[Opensim-dev] Modifying the networking stack

[Diva Canto]

The viewers send a constant stream of agent update packets, whether the 
user is doing something or not. If a user is standing, not moving, not 
interacting with anything, the stream continues. I always found this to 
be really wasteful, and I'm not sure why the viewers do that.We ignore a 
considerable amount of these insignificant update packets, but even so, 
it is traffic that the server doesn't need.

Some details here:
http://tagide.com/blog/2014/04/optimizing-opensimulator-part-i/
And the preprint of the paper is here:
http://www.ics.uci.edu/~lopes/documents/summersim14/gabrielova_lopes_preprint.pdf

It would be nice to understand why the viewers behave the way they do 
and whether it would be possible to quiet them down.


On 11/13/2014 6:16 PM, Maxwell, Douglas CIV USARMY ARL (US) wrote:
> Currently we are profiling the simulator under various states of load and have observed what might be excess UDP traffic.  Has anyone else performed this kind of testing and would be willing to compare notes?
>
> Douglas Maxwell, MSME
> Science and Technology Manager
> Virtual World Strategic Applications
> U.S. Army Research Lab
> Simulation & Training Technology Center (STTC)
> (c) (407) 242-0209
>
> ________________________________________
> From: opensim-dev-bounces at opensimulator.org [opensim-dev-bounces at opensimulator.org] on behalf of Diva Canto [diva at metaverseink.com]
> Sent: Thursday, November 13, 2014 4:50 PM
> To: opensim-dev at opensimulator.org
> Subject: Re: [Opensim-dev] Modifying the networking stack
>
> What problem are you trying to solve? It's hard to comment without
> knowing what you want to achieve, but here are some random observations
> that you may want to take into account.
>
> As far as I remember, the reliable packets are a very small percentage
> of the UDP traffic at this point, so I'm not sure it's worth creating a
> dedicated TCP channel for them. Moving the HTTP traffic to the same TCP
> connection seems like a bad idea, as the HTTP traffic tends to be
> dominated by big data (textures, assets, etc) which would then get in
> the way of the small packets like AgentOnline, etc. I suspect it would
> make the client less responsive than what it is now.
>
> There is already support for WebSockets in OpenSim. It may not be
> complete, so I would encourage you to build on that. I am aware of WebGL
> clients that use WebSockets with OpenSim, and they have the same problem
> as described above: the big data gets in the way of the small packets,
> making the clients less responsive at points. But since WebGL is
> inevitable, your effort is probably best invested in this than in a TCP
> channel.
>
> Best,
> Diva
>
> On 11/13/2014 1:18 PM, Michael Heilmann wrote:
>> Greetings everyone
>>
>> I and another MOSES developer are going to be looking at the
>> client/server network stack, as well as the processing queue's used
>> for incoming and outgoing packets.  I am going to see if I can
>> implement a client stack on opensim and firestorm that uses the
>> traditional TCP/UDP pairing for this type of client<->server
>> relationship.  I have two thoughts, but I am interested in hearing if
>> you have ideas or insight into this particular space.
>>
>> Idea 1:
>>      Add a dedicated tcp port next to the UDP port, and move reliable
>> transport transmissions to the tcp port.  I am uncomfortable
>> increasing the required ports for each region, but the http server is
>> in the way.  I can look to move all communications from http to a tcp
>> socket-server type of deployment, at the expense of simple POST/GET
>> operations
>>
>> idea 2:
>>      Look into increasing the performance of the http server of the
>> regions, as well as testing/implementing a full websockets
>> implementation, and using the websockets upgrade for consistent client
>> connections.  This could eventually lead to javascript-based clients,
>> and does not remove http functionality.
>>
>> Either idea would see any traffic requiring reliable transport shifted
>> off of the current UDP stack, and onto the tcp reliable transport.
>> Either idea also will require modifications to a client to match.  I,
>> and another developer here, would be developing the client code, the
>> region code, and testing against a MOSES deployment.  As we are MOSES
>> developers, we would be working against simian instead of Robust; so
>> there would be a gap for regular Robust-based grids.
>>
>> If you could lend me your opinions about these ideas, the management
>> queues, associated problems in opensim, etc, I would really appreciate
>> it.  We would be working completely in the open on github, and obeying
>> all licensing.  We would welcome any and all cooperation, and we will
>> cooperate ourselves wherever we are welcome, but we are not interested
>> in avoiding positive changes to maintain SecondLife compatibility.
>>
>> Thanks.
>>
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