Supporting fully adaptive routing in InfiniBand networks

InfiniBand is a new standard for communication between processing nodes and I/O devices as well as for interprocessor communication. The InfiniBand Architecture (IBA) supports distributed routing. However, routing in IBA is deterministic because forwarding tables store a single output port per destination ID. This prevents packets from using alternative paths when the requested output port is busy. Despite the fact that alternative paths could be selected at the source node to reach the same destination node, this is not effective enough to improve network performance. However, using adaptive routing could help to circumvent the congested areas in the network, leading to an increment in performance. In this paper, we propose a simple strategy to implement forwarding tables for IBA switches that support adaptive routing while still maintaining compatibility with the IBA specs. Adaptive routing can be enabled or disabled individually for each packet at the source node. Also, the proposed strategy enables the use in IBA of fully adaptive routing algorithms without using additional network resources to improve network performance. Evaluation results show that extending IBA switch capabilities with fully adaptive routing noticeably increases network performance. In particular, network throughput increases up to an average factor of 3.9.