Re: [RFC V2] cfg80211: introduce critical protocol indication from user-space

[Ben Greear <greearb@candelatech.com>]

On 03/28/2013 03:42 PM, Dan Williams wrote:
> On Thu, 2013-03-28 at 22:28 +0100, Johannes Berg wrote:
>> On Thu, 2013-03-28 at 22:16 +0100, Arend van Spriel wrote:
>>>> That seems pretty long? Why have such a long *minimum* duration? At 2.5
>>>> seconds, it's way long, and then disabling most of the
>>>> protections/powersave/whatever no longer makes sense for this period of
>>>> time since really mostly what this does will be reducing the wifi
>>>> latency.
>>
>>> Ok, so what minimum do you (or someone else can chime in here) think a
>>> DHCP exchange takes as that was considered a likely protocol that can
>>> benefit from this API.
>>
>> Well, you can do DHCP a second or so, I'd think? And EAPOL much quicker,
>> of course. I don't really see any reasonable minimum time? We might want
>> to enforce a max though, maybe.
>
> Not quite.  A lot is dependent on the server itself, and I've had users
> on university and corporate networks report it sometimes takes 30 to 60
> seconds for the whole DHCP transaction to complete (DISCOVER, REQUEST,
> OFFER, ACK).  Sometimes there's a NAK in there if the server doesn't
> like your lease, which means you need another round-trip.  So in many
> cases, it's a couple round-trips and each of these packets may or may
> not get lost in noisy environments.

Anyone know if DHCP requests and responses go to the high-priority
queue in the NIC by default?  Seems like that might be a big help if not...

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com