[ns] How to get the link's delay?

[sbchen <sbchen@iipc.zju.edu.cn>]

Dear Sir,
    I have setup a duplex link by
	$ns duplex-link $n0 $n1 1.5Mb 10ms DropTail
    Now I try to get the delay value by
	set link [$ns link $n0 $n1]
	set d [$link set delay_]
	puts "delay = $d"
    But ns can't read "delay_". I think "$ns link $n0 $n1" returns the 
link_($n0:$n1) and the "delay_" has been binded. But why here it
can not be read?
    If it is a not advisable way, then please tell me how to get a setuped
link's delay value!
    Thank you for your attention.

Sbchen