From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from tuna.sandelman.ca (unknown [IPv6:2607:f0b0:f:3:216:3eff:fe7c:d1f3]) by huchra.bufferbloat.net (Postfix) with ESMTP id 62B6921F166 for ; Sun, 6 Jan 2013 17:35:19 -0800 (PST) Received: from sandelman.ca (unknown [IPv6:2607:f0b0:f:2::247]) by tuna.sandelman.ca (Postfix) with ESMTP id EFCD72016D; Sun, 6 Jan 2013 20:39:26 -0500 (EST) Received: by sandelman.ca (Postfix, from userid 179) id 2785D636C7; Sun, 6 Jan 2013 20:34:31 -0500 (EST) Received: from sandelman.ca (localhost [127.0.0.1]) by sandelman.ca (Postfix) with ESMTP id 176C5636C3; Sun, 6 Jan 2013 20:34:31 -0500 (EST) From: Michael Richardson To: davecb@spamcop.net In-Reply-To: <50E6F076.4070403@rogers.com> References: <50E6F076.4070403@rogers.com> X-Mailer: MH-E 8.3; nmh 1.3-dev; XEmacs 21.4 (patch 22) X-Face: $\n1pF)h^`}$H>Hk{L"x@)JS7<%Az}5RyS@k9X%29-lHB$Ti.V>2bi.~ehC0; <'$9xN5Ub# z!G,p`nR&p7Fz@^UXIn156S8.~^@MJ*mMsD7=QFeq%AL4m Sender: mcr@sandelman.ca Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] wifi AP switching time X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Jan 2013 01:35:19 -0000 I asked > A comment was made a month ago or so about how long it takes wifi APs > to switch from transmitting (unicast) to one station to another. That > there was quite a large latency here, and that this was one reason that > the AP designers wanted large buffers to accmulate, so that the > switching time could be amortized over a larger number of packets. Pedro Tumusok replied > I might be way of here, but to me this sounds like a-mpdu which is > used to aggregate frames to get higher throughput. Thats in the > specification, its > in 802.11ac and I believe that it go introduced with 802.11n. > > It is there to mitigate the overhead of aquiring the channel. Does this mean that 802.11a,b do not suffer from this problem? -- ] Never tell me the odds! | ipv6 mesh networks [ ] Michael Richardson, Sandelman Software Works | network architect [ ] mcr@sandelman.ca http://www.sandelman.ca/ | ruby on rails [