Rud Merriam wrote: > I suggest anyone interested in this topic start by reading > http://citeseer.ist.psu.edu/cache/papers/cs/2504/http:zSzzSzpeople.qualcomm. > com/karnz/papers/newlinkpaper.pdf/karn94toward.pdf by Phil Karn > KA9Q. If anyone does not recognize his name or call then research him > because he is an icon in amateur packet and digital communications. > One of the "experts". Just to tease the article starts by saying that > AX.25 "is widely recognized as far from optimal." There are some > additional articles by Phil and others that address the issues with > AX.25, including the hidden transmitter problem.
OK, I will try to get this or the other links. I only have mail at home, and I am on holidays. Of course I know about Phil Karn. I have been an AMSAT-NA Life Member for 28 years and a licensed ham for 36 years. I am also aware that AX.25 is far from optimal, but so far it works. Tearing it all down and redoing or substituting looks scary at the present perspective. It would trash most TNC's and packet software in developed and developing countries, those that do not have the Internet as available as tap water. Would that be fruitful? > You mention protocol layers. Which model do you want to use for > discussion, OSI or the Internet model? Perhaps not a big question > since layers 1 & 2 are the same but once we start moving up the stack > they differ. I have been speaking about the seven layer OSI model. It is the relevant one for AX.25. I quote for reference: "This protocol conforms to International Standards Organization (ISO) Information Standards (IS) 3309, 4335 and 7809 High-level Data Link Control (HDLC) and uses terminology found in these documents. It also follows the principles of Consultative Committee in International Telegraph and Telephone (CCITT) Recommendation Q.920 and Q.921 (LAP-D) in the use of multiple links, distinguished by the address field, on a single shared channel. Parameter negotiation was extracted from ISO IS 8885. The data-link service definitions were extracted from ISO IS 8886." > I was referring to digipeating with respect to routing. Routing > messages is the big problem with a ham network because the > connectivity is totally dynamic and the issues with hams changing > locations. Overall routing is a layer 3 protocol problem. Well, if packet radio is in the sad status it is nowadays, it would be even harder, if not impossible, to add such capabilities just by the hams effort. It does not seem realistic to me now. > Your perspective on the use of AX.25 hardware probably differs from > mine. There is little of it in use in the US except for Winlink 2000 > VHF/UHF links. Providing gateways and bridges to existing networks is > problem to address. We certainly have different perspectives. For me, HF was the way to achieve BBS connectivity and forwarding at large distances. HF forwarding has lost critical mass, and I doubt if it will ever recover it without a sound improvement. Whatever the causes may be, the BBS forwarding network is virtually inexistent, all has gone to WL2K and that is only for email style exchanges, using hard to get controller boxes, and far from the style and content of the old BBS network. That was a way of getting news relevant to hams, DXpeditions, operating events and plain ham to ham contact all around the world. It was important to many hams without email and Internet connectivity here. Packet was window to the world, accesible from your own equipment, that did not require fees or permissions other than an appropiate ham license. This situation is still widely prevailing. The possibility of better modems and a change of paradigm back to HF packet radio (or a suitable substitute) gives me a slight hope that some of the large network that once existed might be regained. First things first, I feel that an reconfigurable modem, or at least, a more suitable one is a priority. If a better protocol ever gets developed to substitute AX.25, it could use it. With the protocol in use, or another, we still have the same modem problem standing as a quarter of a century ago. 73, Jose, CO2JA
