Connection admission control for bursty real-time traffic in a network with multiple service classes

#1. Field of the Invention

#The present invention relates to the field of telecommunications and networking, and more particularly, a method and apparatus for controlling connection admission in a network with multiple service classes and quality of service requirements.

#2. Description of Related Art

#The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, wherein like reference numerals designate corresponding parts in the various drawings, and wherein:

#FIG. 1 illustrates a diagram of a network employing the method of the present invention;

#FIG. 2 illustrates the multiplexer model in an ATM switch;

#FIG. 1 illustrates a diagram of an ATM network 100 employing the method of the present invention including user terminals 101 connected to an ATM hub 102, and an ATM switch 103 connected to the ATM hub 102 and a public ATM network 104. The method of this invention will be described as implemented by an ATM network. ATM is useful as an illustrative application of this invention in part because the definitions of Cell Loss Ratio (CLR) and Cell Delay Variation (CDV) are understood concepts in the field. However, the method of this invention is not limited to this implementation. The method is also applicable to any statistically-multiplexed system of bursty traffic. This includes systems which merge data units at any granularity of fixed or variable length, as well as multi-service/multi-class systems with multiplexed packet flows subject to connection setup CAC and scheduled by a work conserving per class fair queue scheduler. For example, the method of the present invention could be implemented by general packet networks such as an IP network with quality of service (QoS) levels. The above examples are given by way of illustration only, and should not be interpreted to limit the applicability of this invention other types of networks.

#FIG. 2 shows a preferred embodiment use for the queuing and scheduling of rtVBR VCs in a rtVBR scheduler 201 at some output link 204 of an ATM switch 103. The capacity available to rtVBR is allocated to the different VC queues (2031, 2032, . . . , 203N) proportional to their weight φ using some form of weighted fair queuing scheduling. FIG. 2 shows N VC queues (2031, 2032, . . . , 203N) with weight φi for VC queue i, i ε{1, 2, . . . , N } and a total buffer 202 for the rtVBR class equal to B. These N VC queues receive corresponding classes of network traffic from input links which have been omitted from FIG. 2 for clarity.

#As far as allocating the total buffer 202 to the different VCs, in a preferred embodiment a complete sharing arrangement whereby an arriving cell from any VC (2031, 2032, . . . , 203N) is lost only when the total buffer occupancy of all VCs reaches capacity B in the total buffer 202 is used. The use of complete sharing instead of partitioning maximizes the statistical multiplexing gain. With this buffer management option, an implication is that the cell losses experienced by each VC are independent of the scheduling discipline (independent of φi's) as long as the scheduler is work conserving. While the method of this invention will be described as implemented with the complete sharing arrangement, the method is not limited to this implementation. Other buffer management options including complete partitioning and partial partitioning of the buffer could also be implemented.