Re: Can't multicast w/simplex links?

[Huang Hai <thumahh@chpcc.edu.cn>]

Hello Daniel,

While joining a multicast tree, a node must send message to the sender
via the backward simplex link. But you can circumvent the problem by
using "Rendezvous Point(RP) rooted shared tree", set a virtual sender
node and make it the root of the "RP tree", then link the real sender
and the virtual sender with a simplex link. The newest snapshot of ns
will support it. The following script maybe work (not tested).

     set mproto CtrMcast
     set v-sender [$ns node]          #virtual sender
     set r-sender [$ns node]          #real sender

     set mrthandle [$ns mrtproto $mproto {}]
     $mrthandle set_c_rp [$v-sender]  # set the root of multicast
                                      # tree to be the virtual sender
     $ns simplex-link $r-sender $v-sender 1.0Mb 10ms DropTail
                                      # link real sender and virtual
                                      # sender with simplex link
                                      # NOTE: ALL OTHER LINKS should be
                                      # duplex link.

If you use old version of ns or cannot make it work, please contact me.

DF> My ns version is 2.1b4a.

DF> I'm trying to "broadcast" a message from one node to several others,
DF> using simplex links.  I tried to take ~ns/tcl/ex/newmcast/mcast1.tcl and
DF> change the duplex-links to simplex-links.  For example, I changed
DF>         $ns duplex-link $n0 $n1 1.5Mb 10ms DropTail
DF> to
DF>         $ns simplex-link $n0 $n1 1.5Mb 10ms DropTail
DF> and similarly elsewhere. (I also commented-out the duplex-link-op
DF> lines.)

DF> Why do I find no traffic is sent after making these changes?


DF> Thanks,
DF> --dan


DF> ---------------------------------------------------------------------------
DF>  Daniel Friedman    danielf@isr.umd.edu    http://www.isr.umd.edu/~danielf




Best regards,
 Huang                            mailto:thumahh@chpcc.edu.cn