From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nm6-vm6.access.bullet.mail.gq1.yahoo.com ([216.39.63.154]:32860 "EHLO nm6-vm6.access.bullet.mail.gq1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752813AbcCGQ7n (ORCPT ); Mon, 7 Mar 2016 11:59:43 -0500 Date: Mon, 07 Mar 2016 08:53:28 -0800 Subject: Re: [6lo] big frame support in 802.15.4G From: Don Sturek Message-ID: References: <20160228140659.GA17980@omega> <28981.1457015214@obiwan.sandelman.ca> <20160304083528.GA1525@omega> <24416.1457106776@obiwan.sandelman.ca> <20160304163749.GA21798@omega> <18168.1457123400@obiwan.sandelman.ca> <56DC2A0A.6070906@htt-consult.com> <4538.1457367913@obiwan.sandelman.ca> In-Reply-To: <4538.1457367913@obiwan.sandelman.ca> Mime-version: 1.0 Content-type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit Sender: linux-wpan-owner@vger.kernel.org List-ID: To: Michael Richardson , Robert Moskowitz Cc: Alexander Aring , linux-wpan@vger.kernel.org, 6lo@ietf.org Hi Michael, I was not clear on what you were asking. Here are a couple of points: 1) IEEE 802.15.4g was an amendment to IEEE 802.15.4-2011 where the main contributions were to the PHY (not so much the MAC). There is nothing in 4g that would make it incompatible with IEEE 802.15.4-2011 2) IEEE 802.15.4-2011 has a field called "frame version" that denotes special processing for the 2003, 2006 and 2011 versions of the specification. That is one place where a packet may be dropped but that would not apply to MAC versions that are based on 2011 alone 3) If you were asking whether a 4g MAC/PHY implementation could send payloads of varying sizes then I think the answer is "yes" with the following caveats: I. Since IEEE 802.15.4 never had a propoer protocol dispatch until IEEE 802.15.9 came along, there would have to be some special vendor extensions to denote where a full IPv6 frame was present or when a 6LoWPAN fragment was present. It is possible with the Multiplex ID/EtherType in IEEE 802.15.9 to make that distinction. I think in some implementations you would see a varying payload size. For example, when transferring packets over a good radio link, the payload size might be set to 1280 bytes or better and a full IPv6 frame would be present. In cases where the link is poor, the two communicating devices may choose to use shorter packets and 6LoWPAN to fragment/reassemble, however, keep in mind there are only MAC retries to ensure delivery. Don On 3/7/16 8:25 AM, "6lo on behalf of Michael Richardson" <6lo-bounces@ietf.org on behalf of mcr+ietf@sandelman.ca> wrote: > >Robert Moskowitz wrote: > > The difference is in the header bits. A 802.15.4-2011 device would >see > > the bits set in the header that 4g uses and drop the packet > > immediately. Pat would have to pipe in here, and there may be some > > issues around super frames and intergap timings that result in > > interesting behaviour, better to be avoided. > >Right, but the question is: > >1) is it physically possible for a 15.4g device to send both 15.4g > frames and 15.4-2011 frames? > Another email suggests that this can never happen because frequencies > are never the same. If so, end of problem. > >2) if the answer to question 1 is yes, then 15.4g devices need to know > if they are speaking to 15.4-2011 devices, and > a) adjust their frame header bits appropriately. > b) to 6lowpan fraglettation. > > >-- >Michael Richardson , Sandelman Software Works > -= IPv6 IoT consulting =- > > > >_______________________________________________ >6lo mailing list >6lo@ietf.org >https://www.ietf.org/mailman/listinfo/6lo