markus@infoscape.com wrote: > > Thomas Wuensche writes: > > Of course it is possible to put a TCP/IP protocol stack onto CAN, > > however this is not used very much - CAN is used in the automotive > > and industrial automation field, and the applications taking > > benefit from CAN mostly use other protocols. > > Can you give a brief description of how TCP/IP is implemented on CAN? > I always thought the the main advantage of CAN was the automatic > collision detection/resolution that was implemented in hardware. To a > certain extent, this also buys you some guarantees about the available > bandwidth for each different type of service. My understanding is, > that this requires specially formated device IDs at the beginning of > each datagram. Do IP packets get encapsulated within CAN packets or do > people forgo the advantages of the CAN protocol and directly send IP > frames (or more likely, ethernet frames) onto the wire? CAN does use COB-IDs (Communication Object IDs) in the beginning of a data frame. The COB-ID indicates the content of the frame (and only implicitly the sender, since content like a temperature value regularly comes from the temperature sensing device). The COB-ID furthermore is used as priority for the loss-free collision detection/ resolution. CAN is a broadcast system, so every node can listen to frames from other nodes. Implementing TCP/IP on top of CAN will definitely use the CAN frames, because this is all the (hardware) CAN controllers can handle. You could use one COB-ID for the TCP/IP frames sent by a node. You would break a TCP/IP frame into small hunks of 7 (or 8 ?) bytes and send these in sequence using the selected COB-ID, thus effectively broad- casting a sequence of bytes. Any other node can assemble the packets and interpret them as datagram. This approach should be similar with what is done to break down an IP packet into ATM cells. Regarding the characteristics (bandwidth etc) you would not take this approach as a general network connection between desktop PCs. However it may be reasonable, if TCP/IP needs to be carried on a network besides control related data, if you have harsh environment or if you have long distances at low speed requirements (50kbit/s at 1000m). Hope this helps. If you need more information on CAN, please have at look at our website. A description of details of the CAN protocol is available there. Thomas Wuensche > Markus > > -- > Markus Gutschke Internet: markus@infoscape.com > Infoscape, Inc Phone: +1-415-544-4762 > 100 Broadway, 2nd floor > San Francisco, CA 94111 > > Disclaimer: The above message represents my personal opinion; It does > not constitute an offical statement by Infoscape! > > -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > > Part 1.2 Type: application/pgp-signature > Encoding: 7bit -- ------------------------------------------------------- EMS Dr. Thomas Wuensche Phone: +49-8441-490260 Fax +49-8441-81860 Visit also our web-site at http://www.ems-wuensche.com/ ------------------------------------------------------- =========================================================================== This Mail was sent to netboot mailing list by: Thomas Wuensche <wuensche@ems-wuensche.com> To get help about this list, send a mail with 'help' as the only string in it's body to majordomo@baghira.han.de. If you have problems with this list, send a mail to netboot-owner@baghira.han.de.
For requests or suggestions regarding this mailing list archive please write to netboot@gkminix.han.de.