rec.autos.simulators

Hi all!!

With the recent plethora of IPX compatible games released for us to have a
ball with, a couple of questions have cropped up in my mind.

1. Is it necessary to be a Novell CNE in order to be able to write these
games?

2. Why is it that the maximum number of players that can participate in a
network game is only eight? Is it because of some incapabilities with IPX,
or is it bandwidth, or is it driving net-admins nuts, or is it something
else?

I think it would be fantastic being able to race against 25 other
human-controlled cars in an F1 race over a network (are you reading this,
Geoff?) and having 40 players running amok in ultra deathmatch DOOM,
Quake, or whatever ID can think of (Are you reading Michael, John,
Joseph?)

Thanks in advance,

Cameron..

|>Hi all!!
|>
|>2. Why is it that the maximum number of players that can participate in a
|>network game is only eight? Is it because of some incapabilities with IPX,
|>or is it bandwidth, or is it driving net-admins nuts, or is it something
|>else?
|>
I'm just taking a guess here. I most network type game, there would be a game
server somewhere in the network. Clients would just logon to the server if
they ever need to play. So what the client would do is send a move to the server
and get other moves (by other players). The server do most of the processing,
working out the game rules, etc. The client would do most of the display. Now
I believe that with the current crop of network games, there are no servers, so
the client must be the server. This places tremendous processing on your client.
So instead of have 25 people in the game and change DOOM to SNORE, these games
just limit the no. of players. I am not a fan of these first person type game,
so I cannot cite any examples.

|>I think it would be fantastic being able to race against 25 other
|>human-controlled cars in an F1 race over a network (are you reading this,
|>Geoff?) and having 40 players running amok in ultra deathmatch DOOM,
|>Quake, or whatever ID can think of (Are you reading Michael, John,
|>Joseph?)
|>
|>Thanks in advance,
|>
|>Cameron..
|>
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Lee Chuk Munn
SunService Division
Sun Microsystems of California Limited
22/F Shui On Centre
8 Harbour Road
WANCHAI
HONG KONG

Voice: +852 2820 0186
Email: see 'From:'
-------------------------------------------------------------------------------

No. CNE's design, install, and maintain networks. You just need to be a
programmer, with experience on writing network apps.

I would guess bandwidth. DoomII with four players, can sloooooow a
network way down, so 25 players would probably kill it.

I agree. Maybe someday.

Mike

Take a look at Actua Soccer. At my last company we regularly had a 20
player game on the go. It seems to be a self imposed limitation on the part
of the softies that the majority of games only run to 8 players max.
Perhaps it's limitations with the game engine coping with all those
simultaneous players. Who knows?

One thing I do know is that you can bet any organisation that has 20 top
flight PCs so everyone can get in on the action also has a few more PCs
that could act as servers for the game. Maybe it's time to do dedicated
network versions ala Hawaii?

It'd be great :o) I'd never go home.

--
Derek James

Nope ,that's bullshit. All you need is good refernce manual. Or some example-
programs. Can give refs to sites ,where you can get them.
I assume , that is because of speed of the computer. Standart network
bandwidth is 10 mbit/s while modems are 14400 bit/s(about the standart).
It is plenty.
Hmm would be nice , but drivers are slow. When pentuium 120 will become
standart evrywhere, then it will go up 20-40 connections.
Also games have Servers and clients. So if 50 people will connect to a single
486-66, I don't 3d game will go very smooth.
Just my opinion.
Pavel.
---
FEAR-false evidance approves real

(604)595-7289
(604)595-0948 ask for Pavel...
:-)

(I have been out of school for a long time, so please flame me if I
***this up)

Suppose there are n players. If each player make a move, and send that
move to *all* the other players, the amount of traffic grows at the
same general rate as

        n * n

(called n-squared)... in other words, twice as many players is 4 times
the trafic, 4 times the players is 16 times the traffic... 10 times
the players is 100 time the traffic. It grows pretty explosively.

Then there's the handshake problem that is related. If n people walk
into a room, and everyone wants to shake hands with everyone else, but
only once, it turns out the number of handshakes that actually happen
are

        ( n - 2 ) * ( n - 1 )

Which is

        n * n - 3 * n + 2

and still a n-squared growth.

My understanding is that there are better methods of network talk that
don't have n-squared growth. But I could be wrong.

Rob

-------------------------------------------------------------
SOON I WILL BE JAVAMASTER            http://www.racesimcentral.net/~roby

I don't have to be enlightened... I only have to be more
enlightened than *you*
-------------------------------------------------------------

I'm beta testing the (as yet very flaky) Wireplay service here in the UK
and I'm itching to get involved in some multi player racing. As yet, the
only thing that looks at all promising is Nascar. Who knows when (if) it'll
hit our shores?

--
Derek James

In a server based model that wouldn't happen, the server can do relevance filtering.

-(I have been out of school for a long time, so please flame me if I
-screw this up)

-Suppose there are n players. If each player make a move, and send that
-move to *all* the other players, the amount of traffic grows at the
-same general rate as

-       n * n

Only if you send the move to each machine. A general broadcast of the
move would only have 'n' messages. I'm not an IPX programmer, know
little about it and don't know if it allows general broadcast. So
flame Rob if I'm wrong (he asked for it, look up there ^).

--
Ron Whittle

sorry but it's (1/2) * n * (n - 1). Try n=2 people... there should be one
handshake.

However, it is still O(n^2) (n-squared growth), like you said before.

--
-Jim

: However, a potential problem that I see is with the Ether - you tend
: to get this kind of exponential slow down as you add more players
: because of so many more collisions happening (see Binary Exponential
: Backoff).  It would be interesting to see how well a networked game
: would work on a Cambridge Ring where there are no collisions & where
: you could take advantage of the fact that yoyu know how long it will
: take for your data to circulate around the network.

But since Ethernet uses a carrier sense, you ONLY get collisions when
two stations begin to transmit simultaneously.  While this certainly
happens, it has been shown that ethernet is capable to delivering
95% of line speed, or 9.5 Mbit/s, at least.  More than enough for a
game.

However, let's look at the real issue, latency.  Games aren't the
type of application that traditionally have large bandwidth requirements.
They are very picky about packet turn-around tho.  So, let's see...
An ethernet packet is 64-1500 bytes.  Most games don't even use 64 bytes
per packet (DOOM for example).  But, let's be conservative and split the
difference, 700 bytes (way too much, but this is just to prove a point).
If we do the math, we get a theoretical limit of 1785 packets/sec for
700 bytes packets.  If each host needs 20 packets/sec each way (which
is ridiculous because most good dead reconning algorithms don't use
constant 2-way traffic), that still leaves us enough bandwidth to
support ~45 hosts.  And this isn't even considering 100BaseT or the
new 1Gbit/sec ethernet.  Ethernet is up to almost any game anyone
will care to play for a while.  By then, we'll all have ATM to our
houses anyway ;)

Steve

Ethernet is more deterministic than Token Ring is, and it loads cleanly,
without any Binary Exponential Backoff of the application level of the
protocol.  The Binary Exportional Backoff is only used in the case where an
actual PACKET collision occurs, which would require that the carrier sense
part of the protocol had actually failed.  (CS/CDMA)  This would only occur
when the packet preamble collides with another preamble from another card,
which by the nature of signal propagation and the definined maximum length
of the wire in Ethernet, given a scenario of no packet switches or other
devices, you have a possible window of opportunity of about 10 e-6 seconds
for a Carrier Sense failure to actually occur.  What this means is that
once a card has established the preamble on the wire, the packet is
typically guarenteed to be fully transmitted, unless there are cards that
are misfunctioning or the wire has some sort of transmission problem.  What
that breaks down to is that with the interfame spacing, that the network
will actually load up to about 9.6 Mb, with even sharing of the load and
even access.  There are not more collisions, since the cards will not
attempt to transmit where a carrier signal is on the wire.  The only time
that the cards may actually have a collision is in a single phase of a
single 20 M/cycle wave (manchester encoding is used to get to 10 Mbit.)
unencoded wave transmission down the 1000 foot length of the wire.  Since
electricity travels at about 60% of the speed of light, Ethernet is VERY
stable.  So where a collision occurs is where a two cards transmit the
preamble exactly at the same time onto the wire, (not very likely, since
they see the end of the previous packet at slightly different times
anyway).  Of course, when a card fails, or isn't up to specification, or
the wire is not within specification, there are other issues, but a clean
Ethernet runs very, very well.  That's what CS/CDMA is the access method
used in the higher speed fiber optic networks.

Token ring on the other hand requires that the token circulate and be free
in order to add data to the token, and each card clocks the data off the
wire and then back onto the wire.  (At least the standard 4 MBit style..)
So the latency is higher and the throughput is lower for Token Ring.
(Which has been borne out in test after test of server performance on Token
Ring and Ethernet)  

Given the actual fluctuation of Ethernet latency and the actual number of
collisions that exist in a properly wired Ethernet network.  There would be
no discernable difference.

Wilbur

Is there a specialized group to discuss this kind of stuff? Or we just
stick to crowded rec.games.programmer?