| A New Approach for Providing Quality of Service (QoS) in a Dynamic Network Environment
April 2000
Duncan Thomson, The MITRE Corporation
Nancy Schult, The MITRE Corporation
Mohammad Mirhakkak, The MITRE Corporation
ABSTRACT
This paper looks at issues involved in attempting to provide Quality
of Service (QoS) support in a dynamic environment. We focus on a resource
reservation based approach, which we believe is attractive for military
applications, but becomes especially difficult in a dynamic network
environment. This is because available resources reserved for a particular
flow may contract after they have been "committed" to the
flow, causing the reservation to be dropped. Our approach is to expand
the semantics of the reservation, so that instead of being a single
value indicating the level of service needed by an application, it becomes
a range of service levels in which the application can operate, together
with the current reserved value within that range. This provides the
network flexibility so that reservations can be maintained as network
conditions change. Rather than forcing the network to make a binary
"admit/fail" decision for each flow, the network provides
feedback to applications on the current reservation level. Based on
this feedback, applications can adapt their behavior to what the network
can support. We have developed a prototype implementation of this concept,
running as an extension to the Reservation Setup Protocol (RSVP) protocol.
We are currently evaluating the implementation in a testbed network
where we can vary link bandwidth. The testbed also includes several
adaptive applications (audio, video, data transfer) running over the
User Datagram Protocol (UDP). The paper discusses our approach, testbed,
experiences to date, and current plans.
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