse as the traffic level increases, causing the response time of applications over the network to plummet just when the demand is highest. You can avoid these problems by making sure that there are no stub cables in your thin Ethernet system.
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