From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ed W Subject: Re: Need help with dialup connection (and syn packets) Date: Sat, 23 Mar 2013 21:20:19 +0000 Message-ID: <514E1C93.9080500@wildgooses.com> References: <514DD967.1080501@wildgooses.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: netfilter-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: John Lauro Cc: netfilter@vger.kernel.org Connectivity costs $1.50/minute. You pay for 20 second increments. Speed is 2.4kbits (20KB/min) It's a dial on demand router for a satellite based system Any other thoughts? I'm obviously going to look at application specific proxies, but I guess I'm hoping that someone might put me on to some clever ideas to buffer packets or duplicate them with delay... Thanks Ed W On 23/03/2013 21:11, John Lauro wrote: > Sounds like the main problem is your aggressive hangup due to > inactivity. It should be at least 4 times as the connect time, not > under half!. I suggest 6 minutes, but at least 2 minutes. > > If you can't adjust that, probably the next best alternative is a > pre-emptive ping or something to wake up the modem about 25 seconds > before you want to connect, or just ping every 5 seconds until you get > a successful response > > On Sat, Mar 23, 2013 at 12:33 PM, Ed W wrote: >> Hi, I have a dialup connection (yes they still exist) and PPP with demand >> dial. I have a problem with the exponential backoff sending new SYN packets >> when creating a new tcp connection. The problem is that the dialup >> connection takes around 23 seconds to complete (and then hangs up 10 seconds >> later due to inactivitity), but by then the gaps between SYN packets is very >> long... >> >> Unfortunately most operating systems send an initial SYN, then exponentially >> backoff with intermittent resends, say after 1 sec, 2 secs, 4 secs, 8 secs, >> 16 secs, etc. So what we observe is that because the dialup connection >> takes so long to complete, by then the tcp connection is only trying quite >> intermittently to connect, eg you might well wait another 8+ seconds before >> the next syn is resent, quite easily my demand dial connection will hangup >> before the retransmit is even fired... >> >> Does anyone have any suggestions on how I might fake this a little? I >> effectively desire to simulate buffering syn packets before the PPP >> connection comes up? >> >> Thanks for any off the wall thoughts... >> >> Ed W >> -- >> To unsubscribe from this list: send the line "unsubscribe netfilter" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html