Efci - 3Com CoreBuilder 9000 User Manual

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HAPTER RAFFIC

EFCI

M
ANAGEMENT
Figure 26 Setting up Traffic Management Control Flow
A network element in an pre-congested state sets the Explicit Forward
Congestion Indication (EFCI) congestion notification mechanism in a cell
header. It is part of the standard ABR class of service.
In Figure 27, the output ALP (1) senses pre-congestion and begins to
mark headers of outgoing cells with the EFCI notation. When these
marked cells arrive at their destination edge device, the EFCI marking is
detected and RM (Resource Management) cells carrying the congestion
indication are returned to the source edge device. The source system then
implements a protocol that adaptively lowers the cell rate of the
connection, tending to clear the congestion there. This is generally the
first traffic management method to be activated.