From MAILER-DAEMON Mon Sep 12 06:33:13 2011 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1R33pB-0007bR-Gh for mharc-uracoli-devel@gnu.org; Mon, 12 Sep 2011 06:33:13 -0400 Received: from eggs.gnu.org ([140.186.70.92]:45601) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R33p8-0007bG-TE for uracoli-devel@nongnu.org; Mon, 12 Sep 2011 06:33:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1R33p7-0003aM-Va for uracoli-devel@nongnu.org; Mon, 12 Sep 2011 06:33:10 -0400 Received: from mail-fx0-f45.google.com ([209.85.161.45]:64641) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R33p7-0003a2-R1 for uracoli-devel@nongnu.org; Mon, 12 Sep 2011 06:33:09 -0400 Received: by fxh13 with SMTP id 13so1710035fxh.4 for ; Mon, 12 Sep 2011 03:33:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=sender:date:from:to:subject:message-id:mime-version:content-type :content-disposition:user-agent; bh=0OsVq0NKIMybRkSb+fM2mJinKa0KrMV06vU0BRzw4es=; b=Q5vB3hChujNB3ZaLrrHKaYgeiglVQC+nNi1KGtUE+V/c80xi9Mt6FBSmA6nVkLZsEU tjNa7wxP2kcD6vAyVeGJAVasnS8k1bgTOfroa6VqXbFYnYoS02n6ZvCnVTvEg1Kguryn geDahwVHCEBxsgiqc0wOJt29a2DBDCE4D/X74= Received: by 10.223.28.72 with SMTP id l8mr132266fac.137.1315823588056; Mon, 12 Sep 2011 03:33:08 -0700 (PDT) Received: from localhost (jem75-13-78-235-252-247.fbx.proxad.net [78.235.252.247]) by mx.google.com with ESMTPS id o22sm5197132fab.11.2011.09.12.03.33.06 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 12 Sep 2011 03:33:06 -0700 (PDT) Sender: Charles Goyard Date: Mon, 12 Sep 2011 12:36:47 +0200 From: Charles Goyard To: uracoli-devel@nongnu.org Message-ID: <20110912103647.GA4692@tip> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 2) X-Received-From: 209.85.161.45 Subject: [uracoli-devel] General question about large payloads X-BeenThere: uracoli-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussion of the uracoli development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 12 Sep 2011 10:33:11 -0000 Hi all, on a application, I use a 52 bytes-long payload (command+parameter for the 50 balls+EOL). At some point I will want to extend that to 100 objects. Would it then be better to send one large packet with a 102-bytes payload, or to break it into smaller pieces ? Better is to understand from a "probability to get a large packet unaltered". Just wondering. Thanks, Charles From MAILER-DAEMON Mon Sep 12 17:10:14 2011 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1R3Dle-0000Sg-Pu for mharc-uracoli-devel@gnu.org; Mon, 12 Sep 2011 17:10:14 -0400 Received: from eggs.gnu.org ([140.186.70.92]:48940) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R3Dlc-0000SU-Q3 for uracoli-devel@nongnu.org; Mon, 12 Sep 2011 17:10:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1R3Dla-00072i-W1 for uracoli-devel@nongnu.org; Mon, 12 Sep 2011 17:10:12 -0400 Received: from uriah.heep.sax.de ([213.240.137.9]:46920) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R3Dla-00071q-OB for uracoli-devel@nongnu.org; Mon, 12 Sep 2011 17:10:10 -0400 Received: by uriah.heep.sax.de (Postfix, from userid 107) id 1841B59; Mon, 12 Sep 2011 23:10:07 +0200 (MET DST) Date: Mon, 12 Sep 2011 23:10:07 +0200 From: Joerg Wunsch To: uracoli-devel@nongnu.org Message-ID: <20110912211007.GR45024@uriah.heep.sax.de> References: <20110912103647.GA4692@tip> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110912103647.GA4692@tip> X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E X-GPG-Fingerprint: 5E84 F980 C3CA FD4B B584 1070 F48C A81B 69A8 5873 User-Agent: Mutt/1.5.20 (2009-06-14) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 213.240.137.9 Subject: Re: [uracoli-devel] General question about large payloads X-BeenThere: uracoli-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list Reply-To: Joerg Wunsch List-Id: Discussion of the uracoli development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 12 Sep 2011 21:10:13 -0000 As Charles Goyard wrote: > At some point I will want to extend that to 100 objects. Would it > then be better to send one large packet with a 102-bytes payload, or > to break it into smaller pieces ? Better is to understand from a > "probability to get a large packet unaltered". Of course, the longer the packet, the higher the chance that one bit might be corrupted, so the entire packet has to be retransmitted. However, in practice, that will probably only become an issue if you're already working at the brink of the link budget. Remember, there's already quite a bit of redundancy in the normal IEEE 802.15.4 signal, which allows for signals to be detected 10 dB (or a little more) below the noise level. For your flying balls, I guess there will probably be short moments where you might get failed transmissions, but that should be covered still well in time using the normal packet retransmission procedure, as the flying ball quickly leaves the spot of the bad transmission path again. With a 102-byte payload, just keep an eye on the MAC-layer overhead, to not exceed the maximal packet size (127 octets). With two octets of FCF, one octet sequence number, two octets FCS (CRC-16), and assuming two long addresses without PAN ID compression, the MAC overhead would already become 25 octets, thus just reaching the maximum packet size. Of course, you'd normally use short addresses, and also PAN ID compression, saving you another 14 octets. -- cheers, J"org .-.-. --... ...-- -.. . DL8DTL http://www.sax.de/~joerg/ NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)