Extending TCP the Major Protocol of Transport Layer
Ashis Saklani, Vishal Gupta · Scientific Review · 2015
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 flows.  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 offload.  Finally,  TCP  extended  options  in  its  current  form  is  not  safe  to  deploy.