Hello,
I had to spend this nice warm saturday afternoon debugging ns-2
:
( since I encountered the
Classifier::no-slot error. A quick search on www.isi.edu/nsnam
revealed lots of such queries, but few solutions that I could
directly apply.
If you encounter the same error, this is probably the first (and
easiest?) solution that you should try.
In my TCL script I was connecting the UDP and SINK agents
before
attaching them to the nodes. For e.g., my script had
set udp_(0) [ new Agent/UDP]
set sink_(0) [ new Agent/LossMonitor ]
# set some parameters, including attaching the CBR
$ns connect $udp_(0) $sink_(0) ### here goes one saturday afternoon
$ns attach-agent $node_(1) $udp_(0)
$ns attach-agent $node_(0) $sink_(0)
I believe that it is this which causes the error - with my belief
being supported by the following facts:
a) my simulation works if I move the "$ns connect $udp(0) $sink(0)"
line to after the attach-agent's line with everything else remaining
the same.
b) the following comment in ns-lib.tcl : "#XXX need to check that
agents are attached to nodes already"
In summary, if you connect the agents before attaching them to the
nodes, then I have verified that:
a) in the connect call, the UDP agent immediately gets the ip of
the sink which is -1 since the sink is not (yet!) attached to any
node.
- see simplex-connect in ns-lib.tcl
b) The UDP agent sends packets out with a destination of -1 for
which the classifier is unable to find a slot, and hence (correctly)
complains.
- use gdb and tcldebug
Of course, YMMV and the standard disclaimers apply - especially
because I am sure that there are other ways to get the same error.
~Madhu.
