RE: [digitalradio] AX.25 vs Something New
Chuck, No problem. It may just as easily been something I missed. On the SEDSAT Wiki page they describe the sliding window technique used to stream packets. As I recall this was used in the Kermit protocol for PC to PC file transfers. Something similar, modified for half-duplex channels, would be an improvement to our RF digital communications. I liked the point about not needing a timer to monitor timeouts with the sliding window. AX.25 has a plethora of timers that make it a hassle to implement. Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net http://thehamnetwork.net/ -Original Message- From: Chuck Mayfield - AA5J [mailto:[EMAIL PROTECTED] Sent: Saturday, August 09, 2008 7:12 AM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] AX.25 vs Something New Rud, I said It was in the Design http://wiki.seds.org/index.php/SEDSAT-2_Communications_Design_Notes Notes par. 2.2.1. However, I now see that I got off the track and that page applies to Design Notes for the SEDSAT-2. Maybe the par. on fx.25 and the list of possible tnc's are not connected together. If that is the case, then Sorry for the confusion. Chuck
Re: [digitalradio] AX.25 vs Something New
I have not heard of anyone doing this, but it sounds like it could be an improvement. Is anyone on the group experimenting with such proposals? 73, Rick, KV9U Chuck Mayfield - AA5J wrote: Bill Vodall WA7NWP wrote: Phil's paper is from many years ago but the reality is that there was no further movement away from the legacy AX.25 equipment toward a new layer, much less toward a completely new protocol. There is some movement... Check out: FX.25 - Forward Error Correction Extension to AX.25 Link Protocol For Amateur Packet Radio (pdf file 138k) The FX.25 extension to AX.25 implements a Forward Error Correction (FEC) ?wrapper? around a standard AX.25 packet and is designed to supplement the existing AX.25 infrastructure without displacing it. http://www.stensat.org/Docs/FX-25_01_06.pdf http://www.stensat.org/Docs/FX-25_01_06.pdf ... and, perhaps this link http://www.stensat.org/projects/FX-25/FX-25_performance.htm, http://www.stensat.org/projects/FX-25/FX-25_performance.htm but that was in 2006... Chuck AA5J
Re: [digitalradio] AX.25 vs Something New
Several modems on that link claim fx.25 compatibility; TNC-X comes to mind, but they all seem to have been developed for VHF/UHF use, so YMMV on HF. Chuck AA5J Rick W. wrote: I have not heard of anyone doing this, but it sounds like it could be an improvement. Is anyone on the group experimenting with such proposals? 73, Rick, KV9U Chuck Mayfield - AA5J wrote: Bill Vodall WA7NWP wrote: Phil's paper is from many years ago but the reality is that there was no further movement away from the legacy AX.25 equipment toward a new layer, much less toward a completely new protocol. There is some movement... Check out: FX.25 - Forward Error Correction Extension to AX.25 Link Protocol For Amateur Packet Radio (pdf file 138k) The FX.25 extension to AX.25 implements a Forward Error Correction (FEC) ?wrapper? around a standard AX.25 packet and is designed to supplement the existing AX.25 infrastructure without displacing it. http://www.stensat.org/Docs/FX-25_01_06.pdf http://www.stensat.org/Docs/FX-25_01_06.pdf http://www.stensat.org/Docs/FX-25_01_06.pdf http://www.stensat.org/Docs/FX-25_01_06.pdf ... and, perhaps this link http://www.stensat.org/projects/FX-25/FX-25_performance.htm, http://www.stensat.org/projects/FX-25/FX-25_performance.htm, http://www.stensat.org/projects/FX-25/FX-25_performance.htm http://www.stensat.org/projects/FX-25/FX-25_performance.htm but that was in 2006... Chuck AA5J
Re: [digitalradio] AX.25 vs Something New
As I understood in a quick reading, this is aiming at keeping the modem and adding intelligent redundancy, specially for beacons and telemetry. The older equipment just receives some more harmless digital rubbish, and could even receive the same packets with no improvements. Interesting, anyway, because they also report improvements. It has a merit, it keeps compatibility with the deployed equipment base. Also, that they make the improvements in a borderline sublayer, placed on the lower region of layer 2. The effect could be similar to doing it on top of layer 1... But my appreciation is that this still falls short for HF. My idea was not to mess with the protocol, but aim at what I perceive is even weaker, the HF modem. Would a hybrid, FX.25 / more suitable modem combo be worthwhile to investigate? Jose, CO2JA Chuck Mayfield - AA5J wrote: Several modems on that link claim fx.25 compatibility; TNC-X comes to mind, but they all seem to have been developed for VHF/UHF use, so YMMV on HF. Chuck AA5J
RE: [digitalradio] AX.25 vs Something New
Chuck, Would you point me to the claims for fx.25 TNC compatibility? I do not see any specific TNCs mentioned. I am real curious about this because 2 years or so I looked at doing some experiments with modified protocols using existing TNCs. All of them insisted, even in KISS mode, that the received packet be a valid and correct AX.25 packet. I went so far as to check the TNC-X code to see what changes would be needed to allow it to pass invalid packets but decided not to get into PIC development at that time. I like the streaming capability with multiple packets and the FEC code transmitted in one burst. The time delays waiting for TX stability have a big impact on throughput. Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Mayfield - AA5J Sent: Friday, August 08, 2008 3:47 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] AX.25 vs Something New Several modems on that link claim fx.25 compatibility; TNC-X comes to mind, but they all seem to have been developed for VHF/UHF use, so YMMV on HF. Chuck AA5J
Re: [digitalradio] AX.25 vs Something New
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
Re: [digitalradio] AX.25 vs Something New
Phil's paper is from many years ago but the reality is that there was no further movement away from the legacy AX.25 equipment toward a new layer, much less toward a completely new protocol. There is some movement... Check out: FX.25 - Forward Error Correction Extension to AX.25 Link Protocol For Amateur Packet Radio (pdf file 138k) The FX.25 extension to AX.25 implements a Forward Error Correction (FEC) ?wrapper? around a standard AX.25 packet and is designed to supplement the existing AX.25 infrastructure without displacing it. http://www.stensat.org/Docs/FX-25_01_06.pdf
Re: [digitalradio] AX.25 vs Something New
Bill Vodall WA7NWP wrote: Phil's paper is from many years ago but the reality is that there was no further movement away from the legacy AX.25 equipment toward a new layer, much less toward a completely new protocol. There is some movement... Check out: FX.25 - Forward Error Correction Extension to AX.25 Link Protocol For Amateur Packet Radio (pdf file 138k) The FX.25 extension to AX.25 implements a Forward Error Correction (FEC) ?wrapper? around a standard AX.25 packet and is designed to supplement the existing AX.25 infrastructure without displacing it. http://www.stensat.org/Docs/FX-25_01_06.pdf http://www.stensat.org/Docs/FX-25_01_06.pdf ... and, perhaps this link http://www.stensat.org/projects/FX-25/FX-25_performance.htm, http://www.stensat.org/projects/FX-25/FX-25_performance.htm but that was in 2006... Chuck AA5J
Re: [digitalradio] AX.25 vs Something New
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. http://citeseer.ist.psu.edu/cache/papers/cs/2504/http:zSzzSzpeople.qualcomm. comzSzkarnzSzpaperszSznewlinkpaper.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. I recognize him, Rud, but that link is gobbledegook to me. Can you resend it? Chuck AA5J
Re: [digitalradio] AX.25 vs Something New
Rud Merriam wrote: 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 a problem with the formatting on this reflector. Please excuse me for that. My question, as an unenlightened retired engineer, is What difference does it make which model is used if the proposed changes are to Level 1? Apparently I don't speak the same language ...but can the same model(s) not be used with a differing Level 1 protocol? Chuck AA5J
RE: [digitalradio] AX.25 vs Something New
Here is a presentation by Phil with the same information: http://www.qsl.net/n9zia/newlink/page1.html The paper at a different URL: http://www.ka9q.net/papers/newlinkpaper.pdf Phil's papers: http://www.ka9q.net/papers/ Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Mayfield - AA5J Sent: Wednesday, August 06, 2008 10:27 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] AX.25 vs Something New Rud Merriam wrote: I suggest anyone interested in this topic start by reading http://citeseer.ist.psu.edu/cache/papers/cs/2504/http:zSzzSzpeople.qua lcomm. http://citeseer.ist.psu.edu/cache/papers/cs/2504/http:zSzzSzp eople.qualcomm. comzSzkarnzSzpaperszSznewlinkpaper.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. I recognize him, Rud, but that link is gobbledegook to me. Can you resend it? Chuck AA5J Announce your digital presence via our Interactive Sked Page at http://www.obriensweb.com/sked Check our other Yahoo Groups http://groups.yahoo.com/group/dxlist/ http://groups.yahoo.com/group/contesting http://groups.yahoo.com/group/themixwgroup Yahoo! Groups Links
