On Tue, Mar 13, 2007 at 08:05:12PM +0000, Richard Stearn wrote: > Greetings all > > I am in the process of creating a wireshark dissector for APRS. My > primary information source to date has been the APRS 1.01 spec, > supplemented by the 1.1 & 1.2 errata. > > I note when analysing packet captures that many of the position, > object & item packets do not comform to the specification. Is this > me misreading the specification or what?
Sanctifying APRS by calling it "protocol" is a bit much, but there are published specifications, and then there are experience based implementations that work more often... The APRS is a collection of ad-hoc message encodings without any sort of coherent protocol-id at wrapping AX.25 header. Using "this is UI frame" tagging at AX.25 level does not embed any sort of data about the protocol inside it. Even TCP/IP in AX.25 UI frame has a sort of protocol ID, but APRS does not. Nobody has bothered to specify one at day one, and now it is way too late.. There are couple excellent perl engines to decode APRS positions including MICe compressed variants. > Thoughts please. > -- > Regards > Richard 73 de Matti, OH2MQK - To unsubscribe from this list: send the line "unsubscribe linux-hams" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
