| Message ID | 1423568924-11895-1-git-send-email-michal.kazior@tieto.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Johannes Berg |
| Headers | show |
On Tue, 2015-02-10 at 12:48 +0100, Michal Kazior wrote: > Some APs experience problems when working with > U-APSD. Decreasing the probability of that > happening by using legacy mode for all ACs but VO > isn't enough. > > Cisco 4410N originally forced us to enable VO by > default only because it treated non-VO ACs as > legacy. > > However some APs (notably Netgear R7000) silently > reclassify packets to different ACs. Since u-APSD > ACs require trigger frames for frame retrieval > clients would never see some frames (e.g. ARP > responses) or would fetch them accidentally after > a long time. This makes me a little sad, but I've applied this and even added a Cc stable tag due to the interoperability issues. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Mar 3, 2015 at 2:46 PM, Johannes Berg <johannes@sipsolutions.net> wrote: > On Tue, 2015-02-10 at 12:48 +0100, Michal Kazior wrote: >> Some APs experience problems when working with >> U-APSD. Decreasing the probability of that >> happening by using legacy mode for all ACs but VO >> isn't enough. >> >> Cisco 4410N originally forced us to enable VO by >> default only because it treated non-VO ACs as >> legacy. >> >> However some APs (notably Netgear R7000) silently >> reclassify packets to different ACs. Since u-APSD >> ACs require trigger frames for frame retrieval >> clients would never see some frames (e.g. ARP >> responses) or would fetch them accidentally after >> a long time. > > This makes me a little sad, but I've applied this and even added a Cc > stable tag due to the interoperability issues. > Mixed mode (uapsd + legacy) is not really the optimal configuration, where we expect STA to send trigger frames periodically to retrieve the DL packets (especially very first packet). But still if we want power save, i suggest going for All u-apsd (0xF), so that AP will inform us by setting the TIM bit and we can retrieve the first frame. (We have this patch internally and it works well). -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> >> Cisco 4410N originally forced us to enable VO by > >> default only because it treated non-VO ACs as > >> legacy. > Mixed mode (uapsd + legacy) is not really the optimal > configuration, where we expect STA to send trigger frames periodically > to retrieve the DL packets (especially very first packet). > > But still if we want power save, i suggest going for > All u-apsd (0xF), so that AP will inform us by setting the TIM bit > and we can retrieve the first frame. > (We have this patch internally and it works well). Except where it doesn't work, like on the Cisco 4410N - see above. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Mar 3, 2015 at 3:06 PM, Johannes Berg <johannes@sipsolutions.net> wrote: > >> >> Cisco 4410N originally forced us to enable VO by >> >> default only because it treated non-VO ACs as >> >> legacy. > >> Mixed mode (uapsd + legacy) is not really the optimal >> configuration, where we expect STA to send trigger frames periodically >> to retrieve the DL packets (especially very first packet). >> >> But still if we want power save, i suggest going for >> All u-apsd (0xF), so that AP will inform us by setting the TIM bit >> and we can retrieve the first frame. >> (We have this patch internally and it works well). > > Except where it doesn't work, like on the Cisco 4410N - see above. But for that single AP, we are forced to lose efficient power savings unless user configured explicitly. -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 3 March 2015 at 11:15, Krishna Chaitanya <chaitanya.mgit@gmail.com> wrote: > On Tue, Mar 3, 2015 at 3:06 PM, Johannes Berg <johannes@sipsolutions.net> wrote: >> >>> >> Cisco 4410N originally forced us to enable VO by >>> >> default only because it treated non-VO ACs as >>> >> legacy. >> >>> Mixed mode (uapsd + legacy) is not really the optimal >>> configuration, where we expect STA to send trigger frames periodically >>> to retrieve the DL packets (especially very first packet). >>> >>> But still if we want power save, i suggest going for >>> All u-apsd (0xF), so that AP will inform us by setting the TIM bit >>> and we can retrieve the first frame. >>> (We have this patch internally and it works well). >> >> Except where it doesn't work, like on the Cisco 4410N - see above. > But for that single AP, we are forced to lose efficient power savings > unless user configured explicitly. Correct me if I'm wrong, but u-APSD makes sense only if you have userspace apps aware of it. I don't know any. VoIP traffic uses and it works just because it generate bi-directional traffic in most cases so you have implicit trigger frames generated when you Tx, but that's probably as far as the practical use-case goes, no? You'd still need netfilter rules to reclassify your traffic anyway, wouldn't you? If you mainly wait for data you need to send trigger frames periodically and only userspace app knows what Rx latency is tolerated (that's why relying on driver/firmware auto-trigger generation doesn't cut it). Anyway I don't think you can ask users to do the opposite (i.e. disable u-APSD if they experience problems with APs). Wi-Fi should Just Work. Joys of IOT.. Micha? -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Mar 3, 2015 at 3:58 PM, Michal Kazior <michal.kazior@tieto.com> wrote: > On 3 March 2015 at 11:15, Krishna Chaitanya <chaitanya.mgit@gmail.com> wrote: >> On Tue, Mar 3, 2015 at 3:06 PM, Johannes Berg <johannes@sipsolutions.net> wrote: >>> >>>> >> Cisco 4410N originally forced us to enable VO by >>>> >> default only because it treated non-VO ACs as >>>> >> legacy. >>> >>>> Mixed mode (uapsd + legacy) is not really the optimal >>>> configuration, where we expect STA to send trigger frames periodically >>>> to retrieve the DL packets (especially very first packet). >>>> >>>> But still if we want power save, i suggest going for >>>> All u-apsd (0xF), so that AP will inform us by setting the TIM bit >>>> and we can retrieve the first frame. >>>> (We have this patch internally and it works well). >>> >>> Except where it doesn't work, like on the Cisco 4410N - see above. >> But for that single AP, we are forced to lose efficient power savings >> unless user configured explicitly. > > Correct me if I'm wrong, but u-APSD makes sense only if you have > userspace apps aware of it. I don't know any. VoIP traffic uses and it > works just because it generate bi-directional traffic in most cases so > you have implicit trigger frames generated when you Tx, but that's > probably as far as the practical use-case goes, no? You'd still need > netfilter rules to reclassify your traffic anyway, wouldn't you? If > you mainly wait for data you need to send trigger frames periodically > and only userspace app knows what Rx latency is tolerated (that's why > relying on driver/firmware auto-trigger generation doesn't cut it). Agree u-apsd is tightly coupled with the applications. But there is a provision in the protocol to deliver buffered frames without sending explicit triggers (which is quite waste of tx power). So it might be optimized for each application, but overall it will not break the functionality for those drivers who do not send explicit triggers frames periodically. Even for unidirectional protocol has a provison when All AC's are delivery enabled, it will still set the TIM bit, so using which we can start sending trigger frames. So either disabling/enabling u-apsd is fine aslong as we do it for all AC's together, mixed mode is useless. > > Anyway I don't think you can ask users to do the opposite (i.e. > disable u-APSD if they experience problems with APs). Wi-Fi should > Just Work. Joys of IOT.. May be in utopia ;-).
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h index 3afe368..c0e089c 100644 --- a/net/mac80211/ieee80211_i.h +++ b/net/mac80211/ieee80211_i.h @@ -58,13 +58,24 @@ struct ieee80211_local; #define IEEE80211_UNSET_POWER_LEVEL INT_MIN /* - * Some APs experience problems when working with U-APSD. Decrease the - * probability of that happening by using legacy mode for all ACs but VO. - * The AP that caused us trouble was a Cisco 4410N. It ignores our - * setting, and always treats non-VO ACs as legacy. + * Some APs experience problems when working with U-APSD. Decreasing the + * probability of that happening by using legacy mode for all ACs but VO isn't + * enough. + * + * Cisco 4410N originally forced us to enable VO by default only because it + * treated non-VO ACs as legacy. + * + * However some APs (notably Netgear R7000) silently reclassify packets to + * different ACs. Since u-APSD ACs require trigger frames for frame retrieval + * clients would never see some frames (e.g. ARP responses) or would fetch them + * accidentally after a long time. + * + * It makes little sense to enable u-APSD queues by default because it needs + * userspace applications to be aware of it to actually take advantage of the + * possible additional powersavings. Implicitly depending on driver autotrigger + * frame support doesn't make much sense. */ -#define IEEE80211_DEFAULT_UAPSD_QUEUES \ - IEEE80211_WMM_IE_STA_QOSINFO_AC_VO +#define IEEE80211_DEFAULT_UAPSD_QUEUES 0 #define IEEE80211_DEFAULT_MAX_SP_LEN \ IEEE80211_WMM_IE_STA_QOSINFO_SP_ALL
Some APs experience problems when working with U-APSD. Decreasing the probability of that happening by using legacy mode for all ACs but VO isn't enough. Cisco 4410N originally forced us to enable VO by default only because it treated non-VO ACs as legacy. However some APs (notably Netgear R7000) silently reclassify packets to different ACs. Since u-APSD ACs require trigger frames for frame retrieval clients would never see some frames (e.g. ARP responses) or would fetch them accidentally after a long time. It makes little sense to enable u-APSD queues by default because it needs userspace applications to be aware of it to actually take advantage of the possible additional powersavings. Implicitly depending on driver autotrigger frame support doesn't make much sense. Signed-off-by: Michal Kazior <michal.kazior@tieto.com> --- net/mac80211/ieee80211_i.h | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-)