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.
Packet radio is a ghost of what it once was on VHF. Some areas apparently have some surviving networks in high population areas, but I don't know how much use they actually get compared to the "old days" when the main problem was congestion with too much traffic for the narrow pipe, even with an extensive network throughout our state with higher speed 9k6 links connected to node stacks. Today there are a number of nodes on the 144.390 APRS frequency running at 1200 baud. There are a handful of Winlink 2000 VHF nodes, however they are often concentrated in the larger cities and are not easily accessed outside of those areas. In order for a VHF packet type of system to ever be rebuilt, it would need some extremely compelling reason(s) and I question whether that is possible due to the ubiquitousness of the internet and expanding commercial wireless availability. The one exception has been the reintroduction in some areas for emergency networks. On the HF side, packet never worked well enough to have a serious use except (perhaps) when the sunspots permitted the upper HF bands to handle longer distance traffic on more stable near MUF paths. We have a group on on 80 meters in my state that has some kind of BBS system set up. When I have attempted to monitor during daytime hours, I mostly see retry after retry so I don't know how much traffic is getting through. At night, such a network would be completely unusable. Before any effort is made to improve on the existing protocol and structure, wouldn't it be wise to determine just what is the purpose of such a network? I don't see any interest from hams in my area in further development of VHF networks for general use. They have the APRS system in place which seems satisfactory for the very small minority of hams who use such systems. Similarly, the HF part of the Winlink 2000 system is available for casual ham travelers who want "free" access to the internet and especially those who are willing to support the SCS modem for those areas without VHF connectivity. From my perspective, the main potential in both VHF and HF digital networking may be public service/emergency use. For close stations, VHF packet can work quite well and could be digipeated by ad hoc placement to get traffic through. From practical experience, we did this two decades ago with a FEMA nuclear incident exercise, but this is no longer possible on VHF due to the loss of the networks. And such longer distance packet VHF networks are extremely fragile and risky for actual emergency conditions. You never know where you need to have connectivity for public service, until you are involved in it. That is why having the ad hoc capability to employ a BBS structure, e-mail structure, and near real time direct connections are so important. Those needs are not being met by any current amateur radio system, but might be possible with newer technology. What other networking solutions do you see being unmet that a new paradigm would solve? 73, Rick, KV9U 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. > 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". 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. > > 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 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. > > 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. > > > > >
