Subject: ad-hoc terminals are found at #503

From: Katsushi Kobayashi <[email-masked]>
Date: Wed, 17 Jul 2002 10:46:02 +0900

I have investigated wireless stations in room 503 at 10:30JST.
The stations found at this time except for AP provided by network
services. Please stop them.

IETF                              	02:9C:CB:E1:C0:81	10	39	Ad-hoc
tsunami                           	7A:03:88:01:B7:03	6	32	Ad-hoc

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From: [email-masked]
Date: Thu, 18 Jul 2002 12:04:22 +0000

A couple of general questions about 802.11 at IETF in Japan

1)	is there some aspect of the telecommunications/regulations here
	in Japan restricting the number of channels for RF use which affected
	the problem? Did it help or hinder? -This is a 'cannot fix' problem
	for IETF, but would be interesting to know, and to try and feed back
	into national regulatory process for RF management. After all, the
	density of endpoints and stations is probably close to a future world
	dream. 

2)	is there some aspect of the density of wireless stations, station names
	and SSID behaviour which contributed to the problem? I am hearing 
	gossip which suggests in some cases in RF space 'more is better' is
	a false model, and that 3 stations in rooms where 4 are, might be
	cleaner.

	A consideration here is that people choose to sit close to the
	middle of the room, and some rooms the aerials are in the corners
	so the area of maximum overlap of signal is ... the weighted centroid
	of the middle of the room! Or the ven diagram overlap or whatever.

	Maybe more 'randomy' placement of the stations, or all along one wall
	would be better? I don't know. Could that kind of thing be tested
	passively with an RF meter rather than with the massed laptops of IETF?
	(and the hosting BCP updated...)

And, the tricky third question

	....or is this just yet another complexity which cannot be solved
	by single-point changes...

cheers and thanks to the NOC who are clearly working very very hard to deliver
the best 802.11 they can, in trying circumstances (Typhoons do not help with
external aerials, rogue SSID ad-hoc, and who knows what else)

-George

--
George Michaelson       |  APNIC
Email: [email-masked]    |  PO Box 2131 Milton QLD 4064
Phone: +61 7 3858 3100  |  Australia
  Fax: +61 7 3858 3199  |  http://www.apnic.net

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From: Joel Jaeggli <[email-masked]>
Date: Wed, 17 Jul 2002 19:34:47 -0700 (PDT)

> 	density of endpoints and stations is probably close to a future world

actually japan has four non-overlapping channels 802.11 channel 1 6 11 14 
whereas the US has only three because their 2.4ghz ism band goes from 
2.4-2.5 and ours goes from 2.4-2.483. some commonwealth countries have 
more stringent output regulations than the US or JP but that's not an 
issue here.
 
> 	a false model, and that 3 stations in rooms where 4 are, might be

you need to do some engineering in order to make is such that the ap's 
sitting on the same channels can't hear to much of each other. noise is 
the biggest killer here because it results in more retransmissions which 
results in deeper buffers on the ap's which results in more 
retramismission which results in the ap's crashing from buffer-overflows 
and overall results in reduced performance...

the accompaning issues is more than 60-100 clients per ap (and ~200=death)
really results in reduced performance as well, particulallry if most of
them are active so more ap's can result in better localized performance,
assuming you get a handle on the rf issue.

rogue ap and adhoc nodes result in their own set of confusion assuming you 
client works right the biggest effect should be more noise, if your client 
doesn't work properly (the apple one apparently) then other bad things may 
happen.

> 	(and the hosting BCP updated...)

yeah it can be tested but the rf environement looks way wierder with 1200
addional transmitters and 50 tons of rf absorbing meat in the space then
it does without them so unless you have a very cool testbed environment
you don't really know what your changes will do unless you try them

-- 
-------------------------------------------------------------------------- 
Joel Jaeggli	      Academic User Services   [email-masked]    
--    PGP Key Fingerprint: 1DE9 8FCA 51FB 4195 B42A 9C32 A30D 121E      --
  In Dr. Johnson's famous dictionary patriotism is defined as the last
  resort of the scoundrel.  With all due respect to an enlightened but
  inferior lexicographer I beg to submit that it is the first.
	   	            -- Ambrose Bierce, "The Devil's Dictionary"

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From: Carsten Bormann <[email-masked]>
Date: Thu, 18 Jul 2002 04:35:28 +0200

Japan can use all 14 WiFi channels (World/ETSI can use 13, US/FCC 11).
The IETF network was restricted to the US 11 channels, obviously so that users 
of US cards would not be left cold.

On Monday, and for some time on Wednesday, there were problems with overlapping 
channels.  In WiFi, channel bandwidth is between 20 and 25 MHz, so there must be 
a 4 to preferably 5 channel (5 MHz) gap between the channels that are actually 
being used.  Stations on the same channel coordinate.  Stations on different but 
overlapping channels essentially serve as efficient jammers to each other.

While this problem was solved by Monday dinner time using an appropriate 
frequency plan (using only channels 1, 6, 11), the rogue stations that 
repeatedly popped up at channels 3 and 10 probably did not help.

A lot of the problems that are seen in real wireless networks connected by 
random Ethernet switches is that some Ethernet switches do not update their MAC 
address tables fast enough to cope with fast roaming.  I'd assume (but don't 
know for sure) that we had our share of that.

I've been busy this week, so I have not attempted a full analysis of what 
happened, but these are some data points.
I believe that IETF meetings are consistently the largest groups of WLAN users 
in one network that ever happen, so they would make great research subjects (for 
non-intrusive research, please).

Gruesse, Carsten

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From: [email-masked]
Date: Thu, 18 Jul 2002 11:38:52 +0900

>assuming you get a handle on the rf issue.

	maybe at IETF55, should we invite 802.11b experts to measure behaviors,
	expreiment with basestation placement, and such?

itojun

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From: Atsushi Onoe <[email-masked]>
Date: Thu, 18 Jul 2002 11:40:15 +0900 (JST)

> A couple of general questions about 802.11 at IETF in Japan

I think problems are not specific in Japan but may be specific in IETF.

There are only 3 non-overlapping channel (e.g. 1-6-11) in 802.11b.
Actually there is another channel (14) which almost non-overlapping
to channel 11.  We enabled the channel for plenary.

Most of the problems are due to the density of station.  Sometimes
there are 300+ terminals in one room.  Once an access point reboot
due to overload, the access point should expecte 100+ simultenous
association request after boot up.  If the access point cannot handle
such request and reboot again, that is the problem.

We have also tried micro-cell to reduce stations associating single
access point, but it is worse because of flooding of hand-over.

We should expect AP vender to update their software to handle
IETF meeting and other such congested wireless terminal environment,
if any...

Atsushi Onoe, NOC

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From: Atsushi Onoe <[email-masked]>
Date: Thu, 18 Jul 2002 12:10:55 +0900 (JST)

> channels.

Sometimes we intentionally use overlapping channel configuration.
Basically, overlapping channel reduced performance, but the connectivity
should still remain.  But the number of connected stations per access
points affects stability of access point, which is too bad.

Atsushi Onoe

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From: [email-masked]
Date: Thu, 18 Jul 2002 14:57:57 +0000

> more stringent output regulations than the US or JP but that's not an 

Thanks for the correction. I don't know where I got the idea it was a lower
number of channels. Maybe some other country.

> assuming you get a handle on the rf issue.

Maybe events like IETF need some hypothetical micro-cell below even the
normal small cell size, so you can seed enough stations in the room to
meet demand. 

> doesn't work properly (the apple one apparently) then other bad things may 

I think we just did Apple a huge favour showing them some serious scaling
problems with their current implementation. Better its found out here than
in the real world!

> you don't really know what your changes will do unless you try them.
> 
> 

Not to get too vendor centric the Cisco tools really helped us map hotspots
at work, but I'm not sure it would work as well here. 

Maybe some kind of instrumented (netramet? flows??? :-) drivers could turn us
all into a version of the Jun IPv6 windscreen wiper trick on taxi's, but as a
health meter on the network. Summarized status could be sent in Multicast for a
collection agent.

-George

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From: [email-masked]
Date: Thu, 18 Jul 2002 14:58:39 +0000

> 	expreiment with basestation placement, and such?

I very much agree. I think we can eat our own dogfood here!

-George

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From: Daniel Senie <[email-masked]>
Date: Thu, 18 Jul 2002 01:23:03 -0400

>I very much agree. I think we can eat our own dogfood here!

At the Minneapolis meeting, the wireless network worked quite well. Agere / 
Orinoco provided the equipment and engineers who knew how to properly set 
it up. I saw few if any problems in Minneapolis. Having spent the time to 
become a certified reseller, there are lots of things that can affect 
sites, and ways to deal with large meetings. I do not know if the Yokohama 
network was engineered properly or not. I did see some email at the start 
of the week which indicated the channels were not well chosen, though it 
appears that has been remedied.

It might make sense to just spend the money to properly design these 
networks, even if they're for short duration use.

-----------------------------------------------------------------
Daniel Senie                                        [email-masked]
Amaranth Networks Inc.                    http://www.amaranth.com

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From: John Stracke <[email-masked]>
Date: Thu, 18 Jul 2002 09:31:15 -0400

>IETF meeting and other such congested wireless terminal environment,
I suppose it's possible that there are no other environments as 
congested as the IETF...but the 802.11x vendors need to hope that there 
will be.  It might be possible to get them to treat the IETF as an 
opportunity to stress-test their access points.  For Atlanta, the host 
is Nokia, which sells an access point 
(<http://www.nokia.com/corporate/wlan/point_a032.html>); maybe the 
organizers could talk to their engineers and get debugging models. 
 Better to do it with the IETF, which is capable of understanding why 
debugging is hard, than with a flash crowd at Starbucks.  :-)

-- 
/========================================================\
|John Stracke                    |Principal Engineer     |
[email-masked]   |Incentive Systems, Inc.|
|http://www.incentivesystems.com |My opinions are my own.|
|========================================================|
|This is the .sig that says... Ni!                       |
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