Questions[wifi](server)

Consider a Wi-Fi network with one access point and two clients, operating in marginal conditions due to range, etc. Client 1 is communicating with Client 2. Obviously the Access Point (AP) must be in range of both (assuming no fancy mesh modes, etc.) for the network to be deemed available, but does the data actually travel through it?

That is, does the AP receive the packets from one client and rebroadcast them for the other client to pick up, or does Client 2's radio receive the signals directly as they're transmitted from Client 1 and the AP just provides some sort of arbitration and metadata to help them find each other?

I'm particularly interested in how the answer to this would affect the case where the two clients are near to each other and have good radio propagation, but the access point is some distance away.

Has anyone ever seen this before? Note that this happens not only with google.com, but with every domain I try. It's a wireless connection (WEP), but I'm not sure how that would be relevant:

$ curl -v google.com
# This takes about 60s to return
* getaddrinfo(3) failed for google.com:80
* Couldn't resolve host 'google.com'
* Closing connection #0
curl: (6) Couldn't resolve host 'google.com'

$ wget google.com
--2011-11-28 14:44:08--  http://google.com/
Resolving google.com... failed: Name or service not known.
wget: unable to resolve host address `google.com'

$ ping google.com
PING google.com (209.85.148.147) 56(84) bytes of data.
64 bytes from fra07s07-in-f147.1e100.net (209.85.148.147): icmp_req=2 ttl=54 time=136 ms
64 bytes from fra07s07-in-f147.1e100.net (209.85.148.147): icmp_req=3 ttl=54 time=34.0 ms
64 bytes from fra07s07-in-f147.1e100.net (209.85.148.147): icmp_req=4 ttl=54 time=34.3 ms
64 bytes from fra07s07-in-f147.1e100.net (209.85.148.147): icmp_req=5 ttl=54 time=42.5 ms
64 bytes from fra07s07-in-f147.1e100.net (209.85.148.147): icmp_req=6 ttl=54 time=44.7 ms
64 bytes from fra07s07-in-f147.1e100.net (209.85.148.147): icmp_req=7 ttl=54 time=34.5 ms
^C
--- google.com ping statistics ---
8 packets transmitted, 6 received, 25% packet loss, time 7007ms
rtt min/avg/max/mdev = 34.063/54.376/136.026/36.758 ms


$ host google.com
google.com has address 209.85.148.106
google.com has address 209.85.148.147
google.com has address 209.85.148.99
google.com has address 209.85.148.103
google.com has address 209.85.148.104
google.com has address 209.85.148.105
google.com mail is handled by 30 alt2.aspmx.l.google.com.
google.com mail is handled by 40 alt3.aspmx.l.google.com.
google.com mail is handled by 50 alt4.aspmx.l.google.com.
google.com mail is handled by 10 aspmx.l.google.com.
google.com mail is handled by 20 alt1.aspmx.l.google.com.

$ host google.com 192.168.1.201
Using domain server:
Name: 192.168.1.201
Address: 192.168.1.201#53
Aliases: 

google.com has address 209.85.148.103
google.com has address 209.85.148.104
google.com has address 209.85.148.105
google.com has address 209.85.148.106
google.com has address 209.85.148.147
google.com has address 209.85.148.99
google.com mail is handled by 40 alt3.aspmx.l.google.com.
google.com mail is handled by 50 alt4.aspmx.l.google.com.
google.com mail is handled by 10 aspmx.l.google.com.
google.com mail is handled by 20 alt1.aspmx.l.google.com.
google.com mail is handled by 30 alt2.aspmx.l.google.com.

$ cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 192.168.1.201

$ cat /etc/hosts
127.0.0.1       localhost
::1             localhost

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.1.254   0.0.0.0         UG        0 0          0 wlan0
127.0.0.0       127.0.0.1       255.0.0.0       UG        0 0          0 lo
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 wlan0

Basically any application, including Firefox, can't work to do name lookups. What's more, if I take the wifi offline and plug in an ethernet cable, everything is fine.

We've got a Draytek 2829VN Wifi router and I'm wondering how many concurrent connections I should expect a router of this kind to cope with? We are looking to connect 60 iPads!

I'd also be interested in knowing what might happen when it starts to reach capacity?

Not looking for details specifically for this model, but in general.

Thanks!

UPDATE

Thanks for everyone's help!

We ended up going with 3 wired Cisco AP's, sharing a single SSID across 3 channels. The venue already has WiFi running across channels 1,6 & 11 (the default it seems) so we've opted for channels 3, 8, and 13 which seems to be working very well, with around 20 iPads per AP.

The iPads then picked up the signal almost immediately, something they were taking in excess of 2 minutes to do when running on channels 1,6,11 due to interference.

Lesson learned : don't assume that setting up WiFi for large numbers of people is easy!

There are many pages on the web advising the use of wifi channels 1, 6 and 11 only, so that your wifi channels don't overlap.

Obviously this makes sense when you only have your network do deal with, but in most urban areas there are now a plethora of other networks, all using the same channels. In my current location there are about 4 networks on channel 6, and a couple on channel 1.

So my question is: What happens when you get lots of networks on the same channel? Do the intelligently share it? It is better to have two networks on channel 6, or one on channel 5 and one on channel 6?

I was wondering if anybody knew what the maximum string length of a browser's SSID is or where I could go to look for that sort of information. (From a spec of some sort)