性能和可靠性是大規模fat-tree網路的兩個主要問題。 我們提出具容錯的群播演算機制，其保證無死結以及在k個以上錯誤同時發生時的連接性應用於k-ray n-tree的fat-tree網路。我們合併了群播和容錯的方法。 在群播方面，我們提出三個方法去提高性能及避開死結。 路徑選擇演算法會利用交換機及目標的標籤來決定要送往的路徑。 切割封包成flit循環送出的方法及群播先行的方法來避面免死節的發生。 在容錯方法，one-hop向量儲存每個交換機下方連線的狀態並且計算出有故障的交換機。 end-routing向量紀錄一個封包遇到故障交換機的數量並在適當時機停止重新路由的機制。另外，我們建立了額外的廣播樹來解決原本重新路由演算法無法解決的狀況。在實驗方面我們使用SystemC發展k-ray n-tree的模擬器來評量性能和可靠性。最後與之前相關的論文做比較，我們提出的方法在傳輸量分別比單播、多重區域標識、硬體為群播路由演算法高出220%、85%、16%。在容錯方面，我們也有相當好的性能及可靠度在微量的面積負擔。

Performance and fault-tolerance are two dominant issues in large scale fat-trees. In this work, we present a local fault-tolerant multicast routing that guarantees connection and deadlock-free in k-ray n-tree up to k simultaneous faults. For multicast, the path selection utilizes labels of the fat-tree to decide outgoing ports. The multicast-first and the flit-by-flit round robin scheduling are adopted to solve multicast deadlocks. For fault-tolerance, the one-hop vectors stores and determines the link fault status of a switch. The end-routing vector records the number of switch faults in a routing path to avoid unnecessarily re-routing. In addition, we build a spare broadcast tree for fault-tolerance under the worst fault cases including switch faults at the bottom level of the fat-tree. To evaluate performance of the proposed schemes, we have developed a systemC simulator for k-ray n-tree. Compared to the unicast, the multiple local identifier routing scheme(MLID), and the hardware-based Multicast(HWm), the proposed method increases throughput by up to 220%, 85%, and 16% respectively in the adjacent traffic pattern. The average latency of the proposed algorithm is 21% more than the unicast, 62% less than that of MLID and 25% less than that of HWm under the random traffic. Techniques used to realize faulttolerance are often at the expense of considerable performance degradation. Our proposed scheme has a graceful degradation in performance and a moderate increase in area overhead as the number of link or switch faults in the system increases.

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