A Reliable Transport Protocol for Resource Constrained Nodes: CRCTP- Protocol Design

During the scope of two DRDC projects related to wireless sensor networksSASNet, Self-Healing Autonomous Network, 2007-2011 and WRSN, Wireless Radiation Sensor Network, 2012-2014, CRC designed a transport protocol called CRCTP CRC Transport Protocol. A Transport Protocol for Resource Constrained Nodes CRCTP - Protocol Design. The two de-facto transport protocols typically found in IP networks are TCP Transmission Control Protocol and UDP User Datagram Protocol. UDP does not provide guarantee of delivery, but it is useful when low latency is required. TCP does provide guaranteed delivery. The mechanism that TCP uses to provide its guaranty of delivery operates end-to-end, i.e. only the two communicating endpoints are involved. This means that a failed transmission, even though it fails at the last hop before the destination, is restarted completely. Also, TCP uses a congestion control mechanism that causes unnecessary delays in wireless networks, and particularly in multi-hop networks. These two reasons make TCP inefficient under some circumstances, and the latency introduced is unacceptable for some applications. CRCTP was designed with the objective of having a transport protocol that provides guaranteed delivery with the lowest latency and overhead possible. It is designed to operate on resource constrained nodes and networks with restricted bandwidth. Various techniques are used to lower the overhead, latency and memory consumption, such as hop-by-hop delivery guarantee mechanism, hybrid ACK and NACK confirmation, no congestion control at all, etc. This document presents the design of CRCTP. The design is generic such that the protocol can be implemented in most typical communications stack.