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G-2 User’s Reference Guide
Committed Information Rate (CIR)
The Committed Information Rate is a tool your Frame Relay service provider uses to manage your PVCs. The
CIR measures the average amount of normal priority data your Frame Relay network will attempt to deliver in a
given time interval.
Committed Burst Size (B
c
)
The Committed Burst specifies the maximum amount of data that your Frame Relay service provider agrees to
transfer under normal conditions over the time interval T
c
. The value for T
c
is calculated with the formula:
T
c
= B
c
/CIR
Data in excess of B
c
may be discarded if the network becomes congested.
Excess Burst Size (B
e
)
The Excess Burst specifies the maximum amount of data that your Frame Relay service provider will attempt to
deliver over the time interval T
c
.
In the absence of congestion, data will be transmitted at a rate equal to or less than the excess burst. That rate
is calculated according to the following formula:
(1+ B
e
/ B
c
) * CIR = excess rate
Your Frame Relay service provider will attempt to deliver data containing excess bursts, but reserves the right
to discard excess bursts in order to manage congestion within the network.
Actions of a Frame Relay Network
where:
Access rate
M
a
x
. b
u
rs
t
r
a
t
e
CIR
data may be
discarded
send data
as received
discard all data
> B + B
ec
B + B
ec
c
B
o
T T + T
oc