page 1  (21 pages)
2to next section

A Framework for QoS Updates

in a Networking Environment

Burkhard Stiller ?

University of Cambridge, Computer Laboratory
New Museums Site, Pembroke Street
Cambridge, CB2 3QR, England, U.K.
Phone: +44 +1223 334476, FAX: +44 +1223 334678
E-Mail: [email protected]


The support of sufficient Quality-of-Service (QoS) for applications residing in a distributed environment and running on top of high performance networks is a demanding issue. Currently, the areas to provide this support adequately include communication protocols, operating systems support, and offered network services. A configurable approach of communication protocols offers the needed protocol flexibility to react accordingly on various different requirements.

Communication protocols and operating systems have to be parametrized using internal configuration parameters, such as window sizes, retry counters, or scheduling mechanisms, that rely closely on requested application-oriented or network-dependent QoS, such as bandwidth or delay. Moreover, these internal parameters have to be recalculated from time to time due to network changes (such as congestion or line break-down) or due to application-specific alterations (such as enhanced bandwidth requirements or increased reliability) to adjust a temporary or semi-permanent out-of-tune" service behavior.

Therefore, a rule-based evaluation and QoS updating framework for configuration parameters in a networking environment has been developed. The resulting rulework" can be used within highly dynamic environments in a communication subsystem that offers the possibility to specify for every QoS parameter both a bounding interval of values and an average value. As an example, the framework has been integrated in the Function-based Communication Subsystem (F-CSS). Especially, an enhanced application service interface is offered, allowing for the specification of various QoS-parameters that are used to configure a sufficient application-tailored communication protocol.

?The author is currently on leave from Universit?at Karlsruhe, Institut f?ur Telematik, D-76128 Karlsruhe, Germany, and is sponsored by the Commission of the European Communities as a Research Fellow under the Human Capital and Mobility Scheme (RG 19327).