In order to allow the T/TCP code to be compiled into the kernel, all of the source code added to the kernel are enclosed in #ifdef CONFIG_RFC1644 and #endif. Any of the debugging information such as state changes and checksum verifications are enclosed in #ifdef CONFIG_RFC1644_DEBUG and #endif. These options can be selected when configuring the kernel. Since T/TCP is still experimental, the options are only enabled when you specify to prompt for incomplete or experimental features.
When T/TCP is compiled in, there is an increase in size of 3220 bytes in the kernel image.