The MoSaKa QoS System: Architecture and Evaluation
Dipl.-Inf. Philipp Drieß
Dr.-Ing. Florian Evers
Dipl.-Inf. Markus Brückner
- To enable QoS over packet-switched transmission systems, multiple schemes exist such
as IntServ and DiffServ. As both schemes strongly depend on underlying
per-hop transmission systems that have parameters that do not change over time.
Problems arise if one applies them to wireless mobile transmission schemes such
as satellite-based schemes.
To support robust audio and video conferencing, an end-to-end reservation-based approach
is inevitable. This led to the development of a the MoSaKa QoS System,
which combines a reservation-based QoS scheme with the ability to deal with changing
link conditions. The main idea was to enable applications to degrade gracefully if an
unstable link deteriorates.
Each router implements a cross-layer-based QoS agent, which tracks the network-layer-based
QoS and takes the current status of the lower layers into account. Certain flows can be
suspended without canceling them if the capacity of a link deteriorates.
To select which flow has to be suspended, an Optimizer was implemented which
examines the flows for their priority and respective QoS requirements.
To depict how this optimizer works and how the system performs, a testbed with an
emulated satellite link was set up. The results of various tests and a performance comparison
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