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mm
04-06-08, 02:33 PM
Does every wireless g router also transmit b?

If transmission speed is not a concern (because even slow is pretty
darn fast), should he buy a b card that is available, instead of a g
card that might never be available (It's a 10-year old Mac), and will
it likely work everywhere a g card does?



In another thread I wrote a lot, probably more than those in this
group wanted to read, about b vs. g cards.

A couple months ago I was on a trip with my first laptop and a
wireless b card,(generic but using prisma software, and I learned the
maker too. If it matters, I'll find it.)

It worked fine in a couple netcafes, but I also stayed at a dorm and
there it didn't work. The guys told me they were using g, and I
should buy a g card. Which I did. (a D-link b/g card) The software
interface was more comprehensive and seemed to support a lot more
features, but the card itself rarely worked**. I don't think the b
card ever worked, but all in all, I'm still asking, are there routers
that transmit g but not b.

For now, my friend is planning to use his Mac wirelessly, if possible,
at his brother's, who may not know what he is transmitting, but there
are a lot of other places too that he might want to use it.


**After the second card didn't work, the guy in charge let me unplug
the community computer, rarely used, and plug the cable straight into
my laptop, which worked fine.

If you are inclined to email me
for some reason, remove NOPSAM :-)

That Bloke
04-06-08, 02:47 PM
Wireless "g" routers can be set to connect with "b" and "g" clients or "g"
clients only. By default they communicated with both.

"mm" <NOPSAMmm2005@bigfoot.com> wrote in message
news:6o8iv3hl0dn6msqn5i538hsmc5dgm0g845@4ax.com...
> Does every wireless g router also transmit b?
>
> If transmission speed is not a concern (because even slow is pretty
> darn fast), should he buy a b card that is available, instead of a g
> card that might never be available (It's a 10-year old Mac), and will
> it likely work everywhere a g card does?
>
>
>
> In another thread I wrote a lot, probably more than those in this
> group wanted to read, about b vs. g cards.
>
> A couple months ago I was on a trip with my first laptop and a
> wireless b card,(generic but using prisma software, and I learned the
> maker too. If it matters, I'll find it.)
>
> It worked fine in a couple netcafes, but I also stayed at a dorm and
> there it didn't work. The guys told me they were using g, and I
> should buy a g card. Which I did. (a D-link b/g card) The software
> interface was more comprehensive and seemed to support a lot more
> features, but the card itself rarely worked**. I don't think the b
> card ever worked, but all in all, I'm still asking, are there routers
> that transmit g but not b.
>
> For now, my friend is planning to use his Mac wirelessly, if possible,
> at his brother's, who may not know what he is transmitting, but there
> are a lot of other places too that he might want to use it.
>
>
> **After the second card didn't work, the guy in charge let me unplug
> the community computer, rarely used, and plug the cable straight into
> my laptop, which worked fine.
>
> If you are inclined to email me
> for some reason, remove NOPSAM :-)

mm
04-06-08, 03:16 PM
On Sun, 6 Apr 2008 20:47:09 +0100, "That Bloke" <auchenblae@aol.com>
wrote:

>Wireless "g" routers can be set to connect with "b" and "g" clients or "g"
>clients only. By default they communicated with both.

That makes sense. I should have asked the guy at the dorm to turn on
b, if it was actually not on.

There were 5 or 6 or more other people who were using the wireless
with no troubles. I don't know why I had problems, but I won't be
there again for at least a year, maybe never.

At the time I was confused -- I seem to forget things quickly since i
turned 50 -- and thought it was the need to enter a password that
required me to get the new pc card. At the netcafes, no password was
required. And I knew the card that came with my laptop was an old
one. (Heck the whole computer was iirc 93 dollars on ebay, including
30 dollars for shipping, but it worked fine in every other way, except
maybe the microphone jack doesn't work, but the built-in mike does.)



>"mm" <NOPSAMmm2005@bigfoot.com> wrote in message
>news:6o8iv3hl0dn6msqn5i538hsmc5dgm0g845@4ax.com...
>> Does every wireless g router also transmit b?
>>
>> If transmission speed is not a concern (because even slow is pretty
>> darn fast), should he buy a b card that is available, instead of a g
>> card that might never be available (It's a 10-year old Mac), and will
>> it likely work everywhere a g card does?
>>
>>
>>
>> In another thread I wrote a lot, probably more than those in this
>> group wanted to read, about b vs. g cards.
>>
>> A couple months ago I was on a trip with my first laptop and a
>> wireless b card,(generic but using prisma software, and I learned the
>> maker too. If it matters, I'll find it.)
>>
>> It worked fine in a couple netcafes, but I also stayed at a dorm and
>> there it didn't work. The guys told me they were using g, and I
>> should buy a g card. Which I did. (a D-link b/g card) The software
>> interface was more comprehensive and seemed to support a lot more
>> features, but the card itself rarely worked**. I don't think the b
>> card ever worked, but all in all, I'm still asking, are there routers
>> that transmit g but not b.
>>
>> For now, my friend is planning to use his Mac wirelessly, if possible,
>> at his brother's, who may not know what he is transmitting, but there
>> are a lot of other places too that he might want to use it.
>>
>>
>> **After the second card didn't work, the guy in charge let me unplug
>> the community computer, rarely used, and plug the cable straight into
>> my laptop, which worked fine.
>>

If you are inclined to email me
for some reason, remove NOPSAM :-)

Bill Kearney
04-06-08, 09:11 PM
>>Wireless "g" routers can be set to connect with "b" and "g" clients or "g"
>>clients only. By default they communicated with both.
>
> That makes sense. I should have asked the guy at the dorm to turn on
> b, if it was actually not on.

If it's off then it should stay off. Why leave B running and burden the G
network with having to take extra effort to handle the slower signal?

Get a G-capable card. They're cheap enough.

mm
04-07-08, 02:19 AM
On Sun, 6 Apr 2008 22:11:19 -0400, "Bill Kearney"
<wkearney99@hotmail.com> wrote:

>>>Wireless "g" routers can be set to connect with "b" and "g" clients or "g"
>>>clients only. By default they communicated with both.
>>
>> That makes sense. I should have asked the guy at the dorm to turn on
>> b, if it was actually not on.
>
>If it's off then it should stay off. Why leave B running and burden the G
>network with having to take extra effort to handle the slower signal?

To save me 50 dollars.
>
>Get a G-capable card. They're cheap enough.

Where I was they were 50 dollars. And hard to find. It wasn't in
the US.

If you are inclined to email me
for some reason, remove NOPSAM :-)

seaweedsl
04-07-08, 01:05 PM
What Bill is saying, I think, is that as a network administrator, it's
often not efficient or appropriate for a local network to use B.
Your needs as an individual may be different, but you have to play
well with the group!

A big issue with B - and this is what you may be remembering from the
dorm - is that very few B cards can handle the newer WPA security.
In our system, for example, we use WPA (WEP is not secure) but one pc
with a B card only did WEP. It was not worth it to compromise the
security of the whole group just to let him on. We found him an
adapter.

I had an Orinoco classic B card that would do WPA security once I
found the proper firmware. There were 10 versions that did not do WPA
and one that did. So it's possible, just not likely.

If you need to travel and connect in various places, then you want
G.

Steve

msg
04-07-08, 03:15 PM
seaweedsl wrote:

<snip>
> A big issue with B - and this is what you may be remembering from the
> dorm - is that very few B cards can handle the newer WPA security.
> In our system, for example, we use WPA (WEP is not secure) but one pc
> with a B card only did WEP.

802.11b has distinct coverage advantages, and often greater channel
capacity in consumer-grade access points. No one should seriously
rely on embedded security in those products, WEP or WPA; a VPN
(IPsec for example) solution makes more sense and scales better
in a public (campus/dorm) setting.

Michael

mm
04-07-08, 07:16 PM
On Sun, 6 Apr 2008 22:11:19 -0400, "Bill Kearney"
<wkearney99@hotmail.com> wrote:

>>>Wireless "g" routers can be set to connect with "b" and "g" clients or "g"
>>>clients only. By default they communicated with both.
>>
>> That makes sense. I should have asked the guy at the dorm to turn on
>> b, if it was actually not on.
>
>If it's off then it should stay off. Why leave B running and burden the G
>network with having to take extra effort to handle the slower signal?

Maybe I should add that this dorm had about 37 people, maybe 10 of
whom had laptops, and probably no more than 5 were ever running at one
time. Plus they had on the same line a VOIP phone used less then an
hour a day, and 2 desk computers, each of them used less than an hour
a day. So the network was nowhere near its capacity.

I also take issue with the words "burden" and "extra effort". I know
it's common to anthropomorphise machines and electronics, but when
they don't really expend extra effort (or struggle, as I read
somewhere else). They do what they have the power to do, and if they
can't do all that is wanted, the slow down, or stop something. Maybe
sometimes they burn out, break, but that wouldn't happen in this
situation.

>
>Get a G-capable card. They're cheap enough.


If you are inclined to email me
for some reason, remove NOPSAM :-)

mm
04-07-08, 07:22 PM
On Mon, 7 Apr 2008 11:05:19 -0700 (PDT), seaweedsl
<seaweedsteve@gmail.com> wrote:

>What Bill is saying, I think, is that as a network administrator, it's
>often not efficient or appropriate for a local network to use B.
>Your needs as an individual may be different, but you have to play
>well with the group!

Maybe, but I knew this group personally, and we were all fraternal in
our attitudes to each other. Perhaps they were not technical enough
to realize that g could be running and b could run too if it was
turned back on, but if they had known that, they would have told me to
ask the guy who ran things.

But when they told me I needed g, I went out and got it. I don't
think I asked the network guy if that was what I should do, and I know
I didn't ask him if he could turn b back on. He never mentioned the
b-g issued.

Also, I don't think security was really an issue.

I was there for 7 weeks, but other people came and went. A few of them
with laptops. I won't be back any sooner than next March, and
probably not even then. But if I write him or talk to him, I hope I
ask him about all this.

Thanks for the technical stuff.

>A big issue with B - and this is what you may be remembering from the
>dorm - is that very few B cards can handle the newer WPA security.
>In our system, for example, we use WPA (WEP is not secure) but one pc
>with a B card only did WEP. It was not worth it to compromise the
>security of the whole group just to let him on. We found him an
>adapter.
>
>I had an Orinoco classic B card that would do WPA security once I
>found the proper firmware. There were 10 versions that did not do WPA
>and one that did. So it's possible, just not likely.
>
>If you need to travel and connect in various places, then you want
>G.



>Steve
>


If you are inclined to email me
for some reason, remove NOPSAM :-)

Jeff Liebermann
04-07-08, 10:46 PM
On Sun, 06 Apr 2008 15:33:13 -0400, mm <NOPSAMmm2005@bigfoot.com>
wrote:

>Does every wireless g router also transmit b?

The default is to enable 802.11b compatibility. I sometimes turn it
off.

The problem with "b" is not speed. It's the air time it occupies.
Data sent at 1Mbits/sec, the slowest 802.11b speed, occupies about 8
or 9 times as much air time as the same data sent at 6Mbits/sec, the
slowest 802.11g (OFDM) speed. If the airspace is saturated with a
large number of users, 802.11g can ideally handle 8 times as many
users, assuming they're running at the slowest speed (a good
assumption as multiple collisions will cause the access point to
switch to the slowest speeds in an attempt to recover).

There are other problems with 802.11b. With 802.11b compatibility
enabled in the wireless access point, all management packets and
broadcasts are sent at the slowest (and longest) 1Mbit/sec speed. Turn
off 802.11b compatibility, and 802.11g sends them at 6Mbits/sec, the
slowest 802.11g speed.

802.11b also has problems dealing with reflections, multipath, and
frequency selective fading. 802.11g OFDM modulation is far more
resistant to these problems. One would assume that this would not be
a common problem, but I'm finding it all too common.

For example, one of my coffee shop customers is in an octagon shaped
brick building. The place is one big mess of reflections. It's even
difficult to hear onself talk through all the noise and echos. I was
getting erratic download speeds and even some disconnects, for no
obvious reason. Monitoring the wireless router, I found far too many
users connecting at 802.11b speeds. I assumed that this was caused by
interference and reflections. So, I just turned off 802.11b
compatibility. The disconnects instantly ceased, and the erratic
performance was hugely reduced. So were the complaints.

I assumed that there would be problems with users having only 802.11b.
So, I hung up a small sign, under the "we have free wi-fi" sign, that
announced the 802.11b is not supported. There were a few complaints,
that I "solved" by explaining why they should buy a better wireless
adapter. There was also one issue that caught me by suprise. Many
802.11g USB dongles revert to 802.11b only mode if shoved into a USB
1.1 port. The device can easily do 802.11g speeds, but the authors of
the device drivers seem to think that flow control is evil, and that
the wireless speed should be slowed down to match the interface speed.
I can see the logic, but this has given me problems with some users.

There are also some PDA's that do not support 802.11g. For example,
my Verizon XV-6700 only does 802.11b, but does to WPA encryption.
There are other PDA's and cell phones with similar configurations.

At this time, some of my wireless routers have 802.11b enabled, while
others have it turned off. It varies by location, owner politics, and
class of users. If it's a high traffic and high user count system,
802.11b is OFF. If it's light use, then I leave it on.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

seaweedsl
04-08-08, 04:14 PM
On Apr 7, 3:15 pm, msg <msg@_cybertheque.org_> wrote:

> 802.11b has distinct coverage advantages, and often greater channel
> capacity in consumer-grade access points.

Greater channer capacity? In that B can handle more clients per
channel? That seems to be the opposite of what I hear. I admit
that I'm just parrotting what I've learned from the discussions on
this forum, so if there's more to it, then please elaborate.

As far as coverage advantages - are you referring to the greater
transmitting power listed for B? It seems like Jeff disabused me of
that interpretation once already but I forgot the details.


No one should seriously
> rely on embedded security in those products, WEP or WPA; a VPN
> (IPsec for example) solution makes more sense and scales better
> in a public (campus/dorm) setting.
>

What are the security problems in WPA beyond cracking weak
passwords ? I have not heard...

WEP, on the other hand is now well known to be crackable. You are
lumping them both together?

Perhaps what you are saying is that if one is connected to a "hostile"
LAN like a coffee shop, then wireless security does not protect one
from threats within that LAN? And in such cases, VPN to a non-
hostile (if you have one) LAN is best?

That makes sense. Sort of like saying that a deadbolt will not
protect you from strangers already in your house. But that's not to
say that there's no reason to lock your doors ! Or that we shouldn't
use a good deadbolt instead of an easily opened door latch. Or that
administrators don't prefer to control who is allowed in the LAN.

Appreciate any clarification. Since I'm responsible for the security
of a small group sharing a connection, I want to know if there's
something further I should be doing besides using strong pw WPA.
Everyone within is trustable - a friendly LAN, if you will.

Steve

msg
04-08-08, 11:18 PM
seaweedsl wrote:
> On Apr 7, 3:15 pm, msg <msg@_cybertheque.org_> wrote:
>
>
>>802.11b has distinct coverage advantages, and often greater channel
>>capacity in consumer-grade access points.
>
>
> Greater channer capacity? In that B can handle more clients per
> channel? That seems to be the opposite of what I hear. I admit
> that I'm just parrotting what I've learned from the discussions on
> this forum, so if there's more to it, then please elaborate.

I just meant that for a given LAN PHY bandwidth, more 802.11b
connections could be aggregated at 11 Mbps than at 54 MBps
(unrelated to 'client' connections), assuming max rates in
both formats. Capacity is obviously dependent on available
resources in the access point/router such as available ram
for buffers and tables and processing speed of the cpu.

> As far as coverage advantages - are you referring to the greater
> transmitting power listed for B? It seems like Jeff disabused me of
> that interpretation once already but I forgot the details.

Jeff says that OFDM is more robust, and perhaps the shorter
packets at higher speeds suffer less from destructive multipath
interference, but I have memory of analyses that show 802.11b to be
generally more robust in open-air settings. He also says that
slower OFDM speeds compared against equivalent DSSS speeds provide
superior channel capacity; I have no experience to evaluate this.

> No one should seriously
>
>>rely on embedded security in those products, WEP or WPA; a VPN
>>(IPsec for example) solution makes more sense and scales better
>>in a public (campus/dorm) setting.
>
> What are the security problems in WPA beyond cracking weak
> passwords ? I have not heard...
>
> WEP, on the other hand is now well known to be crackable. You are
> lumping them both together?

Just a philosophy; in a setting larger than an informal group, especially
where participants are not entirely trusted, use the best security
available at the least cost -- e.g. a stand-alone router based on
a secure o/s that can be configured and sized to the requirements of
the application. I use OpenBSD, IPsec VPNs and run the access points wide
open.

>
> Perhaps what you are saying is that if one is connected to a "hostile"
> LAN like a coffee shop, then wireless security does not protect one
> from threats within that LAN? And in such cases, VPN to a non-
> hostile (if you have one) LAN is best?
>
> That makes sense. Sort of like saying that a deadbolt will not
> protect you from strangers already in your house. But that's not to
> say that there's no reason to lock your doors ! Or that we shouldn't
> use a good deadbolt instead of an easily opened door latch. Or that
> administrators don't prefer to control who is allowed in the LAN.

Indeed, all of the above.

Regards,

Michael

seaweedsl
04-09-08, 12:47 PM
On Apr 8, 11:18 pm, msg <msg@_cybertheque.org_> wrote:

> I use OpenBSD, IPsec VPNs and run the access points wide
> open.
>
>
> Michael

Thanks for the clarifications, especially on your own approach.

I conclude that for our system as well as most homes and small
offices, G with WPA is still most efficient (vs B) and appropriate
path to wireless security.

Most of us just don't have time to go into alternative OSs etc, but
it's good to know what the serious techs are doing !

Cheers,
Steve

Jeff Liebermann
04-09-08, 01:28 PM
On Tue, 08 Apr 2008 23:18:31 -0500, msg <msg@_cybertheque.org_> wrote:

>Jeff says that OFDM is more robust, and perhaps the shorter
>packets at higher speeds suffer less from destructive multipath
>interference, but I have memory of analyses that show 802.11b to be
>generally more robust in open-air settings.

MatLab?

Shorter packet do have a higher probability of delivery in the
presense of fixed rate interference. That's also the reason for
packet fragmentation, which splits large packets into smaller pieces
so that the chances of getting clobbered by interfence is less. Of
course, with smaller packets, the packet overhead is increased,
resulting in a loss in thruput.
<http://www.wi-fiplanet.com/tutorials/article.php/1468331>

The problem with 802.11b modulation methods is that an interfering RF
blast at any inband frequency, during transmission, is fatal to the
entire packet. The data is trashed and needs to be resent. However,
802.11g OFDM consists of 52(?) carriers, each of which carry part of
the data. If one carrier gets trashed by interference or frequency
selective fading, the other carriers will still make it through and
get decoded.

>He also says that
>slower OFDM speeds compared against equivalent DSSS speeds provide
>superior channel capacity; I have no experience to evaluate this.

It's not a huge difference. With 802.11b, all management packets are
sent at 1Mbit/sec. That takes more airtime than the same 802.11g
management packets sent at 6Mbits/sec.

A very rough indication is the difference in thruput between
11Mbits/sec 802.11b versus 12Mbits/sec 802.11g. You'll be lucky to
get more than 4.5Mbits/sec thruput with 11Mbits/sec, but can easily
obtain 6Mbits/sec at 12Mbits/sec. OFDM (with 802.11b compatibility
off) has very close to 50% of raw data rate thruput. CCK is perhaps
about 40%. Not a huge difference, but noticeable.

Also see:
<http://pdos.csail.mit.edu/roofnet/doku.php?id=interesting>
These are some observations on the performance of the MIT Roofnet mesh
network in real conditions. Note that it's all 802.11b. Also note
the rather lousy "probability of delivery". I don't consider such
chronic and typical packet losses to be "robust". Similar networks
implimented using 802.11g work much better, with far less packet loss,
but over a smaller range/area.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558