[ns] Error with PING part 2

["E.Vijay" <evijay@ieee.org>]

Hi all,
sorry left out the relevant code:
......
Agent/Ping instproc recv {from stime rtt} {
    global sampling_interval f_rtt
    $self instvar node_
    set ns [Simulator instance]
    set now [$ns now]
    puts $f_rtt "$from $stime $rtt"
}

# Create ping agents and attach them to each route
for {set i 0} {$i <= $N} {incr i} {
    set send_ping($i) [new Agent/Ping]
    # make sure forward ping packets are the same sizes as normal packets
    $send_ping($i) set packetSize_ $packet_size
    $ns attach-agent $srcn($i) $send_ping($i)
    set recv_ping($i) [new Agent/Ping]
    # backward ping packets should be the same sizes as acks
    $ns attach-agent $dstn($i) $recv_ping($i)
    # Connect the two agents
    $ns connect $send_ping($i) $recv_ping($i)
    puts $f_rtt "% ping route $i = [$dstn($i) set id_]"
    # schedule the ping's
    set ping_time $str_start_t
    while {$ping_time < $T} {
 $ns at [expr $ping_time + $i*$sampling_interval/($N+1)] "$send_ping($i)
send"
 set ping_time [expr $ping_time + $sampling_interval]
    }
}

.....
....



Thanks all
Vijay