Efficient TCP enhancements for Hybrid NetworksByRamesh SrinivasanThe original TCP design and implementation still has widespread deployment today among the devices in the Internet, including various end-devices/clients ranging from main-frames, large servers, desktops, laptops, palm-tops, notebooks, notepads, smart-phones, tablets and now various IoT (Internet of Things) devices. The TCP architecture and design, most of it put in place in the 1980s and shortly thereafter prior to the Internet boom, was intended solely for a wired network. One of the main in-built assumptions, due to the above design, is that any packet drops or delays are interpreted as solely due to a congestion in the network and corresponding adjustments/changes are made by the protocol. However, with the advent of wireless networks and their co-existence with existing wired Internet deployment, the legacy TCP implementation ends up inadvertently responding to packet losses and increased latencies, due to wireless-link errors, as if it were due to network-congestion. This results in significantly reduced throughput and efficiencies.WSC-TCP (Wireless Santa Cruz - TCP) proposed here, is an efficient TCP enhancement for today’s hybrid networks, which have both wireless as well as wired-links. It is a culmination of attempts to arrive at a framework to enable the TCP stack to differentiate those delays and losses, which are due to wireless-link-layer issues versus those that are due to actual network-congestion issues. The effort involved a study of the different mechanisms in the existing TCP design that do not work as per the original intent of responding only to network-congestion, due to its reliance on packet RTT (Round trip time) and related metrics for detecting and sizing the network congestion in today’s hybrid networks (wireless and wired links). The simulation tests conducted with some of the proposed enhancements result in an overall improved throughput/performance by 10-15% compared to TCP New-Reno in a hybrid network (wired and wireless links).