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

[Justin Clark-Casey]

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.

-- 
justincc
Justin Clark-Casey
http://justincc.wordpress.com