The FECN mechanism is initiated when a DTE device sends
Frame Relay frames into the network. If the network is congested, DCE devices (Frame
Relay switches) set the FECN bit value of the frames to 1. When these frames reach the
destination DTE device, the address ?¬?eld with the FECN bit set indicates that these
frames experienced congestion in the path from source to destination. The DTE device
can relay this information to a higher-layer protocol for processing. Depending on the
implementation, ?¬‚ow control might be initiated or the indication might be ignored.
?– Backward explicit congestion noti?¬?cation (BECN): A bit in the address ?¬?eld of the
Frame Relay frame header. DCE devices set the value of the BECN bit to 1 in frames
that travel in the opposite direction of frames that have their FECN bit set. Setting
BECN bits to 1 informs the receiving DTE device that a particular path through the
network is congested. The DTE device can then relay this information to a higher-layer
protocol for processing. Depending on the implementation, ?¬‚ow control might be
initiated or the indication might be ignored.
Example: Frame Relay Terminology??”DLCI
As shown in Figure 8-22, Router A has two virtual circuits that are con?¬?gured on one
physical interface.
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