how to force kerberos to use tcp instead of udp

[Marcel]

right now i use kerberos for windows kfw-1.3.1. i want to authenticate on a windows 2003 server. since 
windows 2003 server only supports tcp, i wanted to ask if anybody can tell me how to force kerberos 
ONLY to use tcp instead of udp.
right now i can also authenticate on my windows 2003 machien, but the first attempt to authenticate 
always fails. 
kr5adm-guide: "When sending a message to the KDC, the library will try using TCP before UDP if the 
size of the message is above udp_preference_list. If the message is smaller than udp_preference_list, 
then UDP will be tried before TCP. Regardless of the size, both protocols will be tried if the first attempt 
fails."
but i only need tcp!?