A Survey of User-Level Network Interfaces for System Area Networks
Shubhendu S. Mukherjee, Mark D. Hill · 1997
System Area Networks (SANs), such as Myricom Myrinet and IBM Vulcan, provide latency, bandwidth, and reliability that are orders of magnitude better than traditional local area networks. SAN benefits are, however, proffered to applications only if light-weight protocols (not TCP/IP) and efficient network interfaces are used. SAN benefits are squandered, for example, if applications must invoke the operating system to send and receive messages. In contrast, User-level Network Interfaces (ULNIs) allow host applications to directly access the network interface without compromising protection by memory mapping internal interface registers into user space (e.g., the Myricom Myrinet network interface). Future trends in processor and SAN performance improvement indicate that ULNI accesses will become a critical bottleneck ---if not the most critical bottleneck---in systems built around SANs. Although processor accesses to ULNI registers are simply reading and writing ULNI memory, almost all U...