The advertisement originated at downstream station
S6. Comparing the fairRates, S4 determines that the fairRate of S6 is more restrictive
(i.e., smaller) than its own fairRate. S4 propagates the advertised fairRate of S6
(5 units) instead of advertising its own fairRate (10 units). By advertising the more
restricted fairRate of S6, it is ensured that the condition bi/wi ?‰¤ fairRate is met for both
sets of contributing stations (i.e., S1??“S4, and S5??“S6). The result is that stations S1??“S3
are not aware of the less restrictive congestion being experienced by S4, and will not
limit the traffic destined to S5; this will not create a problem because if the congestion
at S4 becomes more restrictive than the congestion at S6 the result will be similar to
the next example.
Figure 12.7 illustrates the case in which stations S4 and S6 are again congested
but the fairRate computed by S4 is more restrictive (i.e., smaller) than the fairRate
computed by S6. Station S4 computes a fairRate of 10 units and receives an advertised
fairRate of 20 units originating from S6 and propagated by S5. Comparing the
fairRates, S4 determines that its fairRate is smaller than that of S6.
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