[MUD-Dev] Subjective test facilities

[Ben Greear]

Lydia Leong wrote:
> On Jul 12,  1:48pm, "Richard A. Bartle" wrote:

>> Would developers be interested in being able to observe the
>> effects of lag, latency, audio and video degradation under their
>> direct control in laboratory conditions? Or is knowing the ping
>> enough?

> There are three major components of effective transmission
> quality: Latency (your "ping"), packet loss, and jitter (the
> variability in your latency). So knowing the ping is definitely
> not enough.

> Games (and VoIP applications, among other things) experience
> varying levels of impact from these variables, based on the way
> that they buffer data, handle retransmits, etc. Tools that can
> simulate different WAN environments (like Shunra) are highly
> useful for doing specific tests on specific codebases, but it's
> difficult to generalize a set of results from laboratory testing.

> Nonetheless, still very interesting, I think, especially if the
> lab were willing to test specific games upon request.

We have a tool very similar to Shunra's products.  I'm willing to
give out free licenses to non-commercial developers if someone wants
to set up a simulated testing environment.  With two Linux PCs and a
$600 VLAN-aware ethernet switch, our software can emulate 96
distinct WANs, for instance.

With regard to ping (ICMP), it is often given low priority by
routers, so even if your ping time is 120ms your UDP RTP packets may
travel round trip in 100ms.

There has been a good deal of research into VOIP and RTP stacks, so
my suggestion to anyone dealing with real-time streaming media would
be to investigate existing RTP implementations and research.

Ben

--
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com
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