regarding the constants used in the protocols

With phrase “periodic route interval” ❓ – you mean the route table update time, beacon broadcast interval etc.,?. If it is the case, you may find lot of timers in c code of every routing protocol. If there is any TCL command interface provided to handle those timers then we can use them from TCL script 😀 . Otherwise if we change one such interval or any other “parameter”, then it will require re-compilation 🙄 of ns2.