802.11b/802.11g What sees what?
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Thread: 802.11b/802.11g What sees what?

  1. #1
    King Tutorial-ankhamun
    Join Date
    Jul 2004
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    897

    802.11b/802.11g What sees what?

    Ok, I know Iíve asked this before on a forum someplace, but Iím still trying to figure out the right answers. What does a 802.11b sniffer on a 802.11g network see, and vice versa using both Promiscuous mode and Monitor mode? For those that donít understand the difference between the two modes read:

    Promiscuous mode http://en.wikipedia.org/wiki/Promiscuous_mode
    Monitor mode http://en.wikipedia.org/wiki/Monitor_mode

    Seems a lot of folks get them confused. To further complicate the matter, some cards seem not to support these modes (for example, ipw2200 supports Monitor with the newest drivers in Linux but does not seem to support Promiscuous in Windows or Linux for what I have tried so far, at least in the distribution Iím using). Here are my questions, but in a more concise manner:

    1. 802.11b sniffer on a 802.11g network see when in Monitor mode?
    2. 802.11b sniffer on a 802.11g network see when in Promiscuous mode?
    3. 802.11g sniffer on a 802.11b network see when in Monitor mode?
    4. 802.11g sniffer on a 802.11b network see when in Promiscuous mode?

    I plan to do some systematic tests soon and post results, but my hardware is limited and as I stated before, lack of support with some chipsets does complicate maters. As best as I can tell so far these may be the answers:

    1. Just 802.11 management traffic (beacons and such) and broadcast traffic.
    2. Just broadcast traffic.
    3. Everything.
    4. Everything but 802.11 management traffic (beacons and such).

    Also, if anyone can recommend a good 802.11G card that will support Promiscuous in Windows and Monitor in Linux I would appreciate it. Iíve found sites that recommend good cards, but sometime the revision numbers can cause confusion as to what modes are supported.

  2. #2
    King Tutorial-ankhamun
    Join Date
    Jul 2004
    Posts
    897

    802.11b/802.11g What sees what?

    Ok, I know Iíve asked this before on a forum someplace, but Iím still trying to figure out the right answers. What does a 802.11b sniffer on a 802.11g network see, and vice versa using both Promiscuous mode and Monitor mode? For those that donít understand the difference between the two modes read:

    Promiscuous mode http://en.wikipedia.org/wiki/Promiscuous_mode
    Monitor mode http://en.wikipedia.org/wiki/Monitor_mode

    Seems a lot of folks get them confused. To further complicate the matter, some cards seem not to support these modes (for example, ipw2200 supports Monitor with the newest drivers in Linux but does not seem to support Promiscuous in Windows or Linux for what I have tried so far, at least in the distribution Iím using). Here are my questions, but in a more concise manner:

    1. 802.11b sniffer on a 802.11g network see when in Monitor mode?
    2. 802.11b sniffer on a 802.11g network see when in Promiscuous mode?
    3. 802.11g sniffer on a 802.11b network see when in Monitor mode?
    4. 802.11g sniffer on a 802.11b network see when in Promiscuous mode?

    I plan to do some systematic tests soon and post results, but my hardware is limited and as I stated before, lack of support with some chipsets does complicate maters. As best as I can tell so far these may be the answers:

    1. Just 802.11 management traffic (beacons and such) and broadcast traffic.
    2. Just broadcast traffic.
    3. Everything.
    4. Everything but 802.11 management traffic (beacons and such).

    Also, if anyone can recommend a good 802.11G card that will support Promiscuous in Windows and Monitor in Linux I would appreciate it. Iíve found sites that recommend good cards, but sometime the revision numbers can cause confusion as to what modes are supported.

  3. #3
    Banned
    Join Date
    Jul 2004
    Posts
    297
    ok how about this one that has a prism54 chip, of course im guessing its for a laptop, and as always when buying a wifi card for use with linux triple check the revisions before you purchase it.
    http://secure.newegg.com/app/Custrat...tem=33-150-004

  4. #4
    Banned
    Join Date
    Jul 2004
    Posts
    297
    ok how about this one that has a prism54 chip, of course im guessing its for a laptop, and as always when buying a wifi card for use with linux triple check the revisions before you purchase it.
    http://secure.newegg.com/app/Custrat...tem=33-150-004

  5. #5
    Senior Member
    Join Date
    Oct 2001
    Posts
    748
    Irongeek- I think it depends on how the endpoint is configured. For instance, if you have you 802.11g setup to only broadcast in 802.11g I don't think the 802.11B network card would pick up any traffic. Mainly because the 802.11b card cannot pick up the modulation from the 802.11g end point. 802.11b can't recognize ODFM modulation. Only DSSS and CKK modulation can be received.

    So if your 802.11g endpoint and card had to handshake their way down into the sub 11Mb/sec speed range then I guess it could be possible to pickup a signal as even 802.11g uses the same modulation as 802.11b when the speed is 1,2, 5, or 11 Mb/sec where DSSS, and CCK is used for signaling.

    Even then I have to wonder because 802.11g uses what the standard calls ERP-OFDM, ERP-PBCC, DSSS-OFDM, ERP-DSSS/CCK. So the standard DSSS and CCK has been extended beyond what 802.11b had. 802.11g is called extended rate signaling, 802.11b has high rate signaling.

    It is described in clause 18 and 19 of the official IEEE 802.11g standard.

  6. #6
    Senior Member
    Join Date
    Oct 2001
    Posts
    748
    Irongeek- I think it depends on how the endpoint is configured. For instance, if you have you 802.11g setup to only broadcast in 802.11g I don't think the 802.11B network card would pick up any traffic. Mainly because the 802.11b card cannot pick up the modulation from the 802.11g end point. 802.11b can't recognize ODFM modulation. Only DSSS and CKK modulation can be received.

    So if your 802.11g endpoint and card had to handshake their way down into the sub 11Mb/sec speed range then I guess it could be possible to pickup a signal as even 802.11g uses the same modulation as 802.11b when the speed is 1,2, 5, or 11 Mb/sec where DSSS, and CCK is used for signaling.

    Even then I have to wonder because 802.11g uses what the standard calls ERP-OFDM, ERP-PBCC, DSSS-OFDM, ERP-DSSS/CCK. So the standard DSSS and CCK has been extended beyond what 802.11b had. 802.11g is called extended rate signaling, 802.11b has high rate signaling.

    It is described in clause 18 and 19 of the official IEEE 802.11g standard.

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