Grex Systems Conference

Item 65: Wireless Networking

Entered by ball on Fri Dec 15 00:43:35 2006:

78 new of 122 responses total.


#45 of 122 by keesan on Tue Dec 19 16:37:06 2006:

I seem to need root privileges to do much of anything so I have been running
as root for four years with no problems.  'user' could not use zgv, and when
I typed mutt (telnetted with Windows to linux) I got very loud noise.


#46 of 122 by ball on Tue Dec 19 17:04:02 2006:

Literally a loud noise? I think the only noise you're likely
to hear from a telnet session is the bell, but perhaps if
the speakers were cranked up, that might be surprising.  If
you have to be root all the time, then your unix is broken.


#47 of 122 by gull on Tue Dec 19 20:20:44 2006:

Re resp:43: Some of the PCI adapters sold for use with wireless cards 
are not actually generic PCMCIA slots, but rather adapters specially 
designed for that company's cards.


#48 of 122 by keesan on Tue Dec 19 21:44:39 2006:

The noise sounded like very loud static.  Windows seems to be set up to make
noises on that computer despite my checking off Mute - is there some place
to tell it not to make system noises?  My linux is designed to run as root.
svgalib has problems when used as user, so does Xvesa, then I would need
to give myself privileges to save files to various directories.  Most of the
time I spend doing administration (adding and modifying programs, compiling,
etc.).  


#49 of 122 by ball on Tue Dec 19 23:10:33 2006:

There is something wrong with the MS Windows machine (either
with the hardware, or with the driver software) if it is
making a loud hash noise while you have mute selected.  It
seems as though data that doesn't represent sound is somehow
finding its way to the digital-to-analogue convertor (DAC).

If your Linux is designed to run as root, then I consider
its design broken.


#50 of 122 by mcnally on Tue Dec 19 23:19:05 2006:

 That's the way "Linspire" (formerly "Lindows") is designed to run,
 though I doubt that's the distro she's using.

 I wouldn't want to run that way, but some people do.


#51 of 122 by ball on Tue Dec 19 23:23:47 2006:

/me shudders


#52 of 122 by keesan on Wed Dec 20 01:41:31 2006:

I have the same software on several machines and can easily restore it.  I
am root in DOS, why not in linux?  Win98 also played all the WIndows noises
at the library despite being muted.  How do I turn off Windows noises?  I can
turn off online Opera noises.


#53 of 122 by mcnally on Wed Dec 20 02:06:27 2006:

 >  I  am root in DOS, why not in linux?  

 For the very same reason you shouldn't be root in DOS (which, admittedly
 has no other options) or in Windows (which, nowadays at least, does) --
 that always running at the highest privilege level makes it trivially
 easy for a rogue program to corrupt the entire system.


#54 of 122 by nharmon on Wed Dec 20 03:43:46 2006:

Some of us who have to follow accepted security practices in our work
generally do the same at home because it keeps up our "A" game. On top
of that I consider a lot of the data I keep at home to be fairly
important and I like to see it protected against loss.


#55 of 122 by keesan on Wed Dec 20 20:40:06 2006:

But I don't have any rogue programs and have not had problems in four years
and if I did I would just copy back the software from one computer to another.

Today I am trying to figure out why udhcpc does not work with my small laptop
kernel but does with another, so I tried a third.  Stuck in a wireless card
in the kitchen, forgot to plug in the router, got an IP number and three dns
numbers from some network with signal strength -139dB (noise -156dB) but it
did not last long, went back to signal strength 1/48 to 17/48.  For the 20
seconds it lasted I could go online with two browsers, so all I need now is
to wait for the free county wireless signal, or take the linux computer to
the library instead of windows.  Victory!  (I still need to fix my laptop
kernel to use udhcpc).  I have detected four networks with iwconfig too.


#56 of 122 by cross on Thu Dec 21 00:08:43 2006:

Regarding #55; That you know of, you mean.

In general, running is root is considered bad form.  If you can get away with
it, then great; but don't be surprised if it bites you in the butt one day.


#57 of 122 by keesan on Thu Dec 21 02:12:48 2006:

Where would a rogue program come from and what is it?


#58 of 122 by cross on Thu Dec 21 03:02:59 2006:

It could come from anywhere.  The `rm' command, if used without caution as
root, could become a `rogue' program.


#59 of 122 by ball on Thu Dec 21 03:09:37 2006:

That's a good point:  Running as a user helps to protect you
not just from other systems or people with hostile intent,
but also from yourself.  rm * in the wrong directory is a
great example of that.


#60 of 122 by ball on Thu Dec 21 03:22:30 2006:

It also provides more protection from a userland application
that loses its mind.


#61 of 122 by keesan on Thu Dec 21 04:18:11 2006:

But I have an identical computer next to this one linked by ethernet cable.
And I could also just copy everything to another partition here.  It is a 10GB
drive and my linux fits fine in 1GB or less.  I keep what I have compiled at
a shell account.  


#62 of 122 by ball on Thu Dec 21 05:03:05 2006:

If they're separate partitions on the same disk, or even
seperate disk drives connected to the same computer, then
they provide no significant redundancy (since an errant
program, run as root can simply erase all connected disks).
Having an identical computer connected via a network cable
is a handy thing (I do something similar myself), but if
they're running the same system software, they're going to
share any vulnerabilities that it has.  In your case
replacing the data may be trivial, but for most people that
is probably not the case.  Besides, isn't it a bit like
saying "I don't lock my front door because I have home-
owner's insurance"?


#63 of 122 by maus on Thu Dec 21 05:05:09 2006:

Keesan, I have fat fingered a single "." into "..". The guy who hired me
at my current job has still never lived down a "chmod -R 600 .." instead
of "chmod -R 600 .", which made everything in the entire machine
unreadable by anyone except root and unexecutable by anyone including
root. Had he been running as his normal login, he would have done very
little damage, but because he was using the root login, he and a
colleague wound up having to reimage the server and restore settings and
data from backup, which is a royal P.I.T.A. 


#64 of 122 by cross on Thu Dec 21 14:15:09 2006:

Sindi, you can do what you want.  But like I said, it might bite you in the
ass.  If you don't care, then great, I really have *no* interest in trying
to convince you otherwise, but it is bad form.


#65 of 122 by keesan on Thu Dec 21 16:38:09 2006:

Most of what I do in linux is not doable by user.  The only damage I have done
is crashing things, and e2fsck fixed it all but once (when I think the drive
was bad).  I read email and browse mostly in DOS (kermit, lynx, pine).  And
replacing the contents of a house is a lot different from copying software
between computers, which I do every time I change drives anyway.

I don't want to have to change write permissions on a bunch of directories,
or write only to one directory with subdirectories, wastes time.

I discovered iwlist (on the card that supports it) shows 8 available
connections.  I need to compile a newer pcmcia module for the other card to
work with iwconfig.  I have the source code.  Do I uncompress it into the
pcmcia source code directory and make all again?  Can I make just the one
module and if so how?  I think udhcpc (a small dhcpc) can choose between
connections by address with -r .


#66 of 122 by ball on Thu Dec 21 18:11:29 2006:

I live inside my computer ;-)


#67 of 122 by gull on Thu Dec 21 18:43:56 2006:

Re resp:56: I learned not to run as root when I accidentally typed "rm 
-rf /usr" instead of "rm -rf ~/usr".


#68 of 122 by remmers on Thu Dec 21 19:04:33 2006:

I would be extremely nervous to run as root all the time.  On modern Unix 
and Linux systems, I find that the "sudo" command provides a rational 
middle ground, providing reasonable protection against unfortunate 
accidents while not requiring a full-blown root login every time I want to 
do something requiring administrative privileges.


#69 of 122 by cross on Thu Dec 21 19:21:07 2006:

Sudo has a lot of advantages: among them, it logs commands via syslog.  So
if someone does something mistakenly, there is at least a lot which one can
look at to see what happened.


#70 of 122 by cross on Thu Dec 21 19:26:51 2006:

Regarding #32; I wanted to write more about this last week, but was
tremendously busy.  This is not universally true; in some contexts, a kilobit
is canonically taken to be 2^10 bits.  The wikipedia article, for instance,
includes this interpretation.


#71 of 122 by ball on Thu Dec 21 21:36:09 2006:

S.I. says one k is 1,000.


#72 of 122 by maus on Thu Dec 21 23:07:34 2006:

The problem is that both pow(10,3) and pow(2,10) are correct, depending
on the context. System Internacional uses it to represent the former,
while computers (which 'think' in base-2 rather than base-10) use it to
refer to the latter. As an approximation, they are close, but the
difference does matter. 


#73 of 122 by cross on Thu Dec 21 23:10:58 2006:

That's the great thing about standards: there are so many to choose from.

Why is one kilobyte considered to be 2^10 = 1024 bytes?  Why do disk vendors
give capacities of hard drives measured in 1k = 1000 bytes, when the
operating system views things as power of two block sizes?  Which is more
standard than the other?

I'll grant that the 1,000 bits == 1 kilobit definition is standard, but it
is not universal.


#74 of 122 by ball on Thu Dec 21 23:17:06 2006:

10^3 is k, per SI.  2^10 is K, per longstanding convention.


#75 of 122 by ball on Thu Dec 21 23:18:28 2006:

Disk vendors don't specify disk capacity in K or k.  They
use Gbytes or Mbytes and adhere to the S.I. definitions of
those.


#76 of 122 by cross on Thu Dec 21 23:22:59 2006:

Regarding #74; I don't ever remember seeing that, but maybe I wasn't looking
in the right places.

Regarding #75; Actually, if you want to pick nits, they do: the G or M or K
just refers to 9, 6, or 3 as an exponent for 10.  So, technically, Gbytes are
in the same equivalence class modulo 10.  But my point was that disk vendors
rate their products in terms of powers of ten, not powers of two.  Saying
KB was just convenient, as the kilobyte is essentially the first `real' unit
in common usage after the byte (that is, few people talk in terms of decibytes
or centibytes).


#77 of 122 by maus on Thu Dec 21 23:48:46 2006:

resp:76

Picking more nits, decibyte is 1/10th of a byte. Dekabyte is 10 bytes.
Of course, with word-lengths in powers of 2 (32 or 64), dekabyte is sort
of an awkward amount of data. 


#78 of 122 by cross on Thu Dec 21 23:54:01 2006:

My bad.


#79 of 122 by ball on Fri Dec 22 00:22:44 2006:

Re #73: k != K


#80 of 122 by cross on Fri Dec 22 00:29:21 2006:

Like I said, that's the first I've heard of that.  Got a citation?


#81 of 122 by ball on Fri Dec 22 00:36:32 2006:

K != k just as M != m (M is 1,000,000 and m is 0.001).


#82 of 122 by cross on Fri Dec 22 00:37:06 2006:

Ah, I see what you mean now.  I thought you meant K = 2^n while k = 10^n or
something.  Yes, you are right.


#83 of 122 by ball on Fri Dec 22 00:38:34 2006:

Apparently the International Electrotechnical Commission
(whoever they are) want us to use "Ki" in place of K for
1,024.  Computer people have been using K for 1,024 for a
very long time though.


#84 of 122 by ball on Fri Dec 22 00:39:20 2006:

Re #81: 1K = 1,024   1k = 1,000.


#85 of 122 by ball on Fri Dec 22 00:39:39 2006:

Erm, that was Re #82 ;-)


#86 of 122 by cross on Fri Dec 22 00:41:14 2006:

Regarding #84; You know, I've never heard that before.  Like I said, do you
have a citation?


#87 of 122 by ball on Fri Dec 22 00:43:20 2006:

I'll have a rummage for one.


#88 of 122 by cross on Fri Dec 22 00:44:23 2006:

This is interesting:
http://en.wikipedia.org/wiki/Kibibit

They seem to use ``Kib'' or ``Kibit'' (with a capital K) instead of ``Kbit''
or ``Kb.''  They do acknowledge that ``kilobit'' can be either 2^10 or 10^3
depending on context.


#89 of 122 by cross on Fri Dec 22 00:48:30 2006:

This is also interesting:
http://en.wikipedia.org/wiki/Binary_prefix

Note that they say that in the SI system, `K' (capitalized) stands for Kelvin,
as a unit of temperature, and `k' (lowercase) only stands for `kilo.'  They
say that outside of SI, K and k are mostly interchangable, and can refer to
either 2^10 or 10^3, as I had originally said.  To wit:

'The one-letter abbreviations are identical to SI prefixes, except for "K",
which is used interchangeably with "k" (in SI, "K" stands for the kelvin, and
only "k" stands for 1,000).'

However, they do say that as of 2005, the binary meanings are deprecated.


#90 of 122 by ball on Fri Dec 22 00:53:17 2006:

k (as a multiplier prefix) should only ever be used to mean
1,000.  Everywhere I've ever worked or studies, K has been
capitalised to differentiate it from k.  Telecomms people
talk in terms of kbits/sec, and mean 1,000 bits.  Computer
people talk in Kbytes and mean 1,024.  It's not rocket
science ;-)


#91 of 122 by ball on Fri Dec 22 00:58:49 2006:

Here's an example of K from a PDP-11 manual...
http://pdos.csail.mit.edu/6.828/2005/pdp11/pdp11-40-000009.html


#92 of 122 by ball on Fri Dec 22 01:12:21 2006:

Here's a KIM-1 manual from 1976...
http://users.telenet.be/kim1-6502/6502/usrman.html


#93 of 122 by mcnally on Fri Dec 22 01:12:34 2006:

 re #90:  You're right that "it's not rocket science", but
 it's not universally or consistently applied, either, which
 means making assumptions based on the use of "k" or "K" is
 dangerous if you need better than approximate numbers.


#94 of 122 by ball on Fri Dec 22 01:16:36 2006:

It's been consistently applied in my experience, but it's
true that a few people don't use it correctly.


#95 of 122 by ball on Fri Dec 22 01:21:19 2006:

Take a random sample of computer manuals, text books (I hope
they're right!) or EPROM / SRAM data sheets.  K = 1,024 is a
long-standing convention.


#96 of 122 by cross on Fri Dec 22 01:55:54 2006:

Yes, but you were talking specifically about K = 1024 and k = 1000, and in
neither of the two references that you posted can I find such a distinction.
Everyone knows that most computer manuals refer to K as 2^10 = 1024.  Your
claim was that they also refer to k as 1000, which is not universal, and in
fact, is a convention I've never heard of before, and is not supported by your
evidence.

If telecom people refer to kbits as 1000 bits, that's great, but what McNally
says is true: if you want to be exact, you've really got to specify.


#97 of 122 by ball on Fri Dec 22 02:01:40 2006:

k is 1,000 because of S.I.  (km, kg, kW etc.)  It's only
necessary to specify because some people seem underinformed.


#98 of 122 by cross on Fri Dec 22 02:06:58 2006:

*sigh*  It's not being underinformed, Andy, it's recognizing that standards
aren't universally followed.  I don't know how to explain it better than that.
Really, though, it's true: not everyone follows the same standards.


#99 of 122 by ball on Fri Dec 22 05:20:23 2006:

Never mind.  Let's talk about wireless networking.  My next
wireless networking task is to find a PCI 802.11g adaptor
that works with NetBSD.  This could take a while.


#100 of 122 by keesan on Fri Dec 22 18:29:31 2006:

How are you searching, in BSD online discussions?


#101 of 122 by ball on Fri Dec 22 18:58:57 2006:

I'll probably start with the man pages for common device
drivers such as ath(4) and perhaps wi(4).  Hopefully I'll be
able to find a card that has an appropriate chipset.


#102 of 122 by keesan on Fri Dec 22 19:20:38 2006:

There are lists of linux-compatible pcmcia cards.  Why don't you search on
BSD PCI wireless?


#103 of 122 by ball on Fri Dec 22 23:06:52 2006:

The man pages that I mentioned include lists of cards that
are supposed to work.  Sadly some manufacturers will change
the chipset in a product without changing the model number
so it can be something of a lottery.


#104 of 122 by gull on Sat Dec 23 03:25:11 2006:

Re resp:75: My impression is that the computer world pretty universally 
used K=1,024 until marketing types realized they could put a bigger 
number on hard disk packages if they used K=1000.  For a while they 
tried to avoid confusion (and presumably false advertising claims) by 
using the phrase "million bytes" instead of "megabytes."


#105 of 122 by ball on Sat Dec 23 03:32:31 2006:

I never saw them use K=1,000, but I did see them use
M=1,000,000 which makes sense in the context of S.I.  They
could have excusably used k=1,000 but I never saw that
either.


#106 of 122 by ball on Sat Jan 20 01:51:43 2007:

I now have a D-Link DWL-G510 802.11g PCI wireless network
adaptor working under NetBSD-current.


#107 of 122 by keesan on Sat Jan 20 02:00:10 2007:

What module(s) and what else did you need to do?


#108 of 122 by ball on Sat Jan 20 03:07:06 2007:

I didn't use any modules, but I had to upgrade to NetBSD 4
which is not quite released as stable yet (it's in Beta
testing).  My kernel includes the ath(4) driver and for some
reason that I'm not clear about yet, bpf (the Berkeley
packet filter) was also required.  I have to launch a thing
called wpa_supplicant because the wireless network uses WPA,
which is supposedly less insecure than WEP.  The usual
procedure for launching the supplicant didn't work for me,
so as a temporary measure I launch it from the rc.local
script. Hopefully that will be fixed before 4.0 is released.


#109 of 122 by gull on Sat Jan 27 21:42:33 2007:

It annoys me that some Linux distributions no longer have an rc.local
script.  There are some applications where creating a full SYSV init
script is major overkill.


#110 of 122 by dtk on Mon Jan 7 03:28:37 2013:

Do you include SATCOM in the list of wireless networking 
techniques/technologies? When I deploy in the wake of natural disasters,
I  am responsible for backhauling unclassified voice and data
communications  over a satellite link, as well as management and
maintenance of the  solution.  -DTK 


#111 of 122 by cross on Wed Jan 9 00:01:36 2013:

Sure!  Sounds reasonable to me.


#112 of 122 by dtk on Thu Jan 10 19:49:05 2013:

Probably like a less cool version of the rig your brothers took out to
the  mountains or the sandbox.  -DTK 


#113 of 122 by ball on Sat Jan 12 16:41:28 2013:

Re. #110: That qualifies.  Is that done using VoIP
  or something else?

It's telling that even though years have passed
since I asked the question, adding a NetBSD host
to a WiFi network is still awkward to the point
where I tell people not to bother.


#114 of 122 by dtk on Sat Jan 12 17:58:08 2013:

We use VoIP phones, connecting back to a phone switch at the HQ. The
phones  use lightweight codec-specific signalling, common to both the
phones and the  switch. Nothing terribly novel. 


#115 of 122 by ball on Sat Jan 12 23:00:39 2013:

Is latency much of an issue with the satellite link or is
that better with today's LEO birds?


#116 of 122 by dtk on Sun Jan 13 01:19:57 2013:

We do not bounce off a LEO bird; they move too much. Instead, we bounce
off  of a geostationary bird. We set expectations about latency, and
people adapt  pretty quickly to the latency, as long as it is
consistent. Jitter is your  big killer, not delay. Oh, and SAA on Cisco
gear, or SmokePing on UNIX (or  Linux) is absolutely your friend,
followed closely by any NetFlow analyzer  you can cope with. 


#117 of 122 by ball on Sun Jan 13 01:58:54 2013:

I'll ask the packet pushers what SmokePing is.


#118 of 122 by dtk on Sun Jan 13 13:44:24 2013:

http://oss.oetiker.ch/smokeping/


#119 of 122 by cross on Sun Jan 20 02:02:09 2013:

resp:115 Latency is almost always an issue for satcom.  Pushing on Ka or X
band to geo-sync/geo-stationary is going to be slow because, well, the speed
of light isn't just a good idea, it's the law.  :-)

I've never had great luck with LEO for anything.  Maybe DAMA voice, but I
don't recall what birds those were bitting.


#120 of 122 by dtk on Fri Jan 25 22:06:42 2013:

Here here. GEOS is great for resilience, and as long as you can tolerate
 delay, you can go anywhere in its shadow. That said, it takes people a 
while to get used to the delays involved in a voice call, but as long as
 the delay is pretty consistent (i.e. low jitter), people adapt. 

Oh, and for the fans following along at home, remember that the speed of
 light in the atmosphere is a lot slower than the speed of light in a 
vacuum. 

I never tried using a LEO-provider; having to track a bird that is in 
motion relative to your frame of reference either requires the dish to 
be in constant motion, or  accept drop-offs frequently. Neither seems 
like much fun, and not worth the small improvement in round-trip-time. 


 -DTK


#121 of 122 by cross on Sat Feb 9 18:18:26 2013:

Indeed.  It's a pain in the butt.


#122 of 122 by tod on Fri Jan 27 15:08:30 2017:

re #114
Back in the stone ages, we used analog phones through a multiplexer over
VHF.  VOIP is a very specific protocol overhead for packet node sites.
I haven't looked at Network44 in years, though.


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