Extending TCP the Major Protocol of Transport Layer

As We’ve known for a while that the Internet is classified as a result of the race to optimise existing applications or en- hance security. Sometimes 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" [1]. Is the same true for TCP? In this Research we develop a methodology for evaluating middlebox behavior relating to TCP extensions and present the results of measurements conducted from multiple Survival points. The shortest answer is that Yes we can still extend TCP, but extensions’ design is very constrained as it needs to take into account prevalent middlebox behaviors. For instance, absolute sequence numbers cannot be embedded in options, as middleboxes can rewrite ISN and preserve undefined options. Sequence numbering also must be consistent for a TCP connection, because many middleboxes only allow through contiguous ?ows. We used these findings to analyze three proposed extensions to TCP. We find that MPTCP is likely to work correctly in the Internet or fall-back to regular TCP. TcpCrypt seems ready to be deployed, however it is fragile if resegmentation does happen for instance with hardware of?oad. Finally, TCP extended options in its current form is not safe to deploy.