[Ns-bugs] [Bug 406] GlobalRouteManager behaviour after Ipv4 interface SetDown and SetUp procedure

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=406





--- Comment #22 from Egemen <egemen.cetinkaya at gmail.com>  2008-11-20 20:27:59 EDT ---
(In reply to comment #21)
> Created an attachment (id=310)
 --> (http://www.nsnam.org/bugzilla/attachment.cgi?id=310) [details]
> test program
> 
> This test program does some manipulation of the topology and uses the dynamic
> features of global routing to change the global routing tables.
> 
> //  Order of events
> //  At pre-simulation time, configure global routes.  Shortest path from
> //  n1 to n6 is via the direct point-to-point link
> //  At time 1s, start CBR traffic flow from n1 to n6
> //  At time 2s, set the n1 point-to-point interface to down
> //  At time 3s, call RecomputeGlobalRoutes() and traffic will
> //    start flowing again on the alternate path
> //  At time 4s, re-enable the n1/n6 interface to up.  Will not change routing
> //  At time 5s, call RecomputeGlobalRoutes() and traffic will start flowing 
> //    again on the original path
> 

First of all, let me thank you for your prompt and helpful support. I installed
the patch and the above test scenario works as you mention.

However, we found three potential problems as shown with the following
scenarios:

Scenario 1:

Problem Summary:
An alternate path is used only if the sink is attached to the ipv4 interface on
the alternate path. 

Testing:
In the above mentioned example, connect the sink application to i1i6 instead of
attaching to i5i6. Replace i5i6.GetAddress (1) with i1i6.GetAddress (1) in
line-133. No traffic flows between 3sec and 4 secs despite of an available
alternate link.

Scenario 2:

Problem Summary:
If the interface to which the sink is attached goes down, all traffic stops
even if there exists an alternate route to the destination node.

Order of events: (changes marked with '-->')
//  At pre-simulation time, configure global routes.  Shortest path from
//  n1 to n6 is via the direct point-to-point link
//  At time 1s, start CBR traffic flow from n1 to n6
//--->  At time 2s, set down the point-to-point interface *1* on node *n6*. T
//  The Traffic flow stops
//--->  At time 3s, call RecomputeGlobalRoutes() and traffic does *NOT*
//    flow again the alternate path
//  At time 4s, re-enable the n1/n6 interface to up.  Will not change routing
//---> The traffic will start flowing on the original path whether or not you
Recomute GlobalRoutes
//  At time 5s, call RecomputeGlobalRoutes() and traffic will continue to flow 


Scenario 3:

Problem Summary:
A link does not go down unless both the interfaces on either side of the link
are setdown, with the exception of source interface.

Testing:
In the example that you gave, setdown ipv4 interface on node 6 corresponding to
link 1-6. If no further steps are taken, the traffic continues to flow on the
this failed link (link 1-6). 

Please let me know if you want me to post the files for each of the above
scenarios.


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