The intention of this memo is to define a classification system for the communication requirements of any large-scale multicast application (LSMA). It is very unlikely one protocol can achieve a compromise between the diverse requirements of all the parties involved in any LSMA. It is therefore necessary to understand the worst-case scenarios in order to minimize the range of protocols needed. Dynamic protocol adaptation is likely to be necessary which will require logic to map particular combinations of requirements to particular mechanisms. Standardizing the way that applications define their requirements is a necessary step towards this. Classification is a first step towards standardization.

With the transition of services like telephony to be carried over IP networks there is the potential for catastrophic numbers of calls to fail whenever sufficient demand is focused on unpredictable points in the core IP network. This is well known; service differentiation helps but does not alleviate the problem -call admission control is required but seems expensive for the few occasions it is needed. This paper describes a BT-developed experimental mechanism (based on work done by TUDarmstadt within the Market Managed Multiservice Internet collaborative project -http://www.m3i.org/) called guaranteed QoS synthesis (GQS) that performs call admission for core IP networks for constant bit rate streams (voice and video). The mechanism is primarily aimed at Internet services but it may be possible to extend it for VPN applications. The GQS mechanism is economic to deploy and operate, and scales without any increase in complexity. It achieves these properties by keeping no flow state in the network and basing call admission decisions on the measured congestion across the network. The paper describes the high-level GQS architecture as well as some of the deployment issues and potential savings in the operational support area. How GQS enables the separation of the interconnect QoS and retail business models is also explained.

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