Re: How many SSIDs can be listed?
On Wed, 2008-03-12 at 11:59 -0400, Robert Moskowitz wrote: > > Matthew Saltzman wrote: > > On Tue, 2008-03-11 at 10:55 -0400, Robert Moskowitz wrote: > > > >> Dan Williams wrote: > >> > >>> Are any of the APs hidden? > >>> > >>> > >> If they are 'hidden' (which is a myth, read my paper on this), they are > >> not of interest. Hidding an SSID is a waste of effort. And it > >> seriously breaks AP roaming. > >> > > > > But we're talking about the client side here. There are, unfortunately, > > still admins that insist (contrary to all advice) on hiding their SSIDs. > > I may (do!) need to connect to one of these nets, and I have no > > influence over their policy 8^(. > > > And thus you have to hand-craft your connect information. Your client > has to do an active scan to find the APs for this SSID, doing it when > you need it, not when it can check other channels in passive scanning > during 'free time'. So I have to "connect to other wireless network" to get to it. That's not really a problem (as long as it actually works...which it has been, recently). > > Sigh. 802.11 scanning is really dorky. > > OH, hopefully you only have ONE hidden SSID definition active. If you > have more, then EACH is a separate active scan operation. And on the A > band, boy does this HURT! Fortunately, that's the case (and I'm not using A band, either). -- Matthew Saltzman Clemson University Mathematical Sciences mjs AT clemson DOT edu http://www.math.clemson.edu/~mjs ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
Matthew Saltzman wrote: > On Tue, 2008-03-11 at 10:55 -0400, Robert Moskowitz wrote: > >> Dan Williams wrote: >> >>> Are any of the APs hidden? >>> >>> >> If they are 'hidden' (which is a myth, read my paper on this), they are >> not of interest. Hidding an SSID is a waste of effort. And it >> seriously breaks AP roaming. >> > > But we're talking about the client side here. There are, unfortunately, > still admins that insist (contrary to all advice) on hiding their SSIDs. > I may (do!) need to connect to one of these nets, and I have no > influence over their policy 8^(. > And thus you have to hand-craft your connect information. Your client has to do an active scan to find the APs for this SSID, doing it when you need it, not when it can check other channels in passive scanning during 'free time'. Sigh. 802.11 scanning is really dorky. OH, hopefully you only have ONE hidden SSID definition active. If you have more, then EACH is a separate active scan operation. And on the A band, boy does this HURT! ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
On Tue, 2008-03-11 at 10:55 -0400, Robert Moskowitz wrote: > > Dan Williams wrote: > > > > Are any of the APs hidden? > > > If they are 'hidden' (which is a myth, read my paper on this), they are > not of interest. Hidding an SSID is a waste of effort. And it > seriously breaks AP roaming. But we're talking about the client side here. There are, unfortunately, still admins that insist (contrary to all advice) on hiding their SSIDs. I may (do!) need to connect to one of these nets, and I have no influence over their policy 8^(. -- Matthew Saltzman Clemson University Mathematical Sciences mjs AT clemson DOT edu http://www.math.clemson.edu/~mjs ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
On Tue, 2008-03-11 at 13:09 -0400, Robert Moskowitz wrote: > Benoit Boissinot wrote: > > On Tue, Mar 11, 2008 at 2:08 PM, Dan Williams <[EMAIL PROTECTED]> wrote: > > > >> 0.6.x also combines APs with the same SSID in the UI. 0.7 splits them > >> out at the NetworkManager layer, while the applet combines APs that are > >> similar based on more than just SSID (SSID, security settings, band, > >> channel). > >> > > Does that mean that with 0.7, you can choose to connect to a 802.11a > > network instead of a b/g network (with the same SSID and security > > settings) ? > 'traditionally' you do that by limiting what channels you scan for the > AP for an SSID. > > Here at the IETF and next week at the IEEE 802 meeting, the practice is > to run different SSIDs for the different channel groups... > > How would the information be presented to the user in the UI? In 0.6.x, APs are grouped on SSID in both NM itself and the applet. In 0.7.x, NM exports will internally combine APs that have the same SSID, BSSID, security, and channel. The applet will futher combine (though only for display in the menu, not operationally) APs that share the same SSID, BSSID, security, and band. Dan ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
Benoit Boissinot wrote: > On Tue, Mar 11, 2008 at 2:08 PM, Dan Williams <[EMAIL PROTECTED]> wrote: > >> 0.6.x also combines APs with the same SSID in the UI. 0.7 splits them >> out at the NetworkManager layer, while the applet combines APs that are >> similar based on more than just SSID (SSID, security settings, band, >> channel). >> > Does that mean that with 0.7, you can choose to connect to a 802.11a > network instead of a b/g network (with the same SSID and security > settings) ? 'traditionally' you do that by limiting what channels you scan for the AP for an SSID. Here at the IETF and next week at the IEEE 802 meeting, the practice is to run different SSIDs for the different channel groups... How would the information be presented to the user in the UI? ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
On Tue, 2008-03-11 at 17:37 +0100, Benoit Boissinot wrote: > On Tue, Mar 11, 2008 at 2:08 PM, Dan Williams <[EMAIL PROTECTED]> wrote: > > 0.6.x also combines APs with the same SSID in the UI. 0.7 splits them > > out at the NetworkManager layer, while the applet combines APs that are > > similar based on more than just SSID (SSID, security settings, band, > > channel). > > > > Does that mean that with 0.7, you can choose to connect to a 802.11a > network instead of a b/g network (with the same SSID and security > settings) ? You can from the UI, but wpa_supplicant doesn't support band-limiting yet, so underneath you're at the mercy of what specific BSSID wpa_supplicant decides it wants to connect to, whether that's on the 5GHz side or the 2.4GHz side. We need to teach the supplicant to accept a 'band' option for wireless networks, and to filter out APs that aren't on the specified band, then have NM pass that option to the supplicant. Dan ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
On Tue, Mar 11, 2008 at 2:08 PM, Dan Williams <[EMAIL PROTECTED]> wrote: > 0.6.x also combines APs with the same SSID in the UI. 0.7 splits them > out at the NetworkManager layer, while the applet combines APs that are > similar based on more than just SSID (SSID, security settings, band, > channel). > Does that mean that with 0.7, you can choose to connect to a 802.11a network instead of a b/g network (with the same SSID and security settings) ? regards, Benoit ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
Yo Derek! Fancy meeting you here. I will look you up later. Derek Atkins wrote: > There's another problem. The wireless extensions have a size limit > for the scan results data. The buffer size is a u16, which means you're > limited to 65535 bytes. The network manager buffer increase algorithm > keeps doubling the buffer size, so you get 2k, 4k, 8k, 16k, 32k, 64k.. > but 64k mod 2^16 == 0! Meaning you never actually get to try a full 64k > buffer. > > A workaround to this issue is to change the NM code to max out at > 65535 instead of 65536 or "10" (which is the current limit).. > > This is being a MAJOR problem to a bunch of us at the IETF because > we can easily hear well over 100 APs most of the time. Please! We are use to seeing some of the worst-case work environments with too many APs and SSIDs for most code to cope with. > Quoting Dan Williams <[EMAIL PROTECTED]>: > >> On Mon, 2008-03-10 at 23:40 -0400, Robert Moskowitz wrote: >>> Ver 0.6.4 in Centos 5.1 >>> >>> I am seeing 17 SSIDs in the current list. But I am not seeing one that >>> I expected to see. And some of the listed SSIDs are 'stale'; that is >>> they were visible in the part of the hotel I was in a couple minutes >>> ago, but not in this part. So I guess a second question is how do you >>> force a scan to produce a current SSID list? >> >> You don't force a scan. NetworkManager will periodically scan with a >> backoff algorithm; it will start at 20 seconds and back off to 2 >> minutes. APs are kept in the scan list for a maximum of 6 minutes >> before being culled. >> >> The problem is that wireless is hard, and sometimes cards/drivers miss >> beacons. Often they will not report all the APs that are known to be >> around at a given time. So NetworkManager takes a composite of the last >> few scans as the scan list. >> >> 0.6.x also combines APs with the same SSID in the UI. 0.7 splits them >> out at the NetworkManager layer, while the applet combines APs that are >> similar based on more than just SSID (SSID, security settings, band, >> channel). >> >>> Perhaps the question may be how many APs can be handled and then those >>> are turned into the SSID list (when more than one AP per SSID is found >>> as in the case of some of these SSIDs). >> >> Are any of the APs hidden? >> > ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
Dan Williams wrote: > On Mon, 2008-03-10 at 23:40 -0400, Robert Moskowitz wrote: > >> Ver 0.6.4 in Centos 5.1 >> >> I am seeing 17 SSIDs in the current list. But I am not seeing one that >> I expected to see. And some of the listed SSIDs are 'stale'; that is >> they were visible in the part of the hotel I was in a couple minutes >> ago, but not in this part. So I guess a second question is how do you >> force a scan to produce a current SSID list? >> > > You don't force a scan. NetworkManager will periodically scan with a > backoff algorithm; it will start at 20 seconds and back off to 2 > minutes. APs are kept in the scan list for a maximum of 6 minutes > before being culled. > This is a problem when you are moving around a lot. Well maybe not so much a problem if you are always wanting to connect to SSID ietf-a, regardless of which AP. But a problem if you are moving around in an area with a lot of open networks and you are looking for something to ride on... > The problem is that wireless is hard, Tell me about it. I work on the standards. Will be in Orlando next week for the 802 plenary meeting. > and sometimes cards/drivers miss beacons. Of course. Until we change 'everything' with 802.11s, scanning requires the radio to listen to each channel, one at a time, and hope to catch the BEACON for that channel. And not just a BEACON, but all the APs using a given channel. The standard does not allow for a radio to listen on all channels. 802.11n does change this a bit. 11s basically requires it (well for the mesh nodes at least). > Often they will not report all the APs that are known to be > around at a given time. Because they frequently have table limit sizes and can only record so many. > So NetworkManager takes a composite of the last few scans as the scan list. > Ouch. Not good for an actively moving device. A person walking can easily encounter a few APs for a given SSID on the same channel. Which one is really current? So when you do an ASSOCIATE on a given channel, which AP do you put in as the destination BSSID? > 0.6.x also combines APs with the same SSID in the UI. As it should. People don't understand lots of APs in an SSID unless they install them! > 0.7 splits them out at the NetworkManager layer, AH, so NetworkManager controls the ASSOCIATE, not the device driver? > while the applet combines APs that are > similar based on more than just SSID (SSID, security settings, band, > channel). > Channel/band? well other than b/g vs a vs n. And within an SSID you cannot have different security settings, per the spec. >> Perhaps the question may be how many APs can be handled and then those >> are turned into the SSID list (when more than one AP per SSID is found >> as in the case of some of these SSIDs). >> > > Are any of the APs hidden? > If they are 'hidden' (which is a myth, read my paper on this), they are not of interest. Hidding an SSID is a waste of effort. And it seriously breaks AP roaming. ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
There's another problem. The wireless extensions have a size limit for the scan results data. The buffer size is a u16, which means you're limited to 65535 bytes. The network manager buffer increase algorithm keeps doubling the buffer size, so you get 2k, 4k, 8k, 16k, 32k, 64k.. but 64k mod 2^16 == 0! Meaning you never actually get to try a full 64k buffer. A workaround to this issue is to change the NM code to max out at 65535 instead of 65536 or "10" (which is the current limit).. This is being a MAJOR problem to a bunch of us at the IETF because we can easily hear well over 100 APs most of the time. -derek Quoting Dan Williams <[EMAIL PROTECTED]>: > On Mon, 2008-03-10 at 23:40 -0400, Robert Moskowitz wrote: >> Ver 0.6.4 in Centos 5.1 >> >> I am seeing 17 SSIDs in the current list. But I am not seeing one that >> I expected to see. And some of the listed SSIDs are 'stale'; that is >> they were visible in the part of the hotel I was in a couple minutes >> ago, but not in this part. So I guess a second question is how do you >> force a scan to produce a current SSID list? > > You don't force a scan. NetworkManager will periodically scan with a > backoff algorithm; it will start at 20 seconds and back off to 2 > minutes. APs are kept in the scan list for a maximum of 6 minutes > before being culled. > > The problem is that wireless is hard, and sometimes cards/drivers miss > beacons. Often they will not report all the APs that are known to be > around at a given time. So NetworkManager takes a composite of the last > few scans as the scan list. > > 0.6.x also combines APs with the same SSID in the UI. 0.7 splits them > out at the NetworkManager layer, while the applet combines APs that are > similar based on more than just SSID (SSID, security settings, band, > channel). > >> Perhaps the question may be how many APs can be handled and then those >> are turned into the SSID list (when more than one AP per SSID is found >> as in the case of some of these SSIDs). > > Are any of the APs hidden? > > Dan > > ___ > NetworkManager-list mailing list > NetworkManager-list@gnome.org > http://mail.gnome.org/mailman/listinfo/networkmanager-list > -- Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory Member, MIT Student Information Processing Board (SIPB) URL: http://web.mit.edu/warlord/PP-ASEL-IA N1NWH [EMAIL PROTECTED]PGP key available ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: How many SSIDs can be listed?
On Mon, 2008-03-10 at 23:40 -0400, Robert Moskowitz wrote: > Ver 0.6.4 in Centos 5.1 > > I am seeing 17 SSIDs in the current list. But I am not seeing one that > I expected to see. And some of the listed SSIDs are 'stale'; that is > they were visible in the part of the hotel I was in a couple minutes > ago, but not in this part. So I guess a second question is how do you > force a scan to produce a current SSID list? You don't force a scan. NetworkManager will periodically scan with a backoff algorithm; it will start at 20 seconds and back off to 2 minutes. APs are kept in the scan list for a maximum of 6 minutes before being culled. The problem is that wireless is hard, and sometimes cards/drivers miss beacons. Often they will not report all the APs that are known to be around at a given time. So NetworkManager takes a composite of the last few scans as the scan list. 0.6.x also combines APs with the same SSID in the UI. 0.7 splits them out at the NetworkManager layer, while the applet combines APs that are similar based on more than just SSID (SSID, security settings, band, channel). > Perhaps the question may be how many APs can be handled and then those > are turned into the SSID list (when more than one AP per SSID is found > as in the case of some of these SSIDs). Are any of the APs hidden? Dan ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
How many SSIDs can be listed?
Ver 0.6.4 in Centos 5.1 I am seeing 17 SSIDs in the current list. But I am not seeing one that I expected to see. And some of the listed SSIDs are 'stale'; that is they were visible in the part of the hotel I was in a couple minutes ago, but not in this part. So I guess a second question is how do you force a scan to produce a current SSID list? Perhaps the question may be how many APs can be handled and then those are turned into the SSID list (when more than one AP per SSID is found as in the case of some of these SSIDs). ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
