Traffic Management for the Available Bit Rate (ABR) Service in ...

6.23 Summary of the ERICA and ERICA+ Schemes
This chapter has examined the ERICA and ERICA+ schemes, explicit rate in-
dication schemes for congestion avoidance in ATM networks, and explained several
extensions and enhancements of the scheme. The scheme entails that the switches
periodically monitor their load on each link and determine a load factor, the available
capacity, and the number of currently active virtual channels. This information is
used to calculate a fair and e cient allocation of the available bandwidth to all con-
tending sources. The algorithm exhibits a fast transient response, and achives high
utilization and short delays, in addition to adapting to high variation in the capacity
and demand.
Based on the discussion of requirements of switch algorithms in chapter 3 we have
examined how each of these requirements can be tested. Using these techniques, we
presented a comprehensive performance evaluation of the ERICA switch algorithm
and demonstrated the e ect of several features and options of the algorithm. We
have examined the e ciency and delay requirements, the fairness of the scheme, its
transient and steady state performance, its scalability, and its adaptation to variable
capacityandvarious source tra c models. Simulation results have illustrated that the
algorithm gives optimal allocations, and rapidly adapts to load and capacity changes.
The performance of the algorithm was examined for various con gurations, source
models and background tra c patterns.
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