ns3 with real application

[Rabia Saleh]

Hi Tom

I have created a MANET using a Docker container and ns3 nodes as a hybrid network as shown in the graph below, but when I increase the number of ns3 nodes to 50 the ping stops working (docker container ping ns3 nodes) any suggestion, please?

[Tom Henderson]

What have you tried to do to debug this? I recommend the following
strategy.

1) find the number of nodes for which it stops working. For instance,
if it works for 29 and stops for 30, then you have two configurations to
compare

2) using ns-3 logging or using tools in the real network like tcpdump,
try to find the point at which you do not see the packets anymore

> ns3 nodes) any suggestion,manet.png please?
>

[Tommaso Pecorella]

My best guess is that your computer isn't powerful enough to run that many docker images [fast enough].

The problem is that if the ns-3 VM does not get enough CPU cycles, the ns-3 scheduler won't be able to process the events fast enough to satisfy the real-time requirements, and everything will go... bad.

If this happens, you could increase the priority of the ns-3 VM w.r.t. the other containers. This document could be relevant, but I never did experiment with it: https://docs.docker.com/config/containers/resource_constraints/

Another possibility is that the client and servers (the "native VMs") are filling the ns-3 channel, causing congestion. In that case the system can (basically) stop responding for every machine. A solution to that is to decrease the traffic rate, and to add a tail drop (or a more advanced queue management) to the NetDevices handing the Tap interfaces. This won't help a lot, but at least you'll see *something* passing through.

[Tom Henderson]

Another common problem when starting a large MANET simulation is that
the routers cause congestion as they simultaneously all try to
synchronize their databases. Try starting them one by one (e.g. start
one routing process, wait 5 seconds, start the next one, etc.).

[Rabia Saleh]

Hi Tommason and Tom

I greatly appreciate your reply. In this scenario, I used just one docker container and 49 ns3 nodes, and I think my laptop is good enough to run this scenario as I do not use a VM I use real Ubuntu OS. In other words, just one node is attached to the tap-bridge and docker container. 

[Tommaso Pecorella]

I'd have to investigate it. If you want you can contact me privately on Zulip (to debug it I'll need the scripts and all the details to reproduce it on one of my servers).

[Rabia Saleh]

Daer Tommason

Many thanks for your reply; it is much appreciated.

Yes, please I would like to contact you privately on Zulip. 

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[Tommaso Pecorella]

The link is https://ns-3.zulipchat.com (it's the official ns-3 zulip channel)