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

CHAPTER 6
THE ERICA AND ERICA+ SCHEMES
The ERICA scheme is built upon the ideas of the OSU scheme (described in
chapter 5. The key limitations of the OSU scheme were the incompatibility with
current ATM Forum Tra c Management 4.0 standards [32], and the long time taken
to converge to steady state (transient response) from arbitrary initial conditions in
complex con gurations.
The ERICA and ERICA+ schemes overcome the limitations of the OSU scheme,
while keeping the attractive features. Further, they are optimistic algorithms which
allocate rates to optimize for both the transient performance, as well as the steady
state performance. Since real networks are in a transient state most of the time
(sources starting and stopping, ABR capacity varying constantly), we believe that
a scheme deployed in real-world switches need to perform well under both transient
and steady state conditions.
This chapter is organized as follows. Section 6.1 describes the basic ERICA al-
gorithm. Modi cations of this basic algorithm are then presented one by one. The
simulation results and performance evaluation are described in section 6.22, while the
pseudocode for the algorithm can be found in appendix C.
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