[Opensim-dev] Does OpenSim need to leave so many packets marked as reliable?

[Frisby, Adam]

I remember you suggesting this before, +1.

Adam

From: opensim-dev-bounces at lists.berlios.de [mailto:opensim-dev-bounces at lists.berlios.de] On Behalf Of Stefan Andersson
Sent: Thursday, 2 October 2008 9:54 PM
To: opensim-dev at lists.berlios.de
Subject: Re: [Opensim-dev] Does OpenSim need to leave so many packets marked as reliable?

Guys,

for some time now, I've been meaning to propose a quite different approach, of which we've actually already done some tests with good result;

the basic idea is to connect reliable packets with two delegates; an ack delegate and a nack delegate - the implication probably obvious:

when the packet gets acked, the ack delegate is called, when it's nacked, the nack. The packet is sent as a parameter.

what this would let us do, is to use the sent packet to figure out what the right course of action is;

for an update, for example, we could look that object up and see if it's there's been another more resent update sent; if so, we can discard this. If not - we can _recreate_ a more recent packet and send that instead.

We have done something similar for terrain, a terrain packet watchdog, which keeps track of what patches has been acked, and resends those that haven't after a timeout. This removes the atom bombing.

Best regards,
Stefan Andersson
Tribal Media AB

Join the 3d web revolution : http://tribalnet.se/



________________________________

> Date: Thu, 2 Oct 2008 21:00:44 +0100
> From: jjustincc at googlemail.com
> To: opensim-dev at lists.berlios.de
> Subject: Re: [Opensim-dev] Does OpenSim need to leave so many packets marked as reliable?
>
> Yes, it's possible that the situation is more complicated than simply marking all packets as reliable. It's also
> difficult to look at percentages since it does depends heavily on what you do.
>
> Also, apologies for suggesting I would change trunk earlier. I won't be making any changes there without more
> consultation, at least certainly not any change which is non-default. I forgot how complicated an area this is.
>
>
> Melanie wrote:
> > Hi again,
> >
> > there may be some object updates that can be sent unreliable. For
> > instance, all that have to do with moving objects (e.g. velocity !=
> > 0). but the initial object update can't be lost. Any object update
> > lost of the login burst is a ghost prim.
> >
> > Melanie
> >
> >
> > Justin Clark-Casey wrote:
> >> Hmm, I then did the obvious thing and compared it (unscientifically) with a couple of sessions on the Linden Lab grid.
> >> There, reliable packets appear to compromise approximately 40% of the transfer.
> >>
> >>
> >> -------- Original Message --------
> >> Subject: Does OpenSim need to leave so many packets marked as reliable?
> >> Date: Thu, 02 Oct 2008 19:32:57 +0100
> >> From: Justin Clark-Casey <jjustincc at googlemail.com>
> >> To: opensim-dev at lists.berlios.de
> >>
> >> Hi there,
> >>
> >> A vast number of the packets that we send out from OpenSim (usually >95% according to the statistics printed to the
> >> Linden viewer log on shutdown) are marked as reliable. This requires that the viewer respond with an ack, and it just
> >> doesn't appear that this is done very well when a large number of reliables are sent. A lot of acks never come and we
> >> often appear to end up resending thousands (or in the worst case tens of thousands) of packets.
> >>
> >> In a private experiment I've set Header.Reliable = false for the LayerDataPacket and ObjectUpdatePacket (which appear to
> >> be the greatest sent by count, and which are currently reliable by default in libOMV). Naturally, this cuts down the
> >> vast number of resends (and possibly some of the packet_out_of_order messages that come out on the console log) without
> >> any apparant ill effects. However, my testing has been pretty limited so I'm minded to wait until Monday before making
> >> any trunk changes, since then I can get a better load test with multiple avatars (this doesn't stop anybody else testing
> >> of course :-)
> >>
> >> Any opinions on this? Is there a good reason for these packets to remain reliable (when resends are probably rare
> >> anyway)? libOMV appears to mark every packet as reliable by default... and then OpenSim removes this from a couple of
> >> them but not from others.
> >>
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> >
>
>
> --
> justincc
> Justin Clark-Casey
> http://justincc.wordpress.com
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