[ns] create-connection Error

["Shekhar Kshirsagar" <skshirsa@nortelnetworks.com>]

Title: create-connection Error

Hi I'm getting following error, when I specify 'Null' for the <dsttype> in
the call to create-connection.

        warning: using backward compatibility mode
        backward compat bug: need to update classMap for Null

Here is my create-connection call:
         set cbr0 [$ns create-connection cbr $nList($i) Null $nList($j) 1]

Can anybody please provide me a fix to this problem.
Which type can I use, instead of Null?

Thanks,
Shekhar