Cabletron Systems SPECTRUM 1800 User Manual page 98

Frame Relay Status and Configuration
above the deÞned CIR can be marked as discard eligible (DE); frames with the DE
bit set are considered to be excess data, and will be discarded if the network
becomes congested.
If congestion occurs on the selected DLCI while throughput is greater than the CIR, and
the Outgoing Rate Control parameter (settable via the Frame Relay Port ConÞguration
TIP
window, described beginning on
drop to the CIR level.
B
C
Use this Þeld to enter the Committed Burst Size (B
DLCI by your frame relay provider. The committed burst size deÞnes the
maximum amount of data (in bits) that the network agrees to transfer, under
normal conditions, during a time interval T
intervalÓ) is calculated by dividing the committed burst size (B
committed information rate (CIR); it deÞnes the time interval during which the
user can send only B
below). Any trafÞc which exceeds this burst rate will be marked discard eligible
(DE), and discarded if the network becomes too congested. While sustained B
trafÞc rates are not guaranteed, B
B
E
You can view the amount of trafÞc on the selected physical interface which is marked as
discard eligible via the Frame Relay Congestion Stats window, described beginning on
TIP
page
B
E
Use this Þeld to enter the Excess Burst Size (B
your frame relay provider. The excess burst size deÞnes the amount of data (in
bits) over the committed burst size (B
during the time interval T
committed burst size (B
exceeding this value will be buffered in the FRX device. Note that DE frames are
considered to be B
BECN
The BECN Recovery Count provides a means for controlling the rate of return to
maximum trafÞc ßow after it has been reduced due to congestion. If a packet is
received on the selected DLCI with the BECN (backward explicit congestion
notiÞcation) bit set, the conÞgured B
value will become zero (limiting trafÞc ßow to the value conÞgured for B
This limit will remain in place until the DLCI receives a speciÞed number of
sequential packets without the BECN bit set: the number speciÞed by the BECN
Recovery Count. Each time the conÞgured number of sequential packets is
received, the effective B
value.
5-10
(In/Out)
amount of data and B
C
(described below).
5-22.
(In/Out)
) by the committed information rate (CIR)). Any data
C
excess data.
E
E
page 5-2) is set to Yes, the throughput will immediately
. T
C C
excess data (see deÞnition of B
E
trafÞc has a higher delivery probability than
C
) assigned to the selected DLCI by
E
) that the network will attempt to transfer
C
(remember, T is calculated by dividing the
C C
Out value will be ignored and the effective
E
Out will be increased by one-eighth of the conÞgured
) assigned to the selected
C
(also called the Òbandwidth
) by the
C
Configuring Frame Relay Ports
,
E
C
Out).
C