[sldev] Client bandwidth and server lag

[Tigro Spottystripes]

I'm sorry, but how does that explain packetloss not returning when I
move the slider back up?

Teravus Ovares escreveu:
> This message is looking at it from a slightly different point of view,
> however these are some observations about what happens with the client
> and OpenSimulator.
>
> Firstly, the client will adjust the actual throttle settings based on
> packet statistics that it internally keeps.    This means that the
> slider is a 'guideline' and the client will do it's own adjustment of
> that as the network conditions change.   With debug on, one can see on
> the OpenSimulator console, the viewer requesting the throttle set
> lower and higher as network conditions change.
>
> When a user logs in to a Simulator for the first time and has the
> bandwidth slider at 1.5m, they're prone to having missing prim (prim
> not displayed but, physics wise, if your character hit one of these
> prim that your viewer didn't get an update, it would be there).
> Subsequent logins seem to work fine regardless, though it can take
> longer.  (There's less to download in a sim once you've already been
> there[textures are cached, uuids are cached, etc])
>
> When a user sets the throttle at 300-500, they enjoy the best experience.
>
> When a user sets the throttle to 1.5m and their connection is barely
> able to support a low connection of 250KB, they have the poorest
> experience.    Additionally, it adds processing overhead on the UDP
> stack, Memory, and processor of the Simulator machine serving them.
> This, depending on the quality of the connection and the things that
> the client requests can become enough of a strain to bring the quality
> of the simulation down for everyone in some situations.
>
> This has been resolved recently, however, in the past, a single user
> experiencing connectivity issues with an improperly set throttle
> re-requesting images over and over again could consume 500MB worth of
> packet data queued up in the throttle system.    Additionally, this
> could produce a situation where too many acks are appended to a
> packet. :)
>
> The moral of the story is, set your bandwidth slider as close to your
> functional connection speed to linden lab's network as you can.  If
> you set it too low, things will come in slow and queue up in the
> memory of the server (reducing the available memory for other things).
>   If you set it too high, your packets will get lost on a router
> somewhere between Linden Lab's servers and your computer.  This will
> trigger the UDP Resend functionality...  and consume memory and
> processing time on the server.
>
> Just because your Internet connection is really fast, doesn't
> necessarily mean that your connection from your computer to Linden
> Lab's servers is fast.   If you set the network slider higher then
> your actual speed there, your experience will degrade.   The client
> will attempt to compensate for it, but it will not always succeed.
>
> Regards
>
> Teravus
>
> On 6/23/09, Tigro Spottystripes <tigrospottystripes at gmail.com> wrote:
>   
>> Colin Kern escreveu:
>>     
>>> On Tue, Jun 23, 2009 at 1:08 PM, Joel Foner<joel.foner at gmail.com> wrote:
>>>
>>>       
>>>>> That said, an awful lot of people crank the bandwidth up to 1.5mbps
>>>>> because they figure they have a 1.5mbit connection or better. That's
>>>>> often a mistake. Most ISPs overstate the capacity their networks by a
>>>>> good margin, and it's very unlikely that even a 3 mbit DSL connection
>>>>> provides highly reliable 1.5mbit downstream.
>>>>>
>>>>>           
>>>> But for most on cable or fiber it's only a part of what's available :)  Is
>>>> there a reason it's capped at 1.5Mbps?
>>>> For what it's worth, an easy place to check your actual bandwidth is here
>>>> http://www.speedtest.net/.
>>>> Joel
>>>>
>>>>         
>>> I noticed in Snowglobe the cap is much higher (6 mbps, IIRC).
>>>
>>> I have heard some people saying that lowering your bandwidth helps
>>> with "rubber-banding", which I think makes more sense.  If your
>>> bandwidth is too high, it might overload your own internet connection,
>>> causing latency problems.
>>>
>>> Colin
>>>
>>>       
>> With me, somthing I've noticed, usually when I have any noticeable
>> packetloss, if I move the bandwidth throttle all the way down for a few
>> (or several) seconds, the packetloss goes away, once it is gone I can
>> move the throttle back up and packetloss doesn't seem to return (either
>> until another login, or at least for a long time), there a few rare
>> times where doing this doesn't have any effect on the PL though, I
>> imagine that it has a different cause in these cases (I haven't tried
>> Snowlobe yet)
>>
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>
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