[Ns-bugs] [Bug 400] Wifi Muti-Hop Network not forwaring packets (atleast ARP)

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=400


Tom Henderson <tomh at tomh.org> changed:

           What    |Removed                     |Added
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                 CC|                            |tomh at tomh.org




--- Comment #1 from Tom Henderson <tomh at tomh.org>  2008-11-05 01:20:47 EDT ---
(In reply to comment #0)
> Created an attachment (id=289)
 --> (http://www.nsnam.org/bugzilla/attachment.cgi?id=289) [details]
> Test script were ns3 fails
> 
> Hi,
> 
> I am using ns3.2.1.RC2 and I cant setup a multi-hop network as follows:
> 
> TOPOLOGY:
> 
>      WIRED CSMA             WIRELESS CHANNEL
>    ______________
>    O            O  ))          (( O ))           (( O
>    N3           N0                N1                N2  
> 
> Here N1 hears packets from N2 and N0 but N2 can not communicate directly with
> N0. However, when I run it, N2 sends his ARP but N1 does not forward it to N0
> and therefore it is not able to communicate. I am using Global Routing and
> running OLSR on the wireless network. 

Yes, this will not work.  Proxy ARP is not supported, there is one subnet for
the entire adhoc network, and N2 assumes that everyone on the subnet is
reachable via one hop (and therefore ARPs for it).

If you configure a real network like this, you would run into the same problem,
due to the assumption that link and subnet are synonymous, but they are not in
this case.

> 
> P.S. Is there anyway to have a GOD mode ARP in which everybody knows everybody
> else's MAC address? If not, can you guys add this feature? Its probably easy to
> do but will take me longer to do than you guys.

But, you do not want N0's MAC address here because N2 cannot reach N0 anyway.

One solution would be to put /32 addresses on each wireless interface, but I
haven't tested that.  That, if OLSR could handle it, would eliminate the ARPing
for N0.  It would require some low-level configuration (probably not through
the helpers).

I think the answer is to work on a routing solution to this-- I will try to
look at it more tomorrow.


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