On LID assignment in infiniBand networks

To realize a path in an InfiniBand network, an address, known as Local IDentifier (LID)in the InfiniBand specification, must be assigned to the destination and used in the forwarding tables of intermediate switches to direct the traffic following the path. Hence, path computation in InfiniBand networks has two tasks: (1)computing the paths, and (2 )assigning LIDs to destinations (and using the LIDs in the forwarding tables to realize the paths). We will refer to the task of computing paths as routing and the task of assigning LIDs as LID assignment Existing path computation methods for InfiniBand networks integrate these two tasks in one phase. In this paper, we propose to separate routing and LID assignment into two phases so as to achieve the best performance for both routing and LID assignment. Since the routing component has been extensively studied and is fairly well understood, this paper focuses on LID assignment whose major issue is to minimize the number of LIDs required to support a routing. We prove that the problem of realizing a routing with a minimum number of LIDs is NP-complete, develop a number of heuristics for this problem, and evaluate the performance of the heuristics through simulation. Our results demonstrate that by separating routing from LID assignment and using the schemes that are known to achieve good performance for routing and LID assignment separately, more effective path computation methods than existing ones can be developed.