Point to Point Wireless??

[James Gray]

On Mon, 20 Mar 2006 01:19 am, Arjun Shankar wrote:
> Well, basically, in India a notebook is a luxury (I got mine with a
> loan :)), so a wireless hub is something I cant even dream of buying
> as a student. To get to the point, is there a wireless equivalent of
> connecting two computers directly (like its done with wired NICs)
> without needing a hub? If yes, how? and if not why not?
> Arjun Shankar

Google "adhoc wireless +Linux" (without the "").

Basically 802.11 defines two distinct modes: infrastructure (sometimes called 
"managed") and adhoc modes.  The first mode (infrastructure) uses access 
points where everyone's wireless NICs talk to the access point - hence the 
reason access points are sometimes called wireless hubs. Never refer to an 
access point as a "router" they DO NOT route traffic.  Wireless bridges 
behave like traditional bridges though, and can be loosely described as a 
"router"...but 802.11 does not define any routing per se.  802.11 is layer 1 
and layer 2 only.  Routing typically occurs at layer 3 and sometimes 4.

Adhoc mode does not need an access point and all hosts on the wireless LAN 
talk to each other directly.  There are some pretty big performance penalties 
with adhoc mode and once you exceed around 15-20 hosts on an adhoc network, 
you'll start noticing losses in throughput and increased latency.  Once an 
adhoc network hits around 40 hosts, the network is almost completely 
saturated with "control" messages and there is very little bandwidth left for 
useful data. (Borgia, Gray, & Schreiber "Simulating Ad Hoc Networks", 2005)

However, if you only want to hook up a few machines, you can achieve that in 
Linux with the following stanza in /etc/network/interfaces:

iface wlan0 inet static
    wireless-mode      ad-hoc
    wireless-essid     My-adhoc-network 
    wireless-key       s:eatme
    address            192.168.0.100
    netmask            255.255.255.0
    broadcast          192.168.0.255

Then simply "sudo ifup wlan0" from a command prompt.  Make sure everyone else 
on the adhoc network is using the same IP range, ESSID and key.  BTW, the 
"wlan0" might be different on your machine.  My lappy has an Intel Pro 
wireless which is eth0, and my other lappy had an Atheros-based wifi card 
which was ath0.  So watch that one.

Once all the machines can set up you should be able to ping them and you're 
all set.

A few friends of mine totally geek-out one the train (2 hour commute) and set 
up adhoc networks to play Quake, share files and such.  Works really well!  
Report back if you have problems and I'll see if I can help out :)

Cheers,

James
-- 
No problem is insoluble.
		-- Dr. Janet Wallace, "The Deadly Years", stardate 3479.4
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