[AG-TECH] Unicast issues with vic/rat

Ivan R. Judson judson at mcs.anl.gov
Mon Jan 26 21:03:51 CST 2004


I'll apply it while I'm working on other vic stuff anyhow. I've also been
using the ag-media cvs module which means the rat patches for iphlpr.lib are
applied to vic as well. Dunno if that matters, but we're down to using a
single lib common and tcl/tk for the two apps.

I'll apply this patch to vic while I'm in here

--Ivan 

> -----Original Message-----
> From: owner-ag-dev at mcs.anl.gov 
> [mailto:owner-ag-dev at mcs.anl.gov] On Behalf Of Robert Olson
> Sent: Monday, January 26, 2004 8:50 PM
> To: ag-dev at mcs.anl.gov
> Subject: Fwd: Re: [AG-TECH] Unicast issues with vic/rat
> 
> Aha, cool. We should get this applied to the AG vic; should 
> reduce the firewall problems that folks are having.
> 
> --bob
> 
> >Date: Mon, 26 Jan 2004 18:44:27 -0800
> >From: Andrew Swan <aswan at cs.berkeley.edu>
> >To: Don Morton <Don.Morton at umontana.edu>
> >Cc: "Sergeant A. G. Tech" <ag-tech at mcs.anl.gov>,
> >    Jennifer Parham <jparham at cs.clemson.edu>, jeh at cs.clemson.edu,
> >    westall at cs.clemson.edu, Dan Schmiedt <willys at clemson.edu>,
> >    ron_crummett at hotmail.com
> >Subject: Re: [AG-TECH] Unicast issues with vic/rat
> >Mail-Followup-To: Don Morton <Don.Morton at umontana.edu>,
> >         "Sergeant A. G. Tech" <ag-tech at mcs.anl.gov>,
> >         Jennifer Parham <jparham at cs.clemson.edu>, 
> jeh at cs.clemson.edu,
> >         westall at cs.clemson.edu, Dan Schmiedt <willys at clemson.edu>,
> >         ron_crummett at hotmail.com
> >User-Agent: Mutt/1.4.1i
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> >
> >Don Morton wrote:
> > > For some reason, there are folks who are trying to 
> unicast in, and 
> > > the end result seems to be that "we" can see them, but they can't 
> > > see us.  Note that there's no multicast involved here - 
> in one case, 
> > > the bridge is simply being used as a "rendezvous point"
> > > for two unicast streams, but the same problems occur - I 
> seem to be 
> > > able to see/hear the remote site, but they can't see/hear me.
> > >
> > > [...]
> > >
> > > My vague understanding of vic/rat, used with the QuickBridge, is 
> > > that the clients send UDP datagrams out to the bridge on ports in 
> > > the 50000 range, and they seem to receive UDP datagrams 
> on ports in 
> > > the 32000 range, and it "should" be that simple.
> >
> >i'm not sure about rat but vic in unicast mode sends and receives on 
> >the same port, which is specified on the command line.  (the 
> ports in 
> >your example were in the 50000 range).  the source port in 
> packets sent 
> >from vic will be an "ephemeral port" chosen by the operating system 
> >which is likely what you are referring to as in the 32000 range.
> >
> >the behavior you describe is consistent with a nat or a 
> firewall that 
> >builds dynamic rules that assumes vic will receive packets 
> on the same 
> >port that it sends them from.
> >
> >for example, if the remote person joins your quickbridge on 
> port 50186, 
> >they start sending packets from source port
> >32456 (or some other port chosen by their operating system, but not 
> >port 50186).  upon seeing these packets, the nat or firewall 
> installs a 
> >rule to forward packets from source port
> >50186 on the quickbridge addressed to destination port 32456 back to 
> >the remote participant.  however, quickbridge is sending packets to 
> >destination port 50186 so they never reach the remote site.
> >
> >probably the easiest way to verify that this is the problem is to 
> >rebuild vic with the attached patch and run the modified 
> version at the 
> >remote site.  or if you have openmash vic installed, you can 
> just add 
> >the flag "-rtptv" to the vic command line to get the same effect.
> >
> >-Andrew
> >
> 




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