On Mon, 11 Oct 2021 08:35:07 +0200, Oleksij Rempel wrote: > On Sat, Oct 09, 2021 at 04:43:56PM +0800, Zhang Changzhong wrote: > > On 2021/10/8 19:00, Oleksij Rempel wrote: > > > On Fri, Oct 08, 2021 at 05:22:12PM +0800, Zhang Changzhong wrote: > > >> Hi Kurt, > > >> Sorry for the late reply. > > >> > > >> On 2021/9/30 15:42, Kurt Van Dijck wrote: > > >>> On Thu, 30 Sep 2021 11:33:20 +0800, Zhang Changzhong wrote: > > >>>> According to SAE-J1939-21, the data length of TP.DT must be 8 bytes, so > > >>>> cancel session when receive unexpected TP.DT message. > > >>> > > >>> SAE-j1939-21 indeed says that all TP.DT must be 8 bytes. > > >>> However, the last TP.DT may contain up to 6 stuff bytes, which have no meaning. > > >>> If I remember well, they are even not 'reserved'. > > >> > > >> Agree, these bytes are meaningless for last TP.DT. > > >> > > >>> > > >>>> [...] > > >>> > > >>> I think this is a situation of > > >>> "be strict on what you send, be tolerant on what you receive". > > >>> > > >>> Did you find a technical reason to abort a session because the last frame didn't > > >>> bring overhead that you don't use? > > >> > > >> No technical reason. The only reason is that SAE-J1939-82 requires responder > > >> to abort session if any TP.DT less than 8 bytes (section A.3.4, Row 7). > > > > > > Do you mean: "BAM Transport: Ensure DUT discards BAM transport when > > > TP.DT data packets are not correct size" ... "Verify DUT discards the > > > BAM transport if any TP.DT data packet has less than 8 bytes"? > > > > Yes. > > OK, then I have some problems to understand this part: > - 5.10.2.4 Connection Closure > The “connection abort” message is not allowed to be used by responders in the > case of a global destination (i.e. BAM). > > My assumption would be: In case of broadcast transfer, multiple MCU are > receivers. If one of MCU was not able to get complete TP.DT, it should > not abort BAM for all. There is indeed no action defined to abort at BAM. > > So, "DUT discards the BAM transport" sounds for me as local action. > Complete TP would be dropped locally. exact. Kurt
