Our objectives are

• Timely delivery of messages with end-to-end temporal requirements.
• Dependability of communication services even in the presence of network node/link failures;
• Exploitation of open systems and emerging standards to develop architecture-neutral communication services and export a rich, well-defined API for diverse applications;

The network components identified and to be laid out in the layered network architecture include:

1. A set of APIs for specifying flows with QoS requirements, a set of QoS translation rules for converting the traffic/QoS characteristics to the parameters in the underlying message model, and a QoS negotiation/re-negotiation policy that takes into account of flexibility, compatibility (with RTP/RTCP), criticality (of message streams), and price/performance tradeoff.
   
   
2. A QoS coordinator that collaborates with the underlying unicast/multicast routing protocols, resource reservation mechanism, and traffic control and message scheduling module to perform schedulability check and admission control.
   
   
3. A unicast/multicast routing protocol that selects a unicast route or a multicast tree with sufficient network resources to support adequate QoS.
   
   
4. A resource reservation protocol (RSVP) which reserve communication resources, and coordinate traffic control and message scheduling at run-time.
   
   
5. A run-time traffic control and message scheduler which provides rate enforcement for bursty traffic, schedules messages on a link so as to maintain each message stream at its desired QoS, and achieves fault tolerance by using spatial redundancy and a simple last chance algorithm.
   
   
6. A traffic regulator and QoS monitor which polices message streams according to their flow specification, and interfaces with RTP/RTCP to monitor/report the QoS provided by the network.

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Date last modified -- August 16, 1998
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