An Implementation of Diffusion in the Linux Kernel

Packet headers and trailers exhibit considerable coding redundancy from both a theoretical and a practical standpoint. Diffusion exploits this redundancy to create an additional communication channel between hosts as a by-product of normal packet transfers. This channel is zero cost: the number and size of packets transferred do not change. Information is piggybacked on existing packets by overwriting unused fields in their headers and trailers. Dissemination of dynamic resource information is a natural use of such a channel. This paper describes the interface, implementation, and performance of Diffusion on the Linux operating system. In addition, it describes two tools, SpyTalk and LoadBanner, which have been built on top of this implementation. It is also a user manual for those who wish to try Diffusion.