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Unformatted text preview: kets due to the scenarios discussed here? CS 522, v 0.94, d.medhi, W’99 15 11. Inverse problem: Find service rate for a given average delay
We now pay attention to the simplest design problem when just a single network link is considered.
We know that the average delay for M/M/1 model is given by: 1
T = , :
Suppose, you are given , the offered trafﬁc in arrival rate (based on forecasted data) and the requirement that the average link delay should not be more than Tmax . To meet this delay, Tmax , we need 1 T
, max
which implies: T 1 + :
max Thus, we get a bound on the minimum service rate required to meet the requirement. Since service rate
corresponds to the link speed, this mean we can determine minimum link speed required if the average
packet size is known. Although this is a simple result, it ties offered trafﬁc and QoS requirement to the
service rate to be provided.
Example # 3:
Suppose that the average arrival rate is 500 pps, and we are given that the average packet size is 4Kbits.
If the system goal i...
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 Fall '08
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 Computer Networks

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