--- On Sun, 6/2/11, raviteja bl <i_ravitej...@yahoo.co.in> wrote: From: raviteja bl <i_ravitej...@yahoo.co.in> Subject: Scheduler: attempt to schedule an event with a NULL handler. To: ns-users@ISI.EDU Date: Sunday, 6 February, 2011, 9:29 PM hello i am trying to make changes in red. after making changes when i run the tcl script im getting the following error Scheduler: attempt to schedule an event with a NULL handler. plz help regards raviteja