This document describes LOWPAN_TCPHC, a scheme for compressing the header of Transmission Control Protocol (TCP) segments, in order to reduce the overhead on low-power and lossy networks. It also specifies the LOWPAN_TCPHC header fields for the transmission of TCP segments over IPv6 for Low-power Wireless Personal Area Networks (6LoWPAN). In many cases, the 20 bytes of the mandatory TCP header can be compressed into as little as 6 bytes.