With high speed networks supporting data rates of a few hundreds Mbps and distributed applications demanding high performance, existing communication system and protocol architectures are under discussion. In this report, we describe an implementation of the TCP/IP stack with TCP [1] in user space and IP in kernel space. The goal by placing TCP in user space is to obtain a flexible transport protocol which can in future allows integrated communication subsystems based on Application Level Framing (ALF) and Integrated Layer Processing (ILP) [2]. ALF and ILP are expected to achieve more efficient data transfer, and more application control in the communication process.