Schedules Transfer Protocol in Linux

Scheduled Transfer Protocol (STP) is a new ANSI specified connection-oriented data transfer protocol. In STP small control messages are used to allocate buffers on the remote host before any data transfer. This reduces the workload of the receiver considerably and makes hardware acceleration relatively simple to implement. Applications for the protocol include network attached storage (SCSI running over STP). The low-latency aspects of STP also make it a very attractive protocol for for clustering.

In this paper, we describe the design principles behind the protocol as well as the Linux implementation of STP, which supports zero-copy transmits on NIC's supported by the Linux 2.4 zero-copy patch and receives using a modified Alteon Tigon-II firmware. Finally, we compare the performance of STP and TCP.