THE FIRST SYMPOSIUM ON COMPUTER NETWORKS, 30-31 May 1996

TITLE: Complete Buffer Sharing with Pushout Thresholds in ATM Networks
under Bursty Arrivals

AUTHORS: Ozgur Aras and Tugrul Dayar

ABSTRACT: Broadband Integrated Services Digital Networks (B-ISDNs) are to 
support multiple types of traffic such as voice, video, and data. The
Asynchronous Transfer Mode (ATM) is the transport technique of choice for 
B-ISDNs by the standards committees. In this mode of operation, all
information is carried using fixed size packets (called `cell's) so as to
share the network among multiple classes of traffic. Since multiclass
traffic will be carried on B-ISDNs, different quality of service
requirements will be imposed by different applications. One type of 
congestion control for ATM networks deals with discarding cells at ATM 
buffers in order to guarantee a prespecified cell loss rate. One bit in 
each ATM cell header is reserved to assign the space priority of cells. 
This bit indicates whether the given cell is high priority or low priority. 
Priority cell discarding is a buffer management scheme in which higher 
priority cells are favored in receiving buffer space. An efficient 
technique for determining the cells to be discarded when congestion occurs 
is the complete buffer sharing scheme with pushout thresholds. In the 
system under consideration, there are two classes of traffic arriving to an 
ATM buffer of size K. Time is divided into fixed size slots of length equal 
to one cell transmission time. The arrival of each traffic class to the 
buffer is modeled as an independent Interrupted Bernoulli Process (IBP). 
The effects of using complete buffer sharing with pushout thresholds versus 
partial buffer sharing with nested thresholds are investigated under loads 
of varying burstiness through simulation.

KEY WORDS: Asynchronous transfer mode, buffer management, pushout thresholds