Hey guys, I just got a quick question about Frame Relay.

     I've been reading the BCRAN book published by Sybex, and I'm finding 
the frame relay chapter a bit confusing. A few paragraphs from the Sybex 
book state the following:
     "Committed burst size and excess burst size are the two types of burst 
sizes. Each of these sizes is measured over a specific time interval called 
the committed rate measurement interval. Committed burst size is the maximum 
amount of data that the network can guarantee will be delivered during the 
committed time interval. The excess burst size is the amount of traffic 
which the user may exceed the committed burst size.
     For example, take a user who buys a Frame Relay circuit with the 
following characteristics: 1544Kbs access rate, 256K CIR, 4 second committed 
time interval.
     The user is guaranteed a CIR of 256Kbps over a four-second period. The 
user could transmit 256Kbps for four seconds, and the network would ensure 
delivery. The user could alternately send 1024Kbps for one second, 
representing the committed burst. However for the remaining three seconds, 
there would be no guarantee of delivery for the excess burst traffic."

     When the author says "The user could alternately send 1024Kbps for one 
second, representing the committed burst.", is he defining the committed 
burst as any speed above the CIR that does not exceed the total amount of 
information (256Kbps * 4 second interval = 1024K, total info) allowed to be 
sent during the time interval ? I always thought of the committed burst rate 
as a rate of information agreed upon with the Telco. For example, I thought 
you could get a CIR of 256Kbps and a burst up to 512Kbps, or a CIR of 
256Kbps with a burst up to 1.544 Mbps.
     Could anyone do me the favor of defining committed burst rate and 
excess burst rate, and while you're at it differentiate between the two? :)

Thanks,
Fred Danson
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