appears to have no flexibility to do this and there are no version
fields in the frame structure so it can't be made backwards compatible.
The design ought to have had this built in, but seems not to have
considered doing it.

The exact same stupidity has long crippled the advancement of the
AX.25 protocol, and the APRS protocol, and nearly every other *amateur*
designed protocol.

Worse, AX.25 was coded into law (in the USA, and elsewhere), thus
preventing any other air protocols from even having a chance because
they could not be used, or used unattended, such as a BBS.

D*Star apparently has the same problem - it's a lot like commercial P25
(or MotoTRBO), but it's a lot different too, and there's really no way
to fix that.

And how about all those surplus TETRA radios? Yah, the USA can't currently
use TETRA for commercial/industrial radio, but the rest of the world does
and there's nothing stopping USA hams from doing so.

I sure would like to see someone make an off-the-shelf digital voice ham
radio that made use of openly-available codecs, especially if they were
flashable.

AX.25's other remaining use, that of carrying tcp/ip, has also got a
real problem: the minimum IPv6 packet is bigger than the maximum AX.25
packet. Oops.
- Brian

Brian Kantor wrote:
The exact same stupidity has long crippled the advancement of the
AX.25 protocol, and the APRS protocol, and nearly every other *amateur*
designed protocol.

Fortunately there were a couple of unused bits in the AX.25 header
that were used for AX.25 v2, DAMA, and Extended Sequence numbers.
But more flexibility would certainly have been welcome.

AX.25's other remaining use, that of carrying tcp/ip, has also got a
real problem: the minimum IPv6 packet is bigger than the maximum AX.25
packet. Oops.

There is a segmentation protocol at AX.25 level (defined by Phil Karn
and used in NET/NOS) that allows the segmentation of a single IP datagram
over multiple AX.25 frames.

With a new PID it could be used for IPv6 over AX.25.

Of course, the headers of IPv4 are already considered big in the
amateur packet radio world. At the datarates typically used, one
wants to conserve on header size.

Rob wrote:
Of course, the headers of IPv4 are already considered big in the
amateur packet radio world. At the datarates typically used, one
wants to conserve on header size.

Yes, some have tried using Van Jacobsen header prediction to cut down
on the size of the actual transmitted header - a rather nice solution,
but not really workable in a lossy datagram world.

So far the best method seems to be (using a separate pid) an adaptation
of the SLIP with compression and header prediction over a connected-mode
(i.e, reliable stream). This adds packet framing and reduces the overhead
a bit, and at 9600 bps or faster, is actually slightly faster than a
carrier pigeon. It also places the burden of retries on the air link
where it belongs, rather than end-to-end, which is clearly the wrong
place to do it.

A number of F-S-U folks have been doing some very interesting work in
real high-speed packet (230 kb/s or faster, some multi-Mb/s), and
such links would easily support digital voice without much need for
super-bandwidth-conserving codecs.

GSM and similar codecs are now easily available in software
implementations; these work quite well at an air rate of 9600 or
sometimes less. Some are free of significant encumbrances that
would hinder widespread usage.

In the land mobile radio regime, the ultimate goal is to reduce the
consumed bandwidth so as to stack more customers in the same band.
Hams have no such need; if anything we have (shhh!) more bandwidth than
we need on the VHF and up bands, so using extremely narrowband codecs
just isn't something we need to do.
- Brian

In message , Yeti
writes
On 25/09/2010 11:04, Rob wrote:

We should develop an open space rocket to propel our geostationary OSCAR
into space. Sure.

A Geostationary OSCAR - what a terrible idea!

With enough power and weak signal modes you can use the geostationary
broadcast satellites as passive reflectors .

DIJ
--
Brian Howie

I just don't like D STAR and I don't LIKE ICOM

I
Can
Only
Monitor

D Star is nothing but a copy cat attempt to try to make amateur radio more like public service.

In the hills of western Pennsylvania, it does not work! Period!

Maybe if all your emergencies were within 5 miles of the repeater, and everything was wiped off the face of the earth, except your D Star Repeater, it might work. But that does not happen in the real world.

Please, let D Star die a death of natural causes.
It has no place in amateur radio, except for the LIDS who wants to be different. Does it have interoptibility - NO, if your transceiver is analog - you are SOL - so why use it?

Once people progresses beyond the stage of 2 meters, playing around with walkie talkies, and moves up to HF, the thought of wanting to go back to two meters is almost ludrichrist for anything other then doing local ecomm work.