The basic virtual memory-mapped communication (VMMC) model provides protected, direct communication between the sender's and receiver's virtual address spaces, but it does not support high-level connection-oriented communication APIs well. This paper presents VMMC-2, an extension to the basic VMMC. We describe the design, implementation, and evaluate the performance of three mechanisms in VMMC-2: (1) a user-managed TLB mechanism for address translation which enables user libraries to dynamically manage the amount of pinned space and requires only driver support from many operating systems; (2) a transfer redirection mechanism which avoids copying on the receiver's side; (3) a reliable communication protocol at the data link layer which avoids copying on the sender's side.

To validate our extensions we implemented stream sockets on top of the VMMC-2{} running on a Myrinet network of Pentium PCs. This zero-copy sockets implementation provides a maximum bandwidth of over 84~Mbytes/s and a one-way latency of 20 ~ µ s.