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A fundamental problem that confronts QoS-aware service selection and composition is the efficient and timely QoS information obtainment. Current research on this problem usually involves query-based or monitoring-based methods. However, in a dynamic and volatile service oriented Computing (SOC) environment, these solutions suffer some or all of the limitations, such as cost, timeliness guarantee and salability. This paper presents Pat, a P2P based publish/subscribe system to disseminate new revised QoS information. Pat aims at reliable and efficient QoS information dissemination in large-scale SOC environments. It exploits specialized rendezvous points (RP) and a replicas mechanism to reduce the risk of subscriptions loss and consequently improve reliability. A reverse RP ring is designed to quicken subscription delivery and QoS information publication. In addition, an optimization mechanism for composite services is built into Pat, which helps to reduce notification traffic. Simulation results show that Pat is reliable, efficient and scalable.