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Suppose now that smoehow the router knows it should give priority to packets from the 1 Mbps audio application.
Since the outgoing link speed is 1.5 Mbps, even though the FTP packets receive lower priority, they will still, on average,
receive 0.5 Mbps of transmission service. But what happens if the audio application starts sending packets at a rate of 1.5
Mbps or higher the FTP packets will strave, they will not receive any service on the R1-to-R2 link. Similar problems
would occur if multiple applications all with the same priority, were sharing a link's bandwidth; one noncompliant flow could
degrade and ruin teh performance of the other flow.
Principle 2: It is desirable to provide a degree of isolation among traffic flows, so that one flow is not
adversely affected by another misbehaving flow.
An alternative approach for providing isolation among flows is for the link-level packet-scheduling mechanism to explicitly
allocate a fixed amount of link bandwidth to each application flow. The audio flow could be allocated 1 Mbps at R1,
and the FTP flow could be allocated 0.5 Mbps.
With strict enforcement of the link-level allocation of bandwidth, a flow can use only the amount of bandwidth that has
been allocated; it cannot u;tilize bandwidth that is not currently being used by the other applications.
Principle 3: While providing isolation among flows, it is desirable to use resources as efficiently as possible.
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