As previously stated, the T/TCP protocol introduces seven new states into the original TCP state diagram [3]. Figure 6.1
Figure 6.1: T/TCP State Diagram
shows these new states marked with a star.
[3] describes the simple correspondence between the new starred states and their equivalent original states. This correspondence is shown in table 6.2
Table 6.1: Definition of State Transitions
. The two flags SENDSYN and SENDFIN indicate whether to send a SYN or FIN with the packet currently being constructed.
Table 6.2: Starred State Definitions
The current implementation of TCP in the kernel has to be modified to handle the new state transitions. Two new flags TF_SENDSYN and TF_SENDFIN have to be added to the sock structure. These flags are switched on as shown in table 6.2 and are used when constructing the packet to decide whether to set the SYN or the FIN flag.
The existing functions that need to be modified to handle the new states can be seen in table 6.3. The modifications involve adding in the equivalent starred state into state checking, for example,
Table 6.3: Functions to be modified for additional states