BANDWIDTH EFFICIENCY OF THE NETWORKING BROAD-BAND SERVICES ARCHITECTURE - A CASE-STUDY

IBM's networking broadband services (NBBS) is a unique network control point architecture capable of managing both asynchronous transfer mod e (ATM) networks as well as more generic fast packet networks with var iable size packets. The NBBS traffic management functions provide valu e-added enhanced variable bit rate (VER) services based on statistical traffic descriptors in addition to providing ATM Forum compliant VER services based on deterministic rule-based traffic descriptors. In thi s paper, we first summarize NBBS traffic management functions that are relevant to our study. These include traffic estimation, monitoring, policing and dynamic bandwidth adaptation procedures. The NBBS traffic estimation and adaptation module has a novel feature that continuousl y monitors the source traffic and dynamically adjusts the bandwidth re served in the network links for the network connection when it detects a significant change in the connection traffic characteristics. The m ain contribution of this paper is to integrate all these functions in a trace driven simulation experiment to study their aggregate effect i n a general network setting using actual traffic traces. Based on obse rved SNA, TCP, and compressed video traces we observed that NBSS dynam ic bandwidth adaptation function provides a three-fold savings in band width use compared to static peak bandwidth allocation in our case stu dy. Our study also provides useful insights into network dimensioning problem in order to achieve a desired level of network availability fo r different services. Finally, we provide a simple formula for estimat ing the amount of bandwidth savings achieved through dynamic bandwidth adaptation versus static peak bandwidth allocation in a general netwo rk setting by making a comparison on the individual traces in isolatio n.