Summary: IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. IT-33, NO. 2, MARCH1987 219
Ultimate Instability of Exponential Back-Off
Protocol for Acknowledgment-Based
Transmission Control of Random
DAVID J. ALDOUS
Abstracr-When several users simultaneously transmit over a shared
communication channel, the messages are lost and must be retransmitted
later. Various protocols specifying when to retransmit have been proposed
and studied in recent years. One protocol is "binary exponential back-off,"
used in the local area network Efhernet. A mathematical model with
several idealizations (discrete time slots, infinite users, no deletions) is
shown to be unstable in that the asymptotic rate of successful transmis-
sions is zero, however small the arrival rate.
M ULTIACCESS communication channelshave been
the object of intense study in recent years, moti-
vated by problems of communicationsbetweencomputers.
A special journal issue  provides an overview of the
field; Kelly [7, sec. 41 gives a concise account of the