Date: Thu, 3 Sep 2009 14:59:59 -0400 From: Sin <sinister@gmail.com> To: "Sam Leffler" <sam@errno.com>, "Sin" <sinister@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: toggle short / long preamble with hostapd Message-ID: <F1A40CDCE4EC46F2820AC95ED03195C4@dts> References: <4790A7EF670C4698ADB76933788A218F@dts> <4A9E8C68.3060300@errno.com> <C3B4A04A39B74965AFA22B0A62876DB1@dts> <4AA0051F.8080202@errno.com>
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Sam, You understand correctly. I should of mentioned also before with high latency comes packet loss, around 15 %. Setting short preamble makes this 1 % or less. So you are right - this doesn't make sense. If I've read this correctly, short preamble is enabled. So I do the ping tests from each machine including the AP and latency is back to under 2ms. test# ifconfig ath0 list sta ADDR AID CHAN RATE RSSI IDLE TXSEQ RXSEQ CAPS FLAG 00:18:de:22:13:f1 1 10 36M 29.5 0 146 34480 EPS AE WPA 00:18:39:15:c6:24 2 10 48M 36.0 0 140 32160 EPS AE WPA I was using channel 1 before in the first email because it was free ( found it free with ifconfig ath0 up scan ) I'm wondering if just changing to channel 10 was the real fix. I wll take your advice and move everything to 8.0. Having the option in any version to force preamble mode would be a nice feature. ----- Original Message ----- From: "Sam Leffler" <sam@errno.com> To: "Sin" <sinister@gmail.com> Cc: <freebsd-net@freebsd.org> Sent: Thursday, September 03, 2009 2:04 PM Subject: Re: toggle short / long preamble with hostapd > If I understand correctly you say that you have stations associated to a > FreeBSD 7 ap operating in 11g and pings between the clients are slow. This > occurred w/ the Dlink AP you're trying to replace until you manually > forced short preamble. If I've got it right then this doesn't make sense > as the ap should be using short preamble unless there are non-ERP stations > on the channel. You can trace the status of short/long preamble with: > > wlandebug +assoc > > (you should get console msgs that when stations associate that indicate > whether protection is enabled). I believe you'll also get the same info > with: > > ifconfig wlan0 list sta > > on the ap. All this applies to 8.x; I've long since forgotten how things > work on 7.x and I'd recommend that if you're doing a new install you use > 8.0 and not 7.x. > > In general forcing short preamble should not have the effect you describe; > just the opposite. If you want to figure out what's really going on then > try to turn off stations that might be interfering (if possible). > Otherwise you might try moving to a different channel to avoid whatever > station is interfering. Another possibility is one or both stations are > in power save mode and there's a bug in the RELENG_7 ap support; wlandebug > +power might help for that. > > I can look at adding a knob to force short/long preamble. It would go > into HEAD though and can't promise to backport to RELENG_7. > > Sam > > Sin wrote: >> Sam, >> >> Basically I have a dlink WBR-1310 thats in bridge mode connected to my >> current BSD router ( 6.3) I'm trying to replace this 1310 product with >> FreeBSD 7. The last problem i'm dealing with is poor preformance. >> When I use my current BSD 7 setup it works, but ping times from client to >> another or even to the access point are bad. 100 - 400ms round trip. >> I had this exact problem with the 1310. The fix was to change from long >> to short preable. Been fine ever since. >> >> I used three computers to prove this before emailing. Just swapping the >> 1310 for the 7-STABLE corrects this. The 1310 uses g only mode with >> short preamble getting less then 5ms ping times to each client and host >> and vice-versa >> >> I realize that hostapd.conf is just for the encryption. However ifconfig >> and ath man pages do not talk about this setting. >> >> >> ----- Original Message ----- From: "Sam Leffler" <sam@errno.com> >> To: "Sin" <sinister@gmail.com> >> Cc: <freebsd-net@freebsd.org> >> Sent: Wednesday, September 02, 2009 11:16 AM >> Subject: Re: toggle short / long preamble with hostapd >> >> >>> Sin wrote: >>>> Hello, >>>> >>>> >>>> Does anyone know how to enable short preamble in 7-STABLE ? >>>> >>>> I'm using ath with hostapd in ap mode. It seems there was an option in >>>> hostapd.conf, but this is not in FreeBSD's >>>> /usr/share/examples/hostapd/hostapd.conf >>>> >>>> >>>> The missing hostapd.conf option was found in google: >>>> >>>> # Short Preamble >>>> # This parameter can be used to enable optional use of short preamble >>>> for >>>> # frames sent at 2 Mbps, 5.5 Mbps, and 11 Mbps to improve network >>>> performance. >>>> # This applies only to IEEE 802.11b-compatible networks and this should >>>> only be >>>> # enabled if the local hardware supports use of short preamble. If any >>>> of the >>>> # associated STAs do not support short preamble, use of short preamble >>>> will be >>>> # disabled (and enabled when such STAs disassociate) dynamically. >>>> # 0 = do not allow use of short preamble (default) >>>> # 1 = allow use of short preamble >>>> #preamble=1 >>>> >>>> >>>> my version of hostapd is " v0.5.10 " - I was not able to set this >>>> option >>> >>> On freebsd hostapd is _purely_ an authenticator; to configure 802.11 >>> parameters you use ifconfig. >>> >>>> >>>> >>>> hostapd.conf: >>>> >>>> interface=ath0 >>>> #preamble=1 >>>> debug=1 >>>> ctrl_interface=/var/run/hostapd >>>> ctrl_interface_group=wheel >>>> ssid=private >>>> wpa=1 >>>> wpa_passphrase=apassword >>>> wpa_key_mgmt=WPA-PSK >>>> wpa_pairwise=TKIP >>>> >>>> >>>> >>>> rc.conf: >>>> >>>> hostapd_enable="YES" >>>> ifconfig_ath0="mode 11g hidessid mediaopt hostap" >>>> >>>> >>>> >>>> ifconfig ath0: >>>> >>>> ath0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric >>>> 0 mtu 1500 >>>> ether 00:17:9a:4c:e7:83 >>>> media: IEEE 802.11 Wireless Ethernet autoselect mode 11g >>>> <hostap> >>>> status: associated >>>> ssid private channel 1 (2412 Mhz 11g) bssid 00:17:9a:4c:e7:83 >>>> authmode WPA privacy MIXED deftxkey 2 TKIP 2:128-bit TKIP >>>> 3:128-bit >>>> txpower 31.5 scanvalid 60 bgscan bgscanintvl 300 bgscanidle 250 >>>> roam:rssi11g 7 roam:rate11g 5 protmode CTS burst hidessid >>>> dtimperiod 1 >>> >>> In ap mode you should not manually configure preamble; it should be >>> selected according to the associated stations. What are you trying to >>> accomplish? >>> >>> Sam >>> >> >> > >
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