[nSLUG] Wireless Router

Daniel Morrison draker at gmail.com
Sun Mar 14 13:57:20 ADT 2010


On 14 March 2010 07:03, George N. White III <gnwiii at gmail.com> wrote:
> On Sat, Mar 13, 2010 at 4:43 PM, Jack Warkentin <jwark at eastlink.ca> wrote:

> 802.11n is backwards compatible with b and g.

Is this true? I don't think a literal interpretation of that sentence
is correct.

Most 802.11n devices also have 802.11b/g capabilties. When operating
in "mixed" mode, a number of 'n' features are turned off in order not
to interfere with 'a/b/g' transmissions, however this reduces the
capabilities of 'n'. When operating in pure 'n' mode, 'a/b/g' clients
on the same frequency will not work (even to a separate wifi router
running 'a/b/g', because 'n' clobbers the bandwidth (see note*). To me
this means the wifi devices are backwards compatible (with help from
802.11n operating in "non-interference" mode) but the 802.11n
specification itself is NOT backwards-compatible.

> 802.1a is 5GHz and is
> a big help if there are already a lot of 802.11 b or g devices nearby.

*note: If I've understood correctly, 'n' can operate in either 2.4GHz
or 5 GHz, so it is possible to get the full capabilities of 'n' while
maintaining either 'a' (5 GHz) or 'b/g' (2.4 GHz) clients.

>> 3. DHCP Reservations/Static Leases
>>
>> I strongly support Michael's stand on this. You want to be able to set
>> up your /etc/hosts file so that you can connect between machines by
>> name, rather than by pinging around until you can discover the current
>> IP address of the machine you want to connect to.
>
> I don't find this necessary, but it is something you will find on the higher-end
> gear.
>
> Service discovery (Zeroconf, Bonjour) allows you to use <hostname>.local
> to connect to systems with DHCP assigned addresses by name.  As long
> as you don't need the fixed IP for external access service discovery should
> be fine for internal networking.
> See: <http://en.wikipedia.org/wiki/Avahi_(software)>

I must say I'm astonished that any wireless router would not offer
static dhcp reservations. IMO that's another reason to get a
Linux-based system -- so it can be customized to do what is possible,
not just what the vendor thinks is necessary!

If avahi/zeroconf/bonjour works for you, then great, use it. But as a
sysadmin I find it mostly yet another annoying broken "feature" that I
have to keep turning off to get the systems configured properly. I
don't really have anything against it, but even when it works, keep in
mind that it is yet another layer of auto-configuration that can go
wrong. (yes, of course static dhcp IP assignments can also go wrong/be
forgotten, but they are relatively simple and easy to understand).

> Many people have come to expect wireless connections to be erratic.
> With proper equipment wireless can be robust.

Yes. Proper equipment and proper expectations, and proper _software_.

I have a laptop in the far corner of my house from my wireless router.
It dual boots Linux/WinXP. In WinXP it drops the wireless connection
every five minutes, and refuses to auto-connect (I have to manually
reconnect). A real pain in the neck. In Linux, I can see that there
are momentary disruptions (transfer speeds go to zero, then resume,
then go to zero again) but the resumption of service is fast enough
that it is usually imperceptible. Linux win!

-D.



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