Hi Dirk.
>> In fact, the HDLC standard on which it is based already defines
>> how such a system is to be handled, and precicely what should
>> occur under all possible scenarios, so there's very little to be
>> agreed on other than precicely what is meant by "Extended mode"
>> as opposed to "non-extended mode".
>> If you have access to the ISO standard for HDLC, look up the
>> diagrams relating to negotiations between systems supporting
>> both SABM and SABME modes to see the various possible timing
>> diagrams, together with when the negotiation should result in
>> SABM being agreed, and when it should result in SABME being
>> agreed. Also in the same document are the timing diagrams for
>> when one end is SABM and SABME capable, but the other only
>> supports SABM, so that is dealt with as well.
> erm.. I thought that the whole point of ISO layering was that
> the level 1 layer (which I presume to be HDLC) has nothing to do
> with the level 2 layer (in this case (A)X25).
Actually, HDLC is level 2, and AX.25 is a variant of HDLC that uses
the "Extended address field" as defined in the HDLC standard, but
otherwise is little more than pure HDLC.
The level 1 protocols are adequately defined by the V.24 standard,
also known in some parts of the world as RS.232.C if that helps.
> So why are we confusing HDLC signalling (which is based on one
> or more 'flag' bytes, some (optionally bit stuffed) octets of
> data, a CRC and one or more flag bytes with some spurious layer
> of protocol which may (or may not) be imposed on top of it?
> AX25 works just as well in raw ethernet II frames on a wire or
> mpt1327 codewords on radio as it does with HDLC.
Since AX.25 level 2 is HDLC, where's the confusion? Nobody so far has
confused it with either AX.25 level 3 or any of the other level 3
protocols such as ethernet II, other than possibly your good self.
Best wishes from Riley.
+----------------------------------------------------------------------+
| There is something frustrating about the quality and speed of Linux |
| development, ie., the quality is too high and the speed is too high, |
| in other words, I can implement this XXXX feature, but I bet someone |
| else has already done so and is just about to release their patch. |
+----------------------------------------------------------------------+
* ftp://ftp.MemAlpha.cx/pub/rhw/Linux
* http://www.MemAlpha.cx/kernel.versions.html
