Is It Still Possible to Extend TCP?
The people have known for a while that the Internet has ossified as a result of the race to optimize existing applications or enhance security. NATs, performance-enhancing-proxies, firewalls and traffic normalizers are only a few of the middle-boxes that are deployed in the network and look beyond the IP header to do their job. IP itself can't be extended because "IP options are not an option". Is the same true for TCP? In this paper they develop a measurement methodology for evaluating middle-box behavior relating to TCP extensions and present the results of measurements conducted from multiple vantage points.