Yet another architecture (sectorized multi-AP array). This is comparing apples
and oranges (except we don't know the variety of traditional apple Tolly is
comparing Xirrus to in the study).
I think the problem is all these vendors live in Silicon Valley flatland and
don't consider the effect of high density in three dimensions. The Novarum test
appeared to be an out-of-the-box comparison (no tweaks). I think it would be
relatively straightforward for a 3-story building to be surveyed and tested with
each vendors architecture and have an independent performance analysis conducted
after its been tuned to each vendors satisfaction. But who's going to pay for
it?
In the tests you see conducted by the industry trade magazines, one or several
of the vendors always decline to participate (not confidence-inspiring). Pay
attention to who doesn't.
Its an issue unique to wireless since it's the only medium that feeds upon
itself, and is context (implementer, building) dependent. What we need to know
are the assumed parameters for deployment of each vendor's architectures. If
the all defaults (all proprietary automated features) bet is off, then we
deserve to know exactly what each vendor is doing behind the scenes, especially
those that do not follow the spirit of the standards (SCA).
If they tell you it depends, then you need to know everything the product
does, and get recommendations for how to support all measure of services (voice,
video, data, location) and the hazards each have on the other.
-Original Message-
From: The EDUCAUSE Wireless Issues Constituent Group Listserv
[mailto:[EMAIL PROTECTED] On Behalf Of Chad Frisby
Sent: Monday, March 31, 2008 4:41 PM
To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU
Subject: Re: [WIRELESS-LAN] Aruba's SCA vs. MCA whitepaper [was: Open Wireless
in Higher Ed]
Wireless Density of users and co-channel interference has already been
solved. Micro cell or channel blanket architectures do not.
Independent 3rd party test-results below by Tolly Group.
http://www.tolly.com/DocDetail.aspx?DocNumber=206152
http://www.tolly.com/DocDetail.aspx?DocNumber=207181
Chad Frisby
303.406.3222
-Original Message-
From: The EDUCAUSE Wireless Issues Constituent Group Listserv
[mailto:[EMAIL PROTECTED] On Behalf Of Charles
Spurgeon
Sent: Monday, March 31, 2008 2:31 PM
To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU
Subject: Re: [WIRELESS-LAN] Aruba's SCA vs. MCA whitepaper [was: Open
Wireless in Higher Ed]
On Wed, Mar 26, 2008 at 10:31:50PM -0500, Frank Bulk - iNAME wrote:
I wish it was easier to evaluate the performance (not only aggregrate
throughput, but also QoS) of the MCA and SCA products in various
scenarios
and density and usage, but unfortunately examining the impact of
co-channel
interference on a large scale in variety of building types and
architectures
with lots of APs and clients with realistic traffic patterns (in terms
of
type and longitudinally over time) is not currently possible with the
tools
available. I think we would learn that there certain scenarios where
one
performs generally better over another.
I, for one, would like to see more vendors step up and do the kind of
testing of co-channel interference issues that was described in the
recent Novarum whitepaper:
http://www.novarum.com/documents/WLANScaleTesting.pdf
As a user of typical multi-channel equipment, I'm not focussed on the
SCA versus MCA debate. Instead, I would very much like to see more
real-world test results on how the typical multiple APs on multiple
channels (MCA) approach works at scale and under traffic loads.
I think it's very interesting that the author of the Novarum
whitepaper is also one of the developers of the 802.11 MAC, and that
he states that he was surprised at how easily we could drive these
systems to unstable behavior.
I've heard complaints from the vendors whose gear was used in the
Novarum test. But I haven't seen any third-party tests commissioned by
those vendors to replicate the tests and show where the problems were
in the Novarum tests.
I would be much more impressed by actual third-party test results
based on a significant scale layout like the one used in the Novarum
tests, rather than hearing complaints about the how the test was
unfair since it was done under the auspices of Meru.
The problems of co-channel interference and wireless channel meltdown
under load are too important to be left to the marketing departments
of the wireless vendors. On our campus the community has been adopting
wireless networking at extremely high rates, and this technology has
become much too important to allow it to be supported this poorly.
Isn't it long past time for more real-world scale testing like the
Novarum tests to be done to investigate the issues with CCI and
channel meltdown under load in 802.11b/g systems and to develop some
approaches for identifying and dealing with those issues?
-Charles
Charles E. Spurgeon / UTnet
UT Austin ITS / Networking
[EMAIL
