[ns] need help about CBK errors

[Nashid Shahriar]

Hi,
 I am using ns-2.31 mobile nodes and generating a trace file with
new-trace. In the trace file i found that some packets are getting
dropped and the reason is CBK. My queries are
>  What is correct meaning of CBK?
>  How to avoid CBK errors in a network?
>  Why such type of errors occur?
>  Do you know what is the meaning of seed in the cbrgen.tcl( traffic generation tool)

I will be highly graceful if i get solution of the query from you or
can u refer the source where can i get solution.

Thaking you,
dhrubo