Re: hierarchical, multicast routing etc

[Polly Huang <huang@catarina.usc.edu>]

> I have a question about using CtrMcast on a topology that includes 
> simplex links, though.
> 
> CtrMcast assumes fully duplex links throughout, and doesn't appear
> able either to cope with either asymmetric simplex routing or fail
> elegantly. (Mind you, that's probably covered by the 'Currently, only
> DV routing can generate multipath routes' in section 15.2.) 
> 
> I've experimented with encouraging various asymmetric routings via
> link weighting, but that appears to have no effect on the CtrMcast
> routing. And since 

CtrMcast probes the unicast routing table for next hop towards sources or
RPs. Since the default(hierarchical as well? Padma?) unicast routing
calculates shortest path according to hop count, I'm not surprised that
you couldn't get asymmetric routes out of changing link weight. I'd expect
CtrMcast behaves differently if you specify the unicast routing to be cost
based(remember seeing this in the doc, but don't recall excatly where). 

> 
> $mrthandle set-c-rp { <rendezvous point nodes> } 
> 
> errors for me:
> 
> hierarchical routing:
> _o6414: unable to dispatch method set-c-rp
> 
> etc, meaning I can't set explicit rendezvous points, I appear to have
> no control over how CtrMcast spans the group - although it does span
> the group.
> 
> Cheers,
> 
> L.
> 

It seems to me that the following error is due to the change in 
link/node indexing for hierarchical routings. Am I right, Padma?

-Polly

> As for simplex errors with CtrMcast:
> 
> ns: _o3116 join-group _o5342 0x8000: can't read "link_(6:5)": no such
> element in array
>     while executing
> "return $link_($from:$to)"
>     (procedure "_o4" line 6)
>     (Simulator RPF-link line 6)
>     invoked from within
> "$ns RPF-link $target [$upstreamtmp id] $tmp"
>     (procedure "_o4827" line 33)
>     (CtrMcastComp compute-branch line 33)
>     invoked from within
> "$Agent compute-branch $s $group [$Node id]"
>     (procedure "_o4970" line 27)
>     (CtrMcast join-group line 27)
>     invoked from within
> "$proto join-group $group"
>     (procedure "_o3120" line 4)
>     (McastProtoArbiter join-group line 4)
>     invoked from within
> "$mcastproto_ join-group $group"
>     (procedure "_o3116" line 5)
>     (Node join-group line 5)
>     invoked from within
> "_o3116 join-group _o5342 0x8000"
> 
> 
> <http://www.ee.surrey.ac.uk/Personal/L.Wood/>PGP<L.Wood@surrey.ac.uk>
> 
> 
> 
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