toggle short / long preamble with hostapd

[Sin]

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 at errno.com>
To: "Sin" <sinister at gmail.com>
Cc: <freebsd-net at 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
>