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Thread: 3com WAP - public/secure and 'N' vs B/G

  1. #1
    ps56k
    Guest

    3com WAP - public/secure and 'N' vs B/G

    I was at our local library today,
    and it appears they have several WAP's installed,
    but I had problems getting connected...

    There are two SSID's -
    one is public and one is private/secure.

    Using WiFi Hopper it displayed a couple of 3Com access points
    with what appeared to be "related" MAC addresses...
    00:22:57:00:13:40 - public
    00:22:57:00:13:42 - secure

    Anyway - when I got home & sent an email to their "tech" person
    and mentioned that I was having a problem,
    here was the jist of the reply...
    Wrong tech language makes me not hopeful :)

    Since I don't have anything running B/G/N -
    could they have something configured to support N,
    that accidently doesn't allow B/G to connect - and they don't know it :)

    ----

    I have familiarity with our
    wireless access points, and also have familiarity with wireless
    setups. I'm sorry you had some connection problems when you were at
    the library. Every so often, our wireless connection weakens, but
    overall, the signal is usually pretty strong. However, I have a few
    ideas that you might want to try:

    If you were sitting at a table near the magazines, you would be near
    one of the wireless hubs, which should have boosted the
    signal. There are 4 hubs throughout the library (2 downstairs, one
    in the meeting room and one in Youth Services upstairs) and are for
    anyone to use. You indicated that your laptop showed access points
    of LLD-Public and LLD and if you select one of these, your laptop
    should make the connection with no problem.

    The LLD-Public connection is using the newest technology for 802.11 N.

    In addition, some of the newer laptops, like ones from Dell, need a
    utility enabled to allow complete connection. We ran into this
    problem with the new laptops for our computer classes, and I know
    another patron who also had this problem. If you are using a Dell,
    you might want to check that you have enabled the Dell wireless
    utility. You can go to the Dell website if you need to download it
    --- it is called Dell Wireless WLAN Card Utility. If you are using
    a laptop made by another manufacturer, there is most likely a similar
    utility for your wireless connections.

    Another thing to double-check are any firewall settings you might
    have enabled to protect your laptop when accessing wireless
    points. Our wireless network is unsecured (no password required).




  2. #2
    ps56k
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G


    "ps56k" <pschuman_no_spam_me@interserv.com> wrote in message
    news:AGHrl.11866$pr6.77@flpi149.ffdc.sbc.com...
    >I was at our local library today,
    > and it appears they have several WAP's installed,
    > but I had problems getting connected...
    >
    > There are two SSID's -
    > one is public and one is private/secure.
    >
    > Using WiFi Hopper it displayed a couple of 3Com access points
    > with what appeared to be "related" MAC addresses...
    > 00:22:57:00:13:40 - public
    > 00:22:57:00:13:42 - secure
    >
    > Anyway - when I got home & sent an email to their "tech" person
    > and mentioned that I was having a problem,
    > here was the jist of the reply...
    > Wrong tech language makes me not hopeful :)
    >
    > Since I don't have anything running B/G/N -
    > could they have something configured to support N,
    > that accidently doesn't allow B/G to connect - and they don't know it :)
    >
    > ----
    >
    > I have familiarity with our
    > wireless access points, and also have familiarity with wireless
    > setups. I'm sorry you had some connection problems when you were at
    > the library. Every so often, our wireless connection weakens, but
    > overall, the signal is usually pretty strong. However, I have a few
    > ideas that you might want to try:
    >
    > If you were sitting at a table near the magazines, you would be near
    > one of the wireless hubs, which should have boosted the
    > signal. There are 4 hubs throughout the library (2 downstairs, one
    > in the meeting room and one in Youth Services upstairs) and are for
    > anyone to use. You indicated that your laptop showed access points
    > of LLD-Public and LLD and if you select one of these, your laptop
    > should make the connection with no problem.
    >
    > The LLD-Public connection is using the newest technology for 802.11 N.
    >
    > In addition, some of the newer laptops, like ones from Dell, need a
    > utility enabled to allow complete connection. We ran into this
    > problem with the new laptops for our computer classes, and I know
    > another patron who also had this problem. If you are using a Dell,
    > you might want to check that you have enabled the Dell wireless
    > utility. You can go to the Dell website if you need to download it
    > --- it is called Dell Wireless WLAN Card Utility. If you are using
    > a laptop made by another manufacturer, there is most likely a similar
    > utility for your wireless connections.
    >
    > Another thing to double-check are any firewall settings you might
    > have enabled to protect your laptop when accessing wireless
    > points. Our wireless network is unsecured (no password required).
    >
    >

    here's some info I found -
    but it discusses the client side, not the AP side -
    ---
    802.11n APs that use the ISM band will indeed compete for air space with
    existing 802.11g APs. That's especially troublesome for 802.11n APs that use
    40 MHz channels, since the ISM band is only wide enough to fit 3
    non-overlapping 20 MHz channels (1, 6, and 11). For example, suppose an
    802.11n AP uses Channels 6 and 7 to create a 40 MHz channel -- that will
    generate co-channel interference for every other 802.11g AP in the vicinity
    except those using Channel 1.

    However, if you deploy old and new clients in the same frequency band,
    you'll need to enable coexistence mechanisms. Specifically, there are two
    modes of coexistence specified by 802.11n: legacy mode and mixed mode.

    In legacy mode, 802.11n clients behave just like 802.11g clients -- this
    amounts to using new hardware in the same old way as before, with little
    performance improvement. In mixed mode, 802.11n clients will send both the
    old-fashioned 802.11g preamble and the new 802.11n preamble before they
    start transmitting data.

    Mixed mode lets 802.11n clients take advantage of performance improvements
    like space-time block coding, short guard intervals, and frame aggregation,
    while giving 802.11g clients a "heads up" to avoid collisions. The extra
    preamble does add overhead, preventing 802.11n clients from achieving
    optimum throughput. But this is the price you must pay to ensure peaceful
    coexistence between old and new clients sharing the same band.





  3. #3
    LR
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G

    On 05/03/2009 03:23, ps56k wrote:
    > I was at our local library today,
    > and it appears they have several WAP's installed,
    > but I had problems getting connected...
    >
    > There are two SSID's -
    > one is public and one is private/secure.
    >
    > Using WiFi Hopper it displayed a couple of 3Com access points
    > with what appeared to be "related" MAC addresses...
    > 00:22:57:00:13:40 - public
    > 00:22:57:00:13:42 - secure
    >
    > Anyway - when I got home& sent an email to their "tech" person
    > and mentioned that I was having a problem,
    > here was the jist of the reply...
    > Wrong tech language makes me not hopeful :)
    >
    > Since I don't have anything running B/G/N -
    > could they have something configured to support N,
    > that accidently doesn't allow B/G to connect - and they don't know it :)


    If they are running an 802.11n network they don't have to allow 11b or
    11g to connect, the draft 11n only says that the equipment must be
    capable of connecting to legacy devices so the user can have the
    capability to run a mixed network.
    Look at the set of 11n mode options that are available on this emulator
    <http://support.dlink.com/Emulators/dir655/Basic_Wireless.html>

  4. #4
    ps56k
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G


    "LR" <lrme@privacy.net> wrote in message
    news:pZedndyweZrdCjLUnZ2dnUVZ8o-WnZ2d@bt.com...
    > On 05/03/2009 03:23, ps56k wrote:
    >> I was at our local library today,
    >> and it appears they have several WAP's installed,
    >> but I had problems getting connected...
    >>
    >> There are two SSID's -
    >> one is public and one is private/secure.
    >>
    >> Using WiFi Hopper it displayed a couple of 3Com access points
    >> with what appeared to be "related" MAC addresses...
    >> 00:22:57:00:13:40 - public
    >> 00:22:57:00:13:42 - secure
    >>
    >> Anyway - when I got home& sent an email to their "tech" person
    >> and mentioned that I was having a problem,
    >> here was the jist of the reply...
    >> Wrong tech language makes me not hopeful :)
    >>
    >> Since I don't have anything running B/G/N -
    >> could they have something configured to support N,
    >> that accidently doesn't allow B/G to connect - and they don't know it :)

    >
    > If they are running an 802.11n network they don't have to allow 11b or 11g
    > to connect, the draft 11n only says that the equipment must be capable of
    > connecting to legacy devices so the user can have the capability to run a
    > mixed network.
    > Look at the set of 11n mode options that are available on this emulator
    > <http://support.dlink.com/Emulators/dir655/Basic_Wireless.html>


    If the access point is setup for 802.11n - and only 802.11n -
    would I still see the SSID beacon on my b/g card via NetStumbler, Hopper,
    Windows ?

    Is the beacon packet seen by all technologies at the lowest common "speed &
    structure",
    and only goes into 802.11n mode after the actual connection ?

    Would I see the SSID, but just not be able to establish a connection ?



  5. #5
    LR
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G

    On 05/03/2009 15:33, ps56k wrote:
    > "LR"<lrme@privacy.net> wrote in message
    > news:pZedndyweZrdCjLUnZ2dnUVZ8o-WnZ2d@bt.com...
    >> On 05/03/2009 03:23, ps56k wrote:
    >>> I was at our local library today,
    >>> and it appears they have several WAP's installed,
    >>> but I had problems getting connected...
    >>>
    >>> There are two SSID's -
    >>> one is public and one is private/secure.
    >>>
    >>> Using WiFi Hopper it displayed a couple of 3Com access points
    >>> with what appeared to be "related" MAC addresses...
    >>> 00:22:57:00:13:40 - public
    >>> 00:22:57:00:13:42 - secure
    >>>
    >>> Anyway - when I got home& sent an email to their "tech" person
    >>> and mentioned that I was having a problem,
    >>> here was the jist of the reply...
    >>> Wrong tech language makes me not hopeful :)
    >>>
    >>> Since I don't have anything running B/G/N -
    >>> could they have something configured to support N,
    >>> that accidently doesn't allow B/G to connect - and they don't know it :)

    >> If they are running an 802.11n network they don't have to allow 11b or 11g
    >> to connect, the draft 11n only says that the equipment must be capable of
    >> connecting to legacy devices so the user can have the capability to run a
    >> mixed network.
    >> Look at the set of 11n mode options that are available on this emulator
    >> <http://support.dlink.com/Emulators/dir655/Basic_Wireless.html>

    >
    > If the access point is setup for 802.11n - and only 802.11n -
    > would I still see the SSID beacon on my b/g card via NetStumbler, Hopper,
    > Windows ?
    >
    > Is the beacon packet seen by all technologies at the lowest common "speed&
    > structure",
    > and only goes into 802.11n mode after the actual connection ?
    >
    > Would I see the SSID, but just not be able to establish a connection ?
    >
    >

    Without actually trying it I am not sure exactly what you would get.
    I have been doing a bit of reading about N recently and am not sure how
    some of these "legacy" connections are supposed to work.
    "During the definition of the 802.11g standard, it was realized that,
    since legacy 802.11b devices would not be able to decode the newer
    802.11g frames, there ought to be a separate mechanism to help legacy
    devices set their NAV correctly and therefore to reduce the percentage
    of collisions on air. The 11g standard made use of existing ‘protection
    mechanisms’ – RTS and CTS – to help legacy stations set their NAV.
    A similar situation arose during the definition of the 802.11n
    standard. Legacy 802.11a/b/g devices would not be able to decode the
    802.11n headers – and therefore a protection mechanism becomes
    necessary. One of these is the transmission of legacy preamble and
    header that enable the 802.11a/g/ device to detect the 802.11n packet
    and to decode the information in its signal field, from which the
    correct packet duration can be determined."
    <http://www.redpinesignals.com/Wireless-Handheld-Devices-The-802-11n-Advantage.pdf>

    My reading of that is you should see something.

    There was also this
    "Backward compatibility with legacy devices also may be enabled by
    forcing devices that are compliant with a newer version of the standard
    to transmit special frames using modes or data rates that are employed
    by legacy devices. For example, the newer devices may transmit Clear to
    Send/Ready to Send exchange frames or Clear to Send to self frames as
    may be employed in standard 11g. These special frames contain
    information that sets the network allocation vector of legacy devices
    such that these devices know when the wireless channel is in use by
    newer stations."
    <http://www.faqs.org/patents/app/20090028106>

    I have heard mixed reports about even using an 11n card with netstumbler
    with some people not getting it to work and one person who got it work
    only having it report speed at 54Mbs.



  6. #6
    Joe M
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G

    I recently borrowed a wireless router that accepts cell phone 3G wireless
    cards (this one was Sprint) and rebroadcasts the signal as standard b/g/n (I
    don't recall the router brand)... I wanted to see if this setup had enough
    bandwidth to allow three b/g equipped laptops to surf the net without
    obvious slowdowns (it did). The default was set to broadcast in b/g/n modes,
    so at one point I selected "n only" and after the router restarted all three
    laptops detected the network but could not connect. I then connected to the
    router with a network cable to change the setting back...




  7. #7
    Jeff Liebermann
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G

    On Thu, 5 Mar 2009 09:33:30 -0600, "ps56k"
    <pschuman_no_spam_me@interserv.com> wrote:

    >If the access point is setup for 802.11n - and only 802.11n -
    >would I still see the SSID beacon on my b/g card via NetStumbler, Hopper,
    >Windows ?


    Which N mode? Beam forming or spatial diversity? In beam forming
    (Ruckus Wireless), it's basically the same as 802.11g and you will see
    beacons. In spatial diversity (Airgo), I think (not sure) that the
    spec demands beacons. However, I'm fairly sure that the beacons are
    at 6Mbits/sec as in 802.11g. If you enable 802.11b compatibility,
    beam forming still works and it will belch beacons at 1Mbits/sec.
    However, with spatial diversity, 802.11b and MIMO speeds are mutually
    exclusive and I really doubt that you'll see 1Mbit/sec 802.11b
    beacons. No clue what happens with the new chips that do both beam
    forming and spatial diversity. I gotta read the specs to be sure, but
    I think that's the way it works.

    What you're basically asking is how does 802.11n operate in
    "greenfield" mode, where there are no constraints imposed by prior
    technology and legacy junk compatibility. Greenfield mode is very
    unlikely to be seen in a public library. My guess(tm) is what you're
    seeing is your wireless client software annoucing the highest level of
    acronym compliance. Just because you can't connect doesn't mean the
    lower standards are not available or functional. It would be nice if
    Netstumbler and others annouced all the various supported 802.11
    acronyms, but they don't.

    Incidentally, se have a somewhat similar derrangement at the local
    hospital. You can connect, but can't do anything without a WPA
    password *AND* and a VPN client. Everyone complains that they can't
    connect, until they finally read the splash page. Anyway, don't
    assume that it's 802.11n "only" just because you can't connect.

    >Is the beacon packet seen by all technologies at the lowest common "speed &
    >structure",
    >and only goes into 802.11n mode after the actual connection ?
    >
    >Would I see the SSID, but just not be able to establish a connection ?


    I don't know if this really helps, but the section on backwards
    compatibility:
    <http://en.wikipedia.org/wiki/IEEE_802.11n#Backward_compatibility>
    gives a few clues on how much of 802.11g technology (beacons) is
    compatible with 802.11n. I'm to busy/lazy right now to find a better
    reference.

    Gone to waste the whole weekend:
    <http://www.radiofest.org>



    --
    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

  8. #8
    LR
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G

    On 05/03/2009 16:45, LR wrote:
    > On 05/03/2009 15:33, ps56k wrote:
    >> "LR"<lrme@privacy.net> wrote in message
    >> news:pZedndyweZrdCjLUnZ2dnUVZ8o-WnZ2d@bt.com...
    >>> On 05/03/2009 03:23, ps56k wrote:
    >>>> I was at our local library today,
    >>>> and it appears they have several WAP's installed,
    >>>> but I had problems getting connected...
    >>>>
    >>>> There are two SSID's -
    >>>> one is public and one is private/secure.
    >>>>
    >>>> Using WiFi Hopper it displayed a couple of 3Com access points
    >>>> with what appeared to be "related" MAC addresses...
    >>>> 00:22:57:00:13:40 - public
    >>>> 00:22:57:00:13:42 - secure
    >>>>
    >>>> Anyway - when I got home& sent an email to their "tech" person
    >>>> and mentioned that I was having a problem,
    >>>> here was the jist of the reply...
    >>>> Wrong tech language makes me not hopeful :)
    >>>>
    >>>> Since I don't have anything running B/G/N -
    >>>> could they have something configured to support N,
    >>>> that accidently doesn't allow B/G to connect - and they don't know
    >>>> it :)
    >>> If they are running an 802.11n network they don't have to allow 11b
    >>> or 11g
    >>> to connect, the draft 11n only says that the equipment must be
    >>> capable of
    >>> connecting to legacy devices so the user can have the capability to
    >>> run a
    >>> mixed network.
    >>> Look at the set of 11n mode options that are available on this emulator
    >>> <http://support.dlink.com/Emulators/dir655/Basic_Wireless.html>

    >>
    >> If the access point is setup for 802.11n - and only 802.11n -
    >> would I still see the SSID beacon on my b/g card via NetStumbler, Hopper,
    >> Windows ?
    >>
    >> Is the beacon packet seen by all technologies at the lowest common
    >> "speed&
    >> structure",
    >> and only goes into 802.11n mode after the actual connection ?
    >>
    >> Would I see the SSID, but just not be able to establish a connection ?
    >>
    >>

    > Without actually trying it I am not sure exactly what you would get.
    > I have been doing a bit of reading about N recently and am not sure how
    > some of these "legacy" connections are supposed to work.
    > "During the definition of the 802.11g standard, it was realized that,
    > since legacy 802.11b devices would not be able to decode the newer
    > 802.11g frames, there ought to be a separate mechanism to help legacy
    > devices set their NAV correctly and therefore to reduce the percentage
    > of collisions on air. The 11g standard made use of existing ‘protection
    > mechanisms’ – RTS and CTS – to help legacy stations set their NAV.
    > A similar situation arose during the definition of the 802.11n standard.
    > Legacy 802.11a/b/g devices would not be able to decode the 802.11n
    > headers – and therefore a protection mechanism becomes necessary. One of
    > these is the transmission of legacy preamble and header that enable the
    > 802.11a/g/ device to detect the 802.11n packet and to decode the
    > information in its signal field, from which the correct packet duration
    > can be determined."
    > <http://www.redpinesignals.com/Wireless-Handheld-Devices-The-802-11n-Advantage.pdf>
    >
    >
    > My reading of that is you should see something.
    >
    > There was also this
    > "Backward compatibility with legacy devices also may be enabled by
    > forcing devices that are compliant with a newer version of the standard
    > to transmit special frames using modes or data rates that are employed
    > by legacy devices. For example, the newer devices may transmit Clear to
    > Send/Ready to Send exchange frames or Clear to Send to self frames as
    > may be employed in standard 11g. These special frames contain
    > information that sets the network allocation vector of legacy devices
    > such that these devices know when the wireless channel is in use by
    > newer stations."
    > <http://www.faqs.org/patents/app/20090028106>
    >
    > I have heard mixed reports about even using an 11n card with netstumbler
    > with some people not getting it to work and one person who got it work
    > only having it report speed at 54Mbs.
    >
    >

    Having got my XP laptop put back together and eventually finding someone
    who has an 11N only network I ran a few programs. I have used only b/g
    wireless cards.
    Kismet in Ubuntu reports an 802.11n network.
    XPSP2 laptop running the following:-
    1.WZC reports the SSID.
    2.Wifihopper reports SSID and an 11g network with the selected "40MHz"
    channel.
    The graph function works as well.
    3.Inssider reports SSID but the graph function doesn't work.
    4.Netstumbler was erratic to say the least. It wouldn't reliably report
    the SSID although it did report the correct MAC address. The graph would
    not work, you got a single line at the start and that was that.
    I later found that if the 11n "standard channel", assumption on my
    part, coincided with the channel that one of the nearby AP's was using
    then the graph stopped however if that AP was then switched off the
    graph would resume, it was pure luck that that AP was switched off.

    Vista SP1:-
    1.Vista "connect to a network" shows the SSID.
    2.Vistumbler 8.1 showed SSID and that it was an 11n network and the
    "40MHz" channel.
    3.Inssider showed SSID and the "40MHz" channel. The graph function
    worked in Vista.
    4.Xirrus WiFi Inspector showed SSID and that it was an 11n network. It
    also showed 2 channels,"wide" and "standard" I assume, which is why I
    went back and checked Netstumbler again and found the graph was now
    working and one of the AP's was no longer transmitting.
    5.None of the versions of wifihopper work correctly with the atheros b/g
    card in my Vista laptop. The latest version 1.2 build 2008-110600
    reports all networks as type 11a, so it works after a fashion but didn't
    try it as there may be other bugs.
    5.Inssider and Vistumbler are based on "netsh" commands so I didn't try
    that either.

    None showed speeds greater than 54Mbs.

    I have assumed that the 2 channels picked up by the Xirrus wifi
    inspector is correct and not a fault with the 11n AP or the Xirrus tool.
    The second channel I have assumed to be the "standard channel" and this
    does cause a problem for netstumbler if another AP is using it as well.
    I would be interested to know if anyone else has used this tool and
    noticed whether they have picked up 2 channels with an 11n network.

  9. #9
    ps56k
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G


    "LR" <lrme@privacy.net> wrote in message
    news:OdadnR9eZ_NUtCjUnZ2dnUVZ8q-WnZ2d@bt.com...
    > On 05/03/2009 16:45, LR wrote:
    >> On 05/03/2009 15:33, ps56k wrote:
    >>> "LR"<lrme@privacy.net> wrote in message
    >>> news:pZedndyweZrdCjLUnZ2dnUVZ8o-WnZ2d@bt.com...
    >>>> On 05/03/2009 03:23, ps56k wrote:
    >>>>> I was at our local library today,
    >>>>> and it appears they have several WAP's installed,
    >>>>> but I had problems getting connected...
    >>>>>
    >>>>> There are two SSID's -
    >>>>> one is public and one is private/secure.
    >>>>>
    >>>>> Using WiFi Hopper it displayed a couple of 3Com access points
    >>>>> with what appeared to be "related" MAC addresses...
    >>>>> 00:22:57:00:13:40 - public
    >>>>> 00:22:57:00:13:42 - secure
    >>>>>
    >>>>> Anyway - when I got home& sent an email to their "tech" person
    >>>>> and mentioned that I was having a problem,
    >>>>> here was the jist of the reply...
    >>>>> Wrong tech language makes me not hopeful :)
    >>>>>
    >>>>> Since I don't have anything running B/G/N -
    >>>>> could they have something configured to support N,
    >>>>> that accidently doesn't allow B/G to connect - and they don't know
    >>>>> it :)
    >>>> If they are running an 802.11n network they don't have to allow 11b
    >>>> or 11g
    >>>> to connect, the draft 11n only says that the equipment must be
    >>>> capable of
    >>>> connecting to legacy devices so the user can have the capability to
    >>>> run a
    >>>> mixed network.
    >>>> Look at the set of 11n mode options that are available on this emulator
    >>>> <http://support.dlink.com/Emulators/dir655/Basic_Wireless.html>
    >>>
    >>> If the access point is setup for 802.11n - and only 802.11n -
    >>> would I still see the SSID beacon on my b/g card via NetStumbler,
    >>> Hopper,
    >>> Windows ?
    >>>
    >>> Is the beacon packet seen by all technologies at the lowest common
    >>> "speed&
    >>> structure",
    >>> and only goes into 802.11n mode after the actual connection ?
    >>>
    >>> Would I see the SSID, but just not be able to establish a connection ?
    >>>
    >>>

    >> Without actually trying it I am not sure exactly what you would get.
    >> I have been doing a bit of reading about N recently and am not sure how
    >> some of these "legacy" connections are supposed to work.
    >> "During the definition of the 802.11g standard, it was realized that,
    >> since legacy 802.11b devices would not be able to decode the newer
    >> 802.11g frames, there ought to be a separate mechanism to help legacy
    >> devices set their NAV correctly and therefore to reduce the percentage
    >> of collisions on air. The 11g standard made use of existing ‘protection
    >> mechanisms’ – RTS and CTS – to help legacy stations set their NAV.
    >> A similar situation arose during the definition of the 802.11n standard.
    >> Legacy 802.11a/b/g devices would not be able to decode the 802.11n
    >> headers – and therefore a protection mechanism becomes necessary. One of
    >> these is the transmission of legacy preamble and header that enable the
    >> 802.11a/g/ device to detect the 802.11n packet and to decode the
    >> information in its signal field, from which the correct packet duration
    >> can be determined."
    >> <http://www.redpinesignals.com/Wireless-Handheld-Devices-The-802-11n-Advantage.pdf>
    >>
    >>
    >> My reading of that is you should see something.
    >>
    >> There was also this
    >> "Backward compatibility with legacy devices also may be enabled by
    >> forcing devices that are compliant with a newer version of the standard
    >> to transmit special frames using modes or data rates that are employed
    >> by legacy devices. For example, the newer devices may transmit Clear to
    >> Send/Ready to Send exchange frames or Clear to Send to self frames as
    >> may be employed in standard 11g. These special frames contain
    >> information that sets the network allocation vector of legacy devices
    >> such that these devices know when the wireless channel is in use by
    >> newer stations."
    >> <http://www.faqs.org/patents/app/20090028106>
    >>
    >> I have heard mixed reports about even using an 11n card with netstumbler
    >> with some people not getting it to work and one person who got it work
    >> only having it report speed at 54Mbs.
    >>
    >>

    > Having got my XP laptop put back together and eventually finding someone
    > who has an 11N only network I ran a few programs. I have used only b/g
    > wireless cards.
    > Kismet in Ubuntu reports an 802.11n network.
    > XPSP2 laptop running the following:-
    > 1.WZC reports the SSID.
    > 2.Wifihopper reports SSID and an 11g network with the selected "40MHz"
    > channel.
    > The graph function works as well.
    > 3.Inssider reports SSID but the graph function doesn't work.
    > 4.Netstumbler was erratic to say the least. It wouldn't reliably report
    > the SSID although it did report the correct MAC address. The graph would
    > not work, you got a single line at the start and that was that.
    > I later found that if the 11n "standard channel", assumption on my part,
    > coincided with the channel that one of the nearby AP's was using then the
    > graph stopped however if that AP was then switched off the graph would
    > resume, it was pure luck that that AP was switched off.
    >
    > Vista SP1:-
    > 1.Vista "connect to a network" shows the SSID.
    > 2.Vistumbler 8.1 showed SSID and that it was an 11n network and the
    > "40MHz" channel.
    > 3.Inssider showed SSID and the "40MHz" channel. The graph function worked
    > in Vista.
    > 4.Xirrus WiFi Inspector showed SSID and that it was an 11n network. It
    > also showed 2 channels,"wide" and "standard" I assume, which is why I went
    > back and checked Netstumbler again and found the graph was now working and
    > one of the AP's was no longer transmitting.
    > 5.None of the versions of wifihopper work correctly with the atheros b/g
    > card in my Vista laptop. The latest version 1.2 build 2008-110600 reports
    > all networks as type 11a, so it works after a fashion but didn't try it as
    > there may be other bugs.
    > 5.Inssider and Vistumbler are based on "netsh" commands so I didn't try
    > that either.
    >
    > None showed speeds greater than 54Mbs.
    >
    > I have assumed that the 2 channels picked up by the Xirrus wifi inspector
    > is correct and not a fault with the 11n AP or the Xirrus tool. The second
    > channel I have assumed to be the "standard channel" and this does cause a
    > problem for netstumbler if another AP is using it as well. I would be
    > interested to know if anyone else has used this tool and noticed whether
    > they have picked up 2 channels with an 11n network.


    since you could see the SSID -
    what happens when you try to connect to the 802.11n-only network ?

    and how did Hopper display the 802.11n with the 40mhz channel ?
    that would be my giveaway for a N-only network.




  10. #10
    LR
    Guest

    Re: 3com WAP - public/secure and 'N' vs B/G

    On 09/03/2009 16:32, ps56k wrote:

    > since you could see the SSID -
    > what happens when you try to connect to the 802.11n-only network ?


    It's not my network and it was encrypted so I couldn't connect. Joe M in
    his post reported that while he could see the network he could not
    connect when he tried. I know a person who works at the company and he
    assured me it was 11n only which is why I sat in the car park and ran a
    few tests.
    >
    > and how did Hopper display the 802.11n with the 40mhz channel ?
    > that would be my giveaway for a N-only network.


    You must have missed it.
    > XPSP2 laptop running the following:-


    >> 2.Wifihopper reports SSID and an 11g network with the selected "40MHz"
    >> channel.
    >> The graph function works as well.


    >
    >
    >



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