UDP vs. TCP distribution [was: Re: [e2e] Can feedback be generated...]

[Tristan Henderson]

In message <20010305162541.5E74F8A3 at sean.ebone.net>, Sean Doran said:
>Mmmm, socio-psychology meets networking.  Always fun, never understood fully. 
>:)
>
>| It would be useful to know the absolute highest delays that gamers can 
>| tolerate.
>
>Surely this will be somewhat application-dependent?
>
Yes, you'd expect (within networked games) that delay requirements would look 
like shoot-em-up < RPG < chess. It should be possible, however, to come up 
with some general figures, a G.114 equivalent for shoot-em-ups. I'd just like 
something more concrete than figures pulled out of a hat, so if anyone knows 
of any (reasonably) scientific studies please point me at them.

>However, there's probably some literature here and there about
>human reflexes and how fast one needs a result back from a "twitch"
>in order to feel reasonably interactive.   Probably very little
>of that will focus on network impact.
>
Precisely. There is stuff in the VR and physiology worlds about reflexes, but 
it's not clear that this applies to the Internet, where people seem to put up 
with a lot more than they'll admit to in a lab experiment.

>| >FWIW, network games are fascinating examples of interactive applications.
>
>They're also fun.  I've never been big into shoot-em-up games,
>since building the Internet is faster and harder, but some friends
>had me over to play Unreal Tournament with their clan the other week,
>and my eyes were opened a bit.  UT in any event was more sensitive
>to loss and "drop outs" than to stable delay -- for me, anyway, choppy
>updates and missed action was more important and harder to compensate
>for than aiming ahead along the direction the target is seen to be moving.
>
Interesting. I've been concentrating on Half-Life mainly (it seems to be the 
most widely-played game according to tracking sites such as  
http://www.theclq.com/games.asp) but I might have to give UT a go as well.

>| I agree. I'm particularly interested in the multiuser aspects - for example,
> 
>| as you state, there are dynamics which may force users with similar network 
>| characteristics to congregate together.
>
>It turns out that LAN parties are pretty common: people drive across
>Europe to gather together around a hub or small switch, matching up
>as teams in a series of competitions within a broader league.  
>
But this isn't always an option for geographically dispersed groups, so a lot 
of games server operators allow clans to book servers for private games. 
That's why I'd quite like to determine the QoS requirements for applications 
such as these; games players are already spending lots of money on their 
habit, so they should be quite receptive to paying for QoS.

>| Alas, games seem to have been neglected by the networking
>| research community, but hopefully that is changing.
>
>Heh - well, they're sure popular among operators, at least those
>on the operations front, as far as I can tell.  Perhaps that is
>a reflection of a dichotomy between people who are reactive & practical
>versus people who like to plan in advance and understand the theory
>behind things.
>
No comment :)

Cheers,
Tristan