Arranging a LAN Party for 500-2500 people

Hi Im going to arrange a Lan Party for 500-2500 people. I've done some research, but Im still not sure what to aim for in the networking section.

This is my approach as is:

1 Backbone switch with between 100-500 Gbps total switching capacity depending on the number of users (as said before 500-2500)
For each group of 16 people there will be a 10/100 manageable switch with double gigabit uplinks, for connection to the backbone.

I still don't know what to aim for in the routing department, because Internet access will be needed.

What's the difference between a router and a Layer-3 switch?

I'd appreciate any help!
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I've been organising lanparties for over 6 years now with up to 1600 people.
This is my view:

The backbone of a lanparty is important, but it's not thé most important thing; your client switches' internal backbone (aka backplane) is just as important !

When running a lanparty network with ~1000 users, we usually get peaks of up to 30Gigabit on the backbone switch of the network. Translate this into 2500 users on a single VLAN (layer2), you should be getting around 100Gbps traffic on your backbone.

You are going to have problems with broadcast though, as any lanparty on this scale has. Your users should be able to cope, but anybody with a 10mbit network card will be fubar. You could divide your lan in VLANS or (with a layer3 switch) make routing groups, but the problem here is that it limits your lan-game broadcast in most games (aka: only half the hall will see the servers).

We provide 1Gbit (fullduplex, so 1 up and 1 down) to every client switch we have; client switches have between 16 and 24 people on them. If you have enough ports (and cables) on your backbone switch, you could ofcourse upgrade this to 2Gbit full duplex. In general, this is not necessary, except if you expect *a lot* of Linux-distro downloading ;-) going on.

Your backbone switch should have at least as many gigabit ports as you have client switches (x2 if you plan to use dual gigabit uplinks). Your backbones backplane should be at least double the amount of gigabit ports it has (128ports = 256Gbit). Also, it's not all about gbps here, it's also about pps (packages per second). If you have a backbone switch with (example) 10gbit backplane but it can only deliver 1mill packages per second, then you are screwed; 1mill x 1500bytes (max size of tcp ip package) = 1.5bill bytes/secs = 1.5gbit real usable backplane speed. Yes, somebody will tell you about Jumbo Frames and Gigabit, but this only works for end-points that actually use jumbo frames. Your clients (= gamers) are on 100mbit, so they are not using Jumbo Frames.

If you want to give your people internet access, you can use different approaches. I suppose you will want to be able to throttle bandwidth and give the users firewalled access to the internet, so i propose using a Linux or hardware firewall box.
how you implement this firewall is up to you; you can use a Layer3 switch and set 1 port to be the route to "outside", which will then go into the firewall and onto the internet.

or you could just set the firewall/router up on the lan with a public lan-ip and make people use it as their 'default gateway' (you could set this in your dhcp options if you are not using static ip addressing).

Couple of hints on the internet access:
- do not give your firewall the IP or 192.168.x.1 or 172.16.x.1. These IPs are too commonly used in home-setups, which means there's a phat reason somebody will be interfering with your routing when the lanparty starts up. Set the IP to something like
- THROTTLE STEAM TRAFFIC. This is a major issue. Either you disable Steam, but your users will complain (trust me on this ;)), or you throttle it, or, if you are multihomed (best solution) you give it a completely seperate connection (ports 27000 - 27200 should do).
- Use an Internal Proxy Server. Your internet provider may be providing you with a 1Gbit+ connection, it doesn't matter, you *have to have* an internal proxy server. This will increase the internet experience of the users on your lanparty with a magnitude of 10. Even if you have a 10mbit internet connection, every user will be able to download the latest gaming patches at 10mbyte/second if you install an internal proxy server. Your internet bandwidth will greatly benefit from the proxy server aswell, ofcourse. With 1000 users we have about 100Gigs of HTTP traffic in 48 hours, 30 Gigs of which actually comes from the internet and 70 Gigs coming from the internal proxy server!!
- Think about what you are going to do with MMO(R)PG access. A lot of people are playing an MMPOG these days and they don't like to be cut of for 48 hours. Give them a seperate connection or throttle these games' bandwidth, don't just shut them out.
- If you want your users to access IRC (Quakenet comes to mind), make sure you made arrangments with the IRC Operators, or, if your inet provider is a cool one and you get your lines way in advance, setup a seperate temp node (some networks allow this, Quakenet being one of them). This way your users are sure to be able to connect and you are not killing the IRC network in question. Most networks will K-line your line if you haven't made arrangments with them in advance.

I hope this helps a bit, if you have any more questions feel free to ask ;-)


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>What's the difference between a router and a Layer-3 switch?
Hi bjqrn,

Function wise no difference, they both route packets.  But speed-wise, a L3 switch is implied to be faster.

bjqrnAuthor Commented:
Thanks for the response!

Does this look like a decent approach?
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Im not going to comment about management,

PC your design. looks pretty good
If you use decent network cabling (CAT5 SFTP, CAT6) then you don't need repeaters until you reach 100m.

Otherwise the diagram looks pretty good indeed
bjqrnAuthor Commented:
About the router, will a computer acting as a router be sufficent, or will I have to invest in an expensive hardware one?
While organising lanparties of up to 1600 people, we have never used a hardware router, we have always used one (or several, depending on the internet configuration) Linux routers.

A debian box with an unstable distro will work very well for you.

We have been using an AMD Athlon 750Mhz with 256Mbyte ram acting as a firewall/router. However, the specs of the proxy server are a little bit more aimed at performance: Dual Athlon MP System with 2Gigs of RAM and a 36Gig SCSI 10k rpm disk (as webcache) with 128mb cache on the SCSI controller. This is way more important; the linux kernel can perfectly well route at wirespeed on a subpar (according to todays standards) server.
bjqrnAuthor Commented:

But when using a proxy server, will people be able to play games on the Internet without setting the proxy server manually in the game or installing some application?
Most games do not use the HTTP protocol, hence they won't even notice it if they are playing games.

However, what we like to do is redirect *all* known proxy server IPs to the internal proxy servers, so that 80% of our users don't even have to setup their proxy (almost all Belgian providers *require* you to fill in the proxy server; since we are redirecting all traffic going to these IPs on port 8080 to our internal proxy on port 8080, these users are automatically proxied by our proxy server).

If you don't want your users to "go thru the hassle to" type in their proxy server address and port, you can use transparant proxying; most layer3 switches have this feature, just have to configure it. If you don't want to use your switches for this, you can redirect all outgoing traffic on port 80 to the internal proxy server. This is a completely transparant process for your users.
Watch out, however, for MSN; MSN over Proxy can kill your proxy if you don't know what you are doing when setting up transparant proxies.
bjqrnAuthor Commented:

Can you explain the MSN problem a bit further?
MSN tries to connect to the MSN servers first, using port 1653 (this might be of, i can not check this now).
if this does not work, it'll try connecting thru port 80 (tcp).
and if that doesn't workt, it'll try using the proxy server set in in Internet Explorer.
(your user can also manually type in the proxy server address and port in MSN properties).

This will dump a massive load on your proxy server, as this is a persistant non-cacheing connection which will hassle your proxy server every 5 milliseconds.

make sure your user can only use the CONNECT commando on your proxy server (i have to check my own squid settings, don't know by heart) so they can not connect to anything else but WEBservers.
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