Multiple Services Differentiation In Resilient Packet Ring

Resilient Packet Ring (RPR) is a new packet based layer2 access technology. It concentrates advantages of Ethernet's simplicity and cost-effectiveness and SDH/SONET's reliability, and it is a trend and shining technology for Metropolitan Area Networks (MAN).RPR is located in the Media Access Control (MAC) of OSI's data link layer. An introduction to the moduler design of RPR MAC is given and interfaces between RPR MAC and its client and those between RPR MAC and physical layer are introduced. Data path model of RPR is illustrated in the following paper. Several components are discussed, including structure of the model, MAC frame receiver and transmitter, theory of RPR shaper and the simple method that services in RPR are classified only three types including ClassA, ClassB and classC for service differentiation. Based on the study of RPR data path, we find that RPR has some shortages such as the coarse granularity in service differentiation and deficiencies of supporting multiple services differentiation, which causes RPR is inconvenience to interoperate with other network that support QoS of multiple services. Aimed at this point, an improved service differentiation algorithm is created, named Dynamic Class Select-Proportional Delay Differentiation (DCS-PDD). This algorithm can effectively solve problems such as the coarse granularity in service differentiation, unfairness to higher numbered queues leaded by spatial scheduling and deficiency of multiple services support for traffic across rings. Explanation of DCS and PDD are introduced in the following paper.In order to effectively provide configuration, management and maintenance of multiple services differentiation, a suggestion that using MSR as a client to RPR is brought forward. MSR is located in the Logical Link Control (LLC) of OSI's data link layer, which gives the concept of tributary and uses configurations for the tributary service's provision. RPR based MSR is emphasized in the second part of this paper including interfaces between MSR and its client, station structure of MSR, policing and security of tributary. At last, comparisons between MSR-RPR and RPR is given and conclusions that the former is better than the latter not only at the multiple services differentiation but also at the network construction are brought forward.