BCL-3: A high performance basic communication protocol for commodity superserver DAWNING-3000 This paper introduces the design and implementation of BCL-3, a high performance low-level communication software running on a cluster of SMPs (CLUMPS) called DAWNING-3000. BCL-3 provides flexible and sufficient functionality to fulfill the communication requirements of fundamental system software developed for DAWNING-3000 while guaranteeing security, scalability, and reliability. Important features of BCL-3 are presented in the paper, including special support for SMP and heterogeneous network environment, semi-user-level communication, reliable and ordered data transfer and scalable flow control. The performance evaluation of BCL-3 over Myrinet is also given.