Re: a clue to multicast addressing weirdness

[Padmaparna Haldar <haldar@ISI.EDU>]

Hi Lloyd,
         Node expandaddr and set-address-format expanded are not
equivalent, as the note in ns-address.tcl says:

#####################################################################
# IMPORTANT NOTE: Always use "Node expandaddr" to expand addresses
# instead of "$ns set-address-format expanded". the set-addr-format 
# is called internally and doesnot check for mcast or hier flags and 
# thus can result in errors. Hence "$ns set-address-format expanded" 
# should
# *not* be used as a replacement API for "Node expandaddr", 
# especially for multicast simulations.
#####################################################################

The above two methods perhaps should be merged to avoid confusion.

BTW, I remember having written to you about this very issue several
months back..anyways, hope this helps,

--Padma. 




On Tue, 12 Jan 1999, Lloyd Wood wrote:

> Today (11 January 1999) I grabbed and built all the daily snapshots.
> 
> As I reported previously several times last year, I have an
> interesting problem[*] involving my simulation scripts, large
> addressing spaces and multicast, and I now believe that if I haven't
> tracked down the cause of the problem, I've at least found a
> repeatable symptom. 
> 
> This could make a very nice change - eliminating it will probably help
> me track down any other remaining problems...
> 
> To wit; setting expanded address space in my scripts with:
>   Node expandaddr
> currently works just fine and dandy with the ns snapshot, even for
> some stupidly large simulation topologies I'd probably be better off
> running under SessionSim rather than the normal Simulator. (circa 600
> multicast nodes.)
> 
> Replacing that single 'Node expandaddr' line in my scripts with the
> more fashionable, recent and apparently equivalent:
>   $ns set-address-format expanded
> causes a segmentation fault that even tcl-debug can't catch. All the
> time. [irrespective of setting old flags or doing the new -multicast
> lines below].
> 
> I can repeat this behaviour with nam-example.tcl:
> 
> > ns nam-example.tcl 
> Flag variable Simulator::EnableMcast_ discontinued.
>          Use multicast methods as:
>                  % set ns [new Simulator -multicast on]
>                  % $ns multicast
> running nam...
> 
> the current nam-example.tcl uses Node expandaddr. If I change that
> line of nam-example.tcl to read
>    $ns set-address-format expanded
> and modify the script as suggested, I get the legendary and completely
> inscrutable[*]
> _o19: no target for slot 128
> that I previously been reported a couple of times last year.
> 
> Go back to Node expandaddr and the slot target error is vanquished -
> Hurrah! ['$ns set-address-format hierarchical 1 12' fails similarly
> to expanded for the example code and for my scripts.]
> 
> Right, so 'Node expandaddr' and '$ns set-address-format'
> don't appear to be behaving in any equivalent fashion whatsoever; I
> don't understand why the new clasy form fails. And I'm convinced that
> it really isn't my fault.
> 
> Node expandaddr seems to work for me. I like it.
> 
> Anyone? The actual multicast traffic part of my script 
> ns/lloyd/traffic/simplemcast.tcl
> is below; I'm using CtrMcast.
> 
> thanks,
> 
> L.
> 
> [*] well, to me, anyway.
> oh yes: http://www-mash.cs.berkeley.edu/ns/mcast.html
> have any changes been accomplished since last June? TIA.
> 
> <L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>
> 
> 
> # Pick multicast type for all nodes e.g. 
> # set mproto DM
> # set mproto dynamicDM
> # set mproto CtrMcast
> 
> set mproto CtrMcast
> 
> set group [Node allocaddr]
> 
> # set all nodes to be multicast nodes
> set mrthandle [$ns mrtproto $mproto {} ]
> 
> # simple graphics test - set up a simple multicast group
> 
> $mrthandle switch-treetype $group
> $mrthandle compute-mroutes
> 
> set m5 [new Agent/LossMonitor]
> $ns attach-agent $g(5) $m5
> 
> set m12 [new Agent/LossMonitor]
> $ns attach-agent $g(5) $m12
> 
> set udp0 [new Agent/UDP]
> $ns attach-agent $g(1) $udp0
> $udp0 set dst_ $group
> 
> set cbr0 [new Application/Traffic/CBR]
> $cbr0 attach-agent $udp0
> $udp0 set fid_ 1
> $ns color 1 Red
> 
> # setting the central router doesn't work
> # $mrthandle set-c-rp { n(20) }
> # debug 1
> 
> $ns at 0.1 "$cbr0 start"
> $ns at 1.0 "$g(5) join-group $m5 $group"
> $mrthandle compute-mroutes
> $ns at 2.0 "$g(12) join-group $m12 $group"
> $mrthandle compute-mroutes
> $ns at 3.0 "$g(32) join-group $m12 $group"
> $mrthandle compute-mroutes
> $ns at 4.0 "$g(44) join-group $m12 $group"
> $mrthandle compute-mroutes
> $ns at 5.5 "$g(32) leave-group $m12 $group"
> $mrthandle compute-mroutes
> 
> $ns at 10.0 "finish"
> 
> 
> 

------------------------------------------------
Be true to your work, your word, and your friend.
--Thoreau

Padmaparna Haldar
ISI/USC.
310.822.1511 #352