Specified as a new ITU-T standard, Multiple Services Ring (MSR) proposes the mechanism of multi-service provision over Resilient Packet Ring (RPR). MSR over RPR is a packet based network which is flexible and efficient for burst data transport, but it is vital to MSR providing a good Quality of Service (QoS) for real-time services. ITU-T defined MSR Service Data Unit (SDU) lengths in X.87 for real-time services, such SDU lengths play an important role in QoS provision. Moreover, the impact of the MSR-SDU length on MSR's performance for real-time services has not been addressed.
The characteristics of MSR are first reviewed, and two core concepts in MSR, Tributary and Tributary Cross Connection Relationship (TCCR) are introduced. Accordingly, the MSR protocol model and generic frame format are presented, followed by briefly comparing the similarities and dissimilarities between MSR and ATM. A simulation model is set up for performance evaluation, in which ten nodes are connected to form a ring with STM-64 links and a distance of three kilometers between adjacent nodes. The frame loss ratio, delay, and jitter characteristics are investigated by increasing the load of TDM circuit emulation (TCE) services or changing the MSR-SDU length while keeping the loads of Ethernet B and C tributaries unchanged. Some conclusions are drawn from the simulations made.
Resilient Packet Ring (RPR) specified by IEEE 802.17 is a new standard for Metropolitan Area Networks (MANs). One of RPR's characteristics is that it can support three priorities traffic in a single datapath, i.e., class A, class B and class C, ranging from high priority to low priority, respectively. Different entities such as shaping, scheduling, fairness, topology and protection coordinate to guarantee the Quality of Service (QoS) for different services. Various pieces of the datapath in RPR are tied together through logical queues, thus we investigate the datapath from the view of logical queues in this paper. With a detailed analysis of the MAC shaping mechanism in RPR, we propose some improvement to achieve better transport performance for RPR's three priorities traffic. Simulation results show that our improvement is efficient.