by Floyd and Jacobson
There are many ways of detecting congestion
in a network. The method used in this paper detects congestion at
the gateway itself. This paper presents a congestion avoidance
method in packet-switched networks by detecting incipient congestion
based on average queue size. The gateway which detects potential
congestion could notify connections either by dropping packets
arriving at the gateway or by setting a bit in packet headers
which corresponds to a probability value as a function of the
average queue size. This probability value is proportional to
the connection's share of bandwidth through the gateway. The other
main point the paper discussed is the avoidance of global
synchronization and of a bias against bursty traffic by the
used of randomization in choosing which arriving packets to mark.
The RED gateway uses a low-pass filter to calculate the average
queue size. Thus, the short-term increases in queue size that result
from bursty traffic or from trasient congestion do not result in a
significant increase in the average queue size. When the average
queue size is larger than the maximum threshold then every arriving
packet is marked. When the average queue size is between the minimum
and maximum threshold, each arriving packet is marked with
probability p(a)... This paper did not present a method for
determining the minimum and maximum threshold values, which could be
network dependent, and therefore, could significantly affect the
overall throughput of the system. The paper did, however, suggest this
issue as future topic for development.
Hoa Cao
4-27-99