Implications and control of middleboxes in the internet

Middleboxes in the Internet have been explored, sometimes quite controversially, in operations, standardization, and the research community for more than 10 years. The main concern in the past has been their contradicting nature to the Internet's end-to-end principle. In the past, many have expressed concerns that middleboxes contradict the Internet's end-to-end principle that is often understood to posit that "intelligence" is placed in end system and network elements just forward packets. Middleboxes introduce functions beyond forwarding in the data path between a source and destination, as described, for example, in RFC 3234. RFC 3234 describes a wide range of middleboxes, from TCP performance enhancing proxies to transcoders.