Users have been complaining that their Frame Relay connection to the corporate site is very slow.
The network administrator suspects that the link is overloaded. Based on the partial output of the
Router # show frame relay pvc command shown in the graphic, which output value indicates to the
local router that traffic sent to the corporate site is experiencing congestion?
A.
DLCI=100
B.
last time PVC status changed 00:25:40
C.
in BECN packets 192
D.
in FECN packets 147
E.
in DF packets 0
Explanation:
First we should grasp the concept of BECN & FECN through an example:
Suppose Router A wants to send data to Router B through a Frame Relay network. If the network is
congested, Switch 1 (a DCE device) will set the FECN bit value of that frame to 1, indicating that
frame experienced congestion in the path from source to destination. This frame is forwarded to
Switch 2 and to Router B (with the FECN bit = 1). Switch 1 knows that the network is congesting so it
also sends frames back to Router A with BECN bit set to 1 to inform that path through the network is
congested.
In general, BECN is used on frames traveling away from the congested area to warn source devices
that congestion has occurred on that path while FECN is used to alert receiving devices if the frame
experiences congestion.
BECN also informs the transmitting devices to slow down the traffic a bit until the network returns to
normal state. The question asks “which output value indicates to the local router that traffic sent to
the corporate site is experiencing congestion” which means it asks about the returned parameter
which indicates congestion ->BECN.
