Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1S7aDm-0000nP-Gp for bitcoin-development@lists.sourceforge.net; Tue, 13 Mar 2012 22:29:34 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 74.125.82.175 as permitted sender) client-ip=74.125.82.175; envelope-from=mh.in.england@gmail.com; helo=mail-we0-f175.google.com; Received: from mail-we0-f175.google.com ([74.125.82.175]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1S7aDl-00070O-Nu for bitcoin-development@lists.sourceforge.net; Tue, 13 Mar 2012 22:29:34 +0000 Received: by wera1 with SMTP id a1so1480886wer.34 for ; Tue, 13 Mar 2012 15:29:27 -0700 (PDT) MIME-Version: 1.0 Received: by 10.180.80.35 with SMTP id o3mr697802wix.5.1331677767581; Tue, 13 Mar 2012 15:29:27 -0700 (PDT) Sender: mh.in.england@gmail.com Received: by 10.216.162.66 with HTTP; Tue, 13 Mar 2012 15:29:27 -0700 (PDT) In-Reply-To: <201203131445.09552.luke@dashjr.org> References: <201203131445.09552.luke@dashjr.org> Date: Tue, 13 Mar 2012 23:29:27 +0100 X-Google-Sender-Auth: eyp2sE7txBfHvOMT39oz4C80Luw Message-ID: From: Mike Hearn To: Luke-Jr Content-Type: text/plain; charset=UTF-8 X-Spam-Score: -1.0 (-) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (mh.in.england[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.5 AWL AWL: From: address is in the auto white-list X-Headers-End: 1S7aDl-00070O-Nu Cc: bitcoin-development@lists.sourceforge.net Subject: Re: [Bitcoin-development] Adding a pong message X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 13 Mar 2012 22:29:34 -0000 TCP keep-alives aren't reliably implemented. I've got reports that sometimes we struggle to keep connection to the network on mobile, eg, because we roam into an area with poor connectivity but not poor enough for the network stack to drop access entirely. Being able to quickly check if the connection is really there with some kind of bounded, app layer deadline is probably useful and besides, it's cheap.