Digital Networks

The Digital Domain of Amateur Radio - Wireless TCP/IP - Amateur Radio Digital Communications (NET-AMPRNET) AMPRNET


One of the oldest digital networks makes a come back, this time using more robust natively IP capable radios.


The AMPRNet (AMateur Packet Radio Network) is a name used by amateur radio operators for computer networks connected over amateur radio.  The AMPRNet is connected by wireless links and Internet tunnels. Due to the bandwidth limitations of the radio spectrum, VHF and UHF links are commonly 1200 baud, and usually restricted to a maximum of 9600 baud. 300 baud is normally used on HF. Microwave links generally do not use conventional packet radio, and instead use the commercial Wi-Fi access points (HSMM). The AMPRNet fully supports TCP/IP allowing for support of all network protocols.

Many hams are unaware that a Class A IP address block  (16.7 Million IP addresses)  has been set aside for amateur radio users worldwide to use for connecting their radio equipment to and though the internet.

This address allocation was originally obtained in the late 1970's by Dr. Hank Magnuski (KA6M) long before the public internet was in it’s infancy.  

At the time the internet was called ARPA (Advanced Research Projects Agency) Net later renamed The Defense Advanced Research Projects Agency (or DARPA).  

It wasn't till about 1973 development began on the protocol later to be called TCP/IP, it was developed by a group headed by Vinton Cerf.  The TCP/IP protocols were adopted as Military Standards (MIL STD) in 1983, and all hosts connected to the network were required to convert to the new protocols.  But the public Internet didn't really emerge till the 1990's.

Back 1969, Norman Abramson launched Aloha Project at University of Hawaii.  Motivated by the poor telephone lines in the Hawaiian Islands, funded by ARPA to investigate how to build a packet switched network based on fixed site radio links.  At the University of Hawaii it was not really an option to use the PSTN or any form of cabling between Hawaii’s many islands. It opted instead to connect the seven colleges spread across four islands by the use of amateur radio.  Norm performed a number of experiments around 1970 to develop methods to arbitrate access to a shared radio channel by network nodes. This system operated on UHF frequencies at 9600 baud.   Abramson later developed a satellite version of ALOHAnet called PACNET.

Internet Pioneer Paul Baran, W3KAS an engineer who helped create the technical underpinnings for the Arpanet, the government-sponsored precursor to today’s Internet.  In the early and mid 60's he came up with the concepts of packet switching and distributed networks.  He also proposed a decentralized network, a way to create a survivable infrastructure.  This is where radio links came into the picture. 

Baran subsequently founded a slew of technology companies including Packet Technologies and Metricom, and still continued to be actively involved in founding new start-ups – the most recent being Ethernet over wireline outfit Plaster Networks, and the IP TV infrastructure company GoBackTV.

Amateurs all over the world have been networking wirelessly, and have been long before "Wireless Web" became a cell phone feature.  Volunteer hobbyist ham radio operators are investigating the construction of an entirely radio-based world-wide network using TCP/IP.  Hams are in an unusual situation compared to the rest of the Internet. We're trying to build our own radio-based network, so for the goals of the network, radio connectivity is more important than internet connectivity. 

Sadly, when the Internet became part of everyday life, the amateur packet radio networks that had flourished in the 1980s and early '90s declined sharply. (The most popular application of AX25 packet radio today is the Automatic Position Reporting System, or APRS.)

The effect of the Internet on packet radio was devastating. Unlike amateur packet radio, the Internet was extremely fast, reliable over long distances and capable of easily handling large file transfers. The allure of "instant" global e-mail was too great for most packet users to resist.

Amateurs abandoned traditional packet radio in droves, which resulted in the shrinkage or collapse of amateur networks throughout the world. (The effect was similar to the impact cellular telephones had on amateur repeater autopatch systems. Once everyone had an affordable and private wireless telephone , the practice of making a call through an autopatch was rendered obsolete.)

Looking back:

Around 1978, group of amateur radio operators, the Vancouver Amateur Digital Communication Group (VADCG) in British Columbia, Canada began experimenting with Packet radio using a Terminal node controller (TNC) developed by Doug Lockhart, VE7APU.  Federal Communications Commission approved the transmission of ASCII for Amateur radio in the United States in 1980, and AX.25 was born.  It was considered standardized in 1984 with the release of the v2.0 specification.

Use of the TCP/IP over radio dates back to even the DOS days, using a TSR (terminate and stay resident) application to handle the TCP/IP traffic, and command line utilities to handle ping, ftp transfers, and more. In 1985, Phil Karn, KA9Q developed and made public this TCP/IP stack software for MS-DOS know as NOS.  When Linux came along also in the 90's, shortly there after this became the first and only operating system to include amateur radio AX.25 protocol support built-in.  Allowing direct TCP/IP over amateur radio too.

Part of the reason the majority of amateur packet radio networks during the 1980's and 90's never grew past 1200 baud us due to the availability of radios and their architecture.

1200 baud signals for transmission are created using audio frequency shift keying. These can be fed directly into the microphone input of everyday voice transceivers.

Pure frequency shift keying is used for 9600 baud packet and this signal must be applied to dedicated 9600 baud ports on the transceiver. (The 9600 baud port didn't start to be a standard on radio's till the mid to late 1990's.)

The various ham bands also have restrictions on authorized bandwidths and symbol rates for data emissions:

20 kHz, and 19.6 kilobauds on 2 meters.  100 kHz, and 56 kilobauds on 70 cm.  Above 900 MHz, there are no authorized bandwidth or symbol rate restrictions.

It should be noted that using more advanced emissions such as spread spectrum then these limits do not apply.

When 802.11 devices came to the consumer market, amateurs started to realize the range of these can be extended with high gain outdoor antennas. While still somewhat distance limited, they realized these could be further extended by adding Mesh networking layer.

It flourished into a great way to build backup high speed networks on the cheap. These networks have the potential to draw new blood to the hobby.

HSMM seems to stem from a ARRL HSMM working group from a number of years ago.  Despite that group falling apart, independently amateurs all over the place have embraced
the technology.  As interest in voice repeaters continues to wane, multi-media networks do make perfect sense.  These more modern types of networks have the potential to draw new blood into the hobby.  New hams who have software skills that can help the community with software defined radio and so forth.  

These types of networks are long over due, and its good they are continuing to grow.  It helps ham radio stay relevant.  And ham radio provides a platform for those who want to learn about wireless technology by experimenting.

Why HSMM ?

Use it or Lose it

First and foremost it can put our microwave frequency allocations to good use.   These allocations (23cm-300GHz) make up 99% of hams total available frequency allocations. Yet, it's estimated that only 1% of hams are involved with any microwave operations.  

Of the above, over 99% of hams use a tiny fraction (0.3%) of the total ham frequency allocations while the remainder of our available ham allocation is essentially ignored. By the way, ARRL said that as of April 2010, there were about 688,500 personal ham radio licenses in the USA. If only one percent of these were microwave users, that would be 6885 hams. We often hear that the majority of licensed hams are inactive. How many microwave experimenters do you know?

About 40 years ago 2 meters and 70 cm were basically uncharted areas. Now they are populated. Undoubtedly the future of ham radio is in our huge - virtually unused microwave allocations. They have the necessary bandspace to support wideband modes capable of multi-media transport.

Nearest I can determine, the last time ARRL bandplans were reviewed was nearly 20 years ago for 50 MHz and above.

The FCC Uses & Capabilities of ARS Report to Congress was released August 20, 2012 (DA 12-1342).

Under "Other impediments"  (page 12) item 36 in the FCC report, they do acknowledge that:

36. Some commenters identified Commission rules that they believe impede advanced amateur communications. The ARRL asserts that the Commission’s regulation of emission types and digital bit rates is overly conservative and can prevent amateur operators from using the emission type and frequency suitable for transmission path and the information to be transmitted.

It's also worth mentioning that in some of the comments of Scot Stone Deputy Chief, Mobility Division of the FCC's in DA 08-1082 state:

We also believe that imposing a maximum bandwidth limitation on data emissions would result in a loss of flexibility to develop and improve technologies as licensees’ operating interests change, new technologies are incorporated, and frequency bands are reallocated. Additionally, we believe that amending the amateur service rules to limit the ability of amateur stations to experiment with various communications technologies or otherwise impeding their ability to advance the radio art would be inconsistent with the definition and purpose of the amateur service. Moreover, we do not believe that changing the rules to prohibit a communications technology currently in use is in the public interest.

There have been prior efforts to overhaul the bandwidth rules.

Back in 1977, the FCC issued a NPRM, Docket 20777 suggesting a change from emissions authorization to bandwidth authorization.  And in November 2005, the ARRL formally asked the FCC to adopt the League's plan to segment the Amateur Radio bands solely by emission bandwidth rather than by mode (RM-11306).  In both cases, widespread misconceptions led to withdrawals of the proposals.

The commission in 1978 reluctantly relented and decided no to adopt the proposal, stating that; “the comments indicated that for the sizable portion of the amateur community who do not experiment, the present emissions table is preferable. Accordingly, the Commission will not adopt the proposed maximum bandwidth table.” [FCC Release No. 78-588]

Powerful Transport Flexibility

High Speed Multi Media data links can support most of the traffic that the Internet currently does, including; remote printing and facsimile, video conferencing & instant messaging, voice, the Web (HTTP), file transfer (FTP), and forums.   D-Star Digital voice and data, Voice Over IP using SIP & Asterisk private branch exchange (PBX) open source telephony switching technology's well as Electronic Mail even via WinLink, AX.25 and more, can all be supported over a High Speed Multi Media network.  Talk about flexibility!

The concept is nothing new.  In 1989 Glenn, N6GN first described an inexpensive 2-Mbit/s microwave data link,  to build an amateur radio network capable of variety of applications, enabling amateurs to share resources. "Remote digital control of repeaters or even complete stations, including audio or video uplinks and downlinks, can be supported. Conventional voice repeaters (analog) may be replaced by digital hardware for completely digital round tables. Since this data can be transmitted anywhere the network permits..."  

In 1997 TAPR, the group that developed the original TNC, began development of a 1 watt, 128 Kbps 900 MHz FHSS radio, suggesting this is the future for amateur packet radio.

A decade after Glenn's work and after the internet became mainstream, John, KE5FX detailed an Experimental Microwave Data Link for 10-Megabit Ethernet based on Glenn's work.  John, noted that "little progress has been made towards realizing the benefits of high-speed data networking in the Amateur Radio realm" and documented his work  "to help bring Amateur Radio into the twenty-first century."  

Internet Threats and Regulation

Some 10-20 years ago there were many private networks for automated teller machines, telephone, merchant credit card verification and so forth.  Now most of this all happens over the internet.  If there were some sort of major internet outage or attack, many day-to-day things would be interrupted.

At the same time many ham radio systems use the internet for wormhole-like connectivity.  APRS, WinLink, D-Star, IRLP, Echolink and so forth.  An emphasis on building our own backbone and infrastructure is just simply not there.  This leaves vulnerabilities in our emergency communications reliability.

There are some unknown vulnerabilities in the upcoming switch to IPV6, such as distributed denial of service attacks on IPv4 to IPv6 gateways.  As well as root nameservers, and core internet routing.  

2008 YouTube Hijacking: Pakistan Telecom (AS17557) started an unauthorized announcement of the prefix

April 2010 - China Hijack: a Chinese Internet provider (AS23724) announced 40,000 routes belonging to other ISPs / enterprises around the world

In January 2011 due to protests in Egypt, the Egyptian government ordered service providers to shut down all international connections to the Internet.  Which showed to have a crippling effect on a modernizing economy. 

Simultaneously, the United States is debating a bill to create an Internet kill switch, also known as the PCNAA bill.  In conjunction with this there was a bill (H.R. 607 Broadband for First Responders Act of 2011) that posed a threat to the lower part of the 70 cm band.  The proposal was that the Dept. of Homeland Security was going to in-effect build a 400 MHz WiFi network, for if the switch was ever thrown.

Fortunately, Bill HR 607 looks defeated.  But obviously if we as amateurs could do this, it would be an asset (in the event of), and at no cost to the taxpayer, unlike the Dept of Homeland Securities proposed implementation.

Another thing to point out is that the government is hiring "hackers" (reportedly 1,500 of them), probably because many predict the internet will be the target of future terrorist activities, and wars will be fought over it.  And in 2011, White  House Cybersecurity Coordinator Howard A. Schmidt (W7HAS), states, "The White House is looking for ways that the great work of Amateur Radio operators can continue to support emergencies in the future with particular attention to increased use and dependency on internet based technologies."

In 2010 it appeared Net Neutrality was adopted after years of debate.  In short order Verizon appealed and it was decided in federal court that broadband is currently classified by the FCC as an information service, a category that gives the agency a fairly limited set of regulatory options. If Internet providers were classified instead as common carriers, the FCC's rule would likely stand.  Faced with this dilemma, the FCC may in 2014 either choose to argue that its regulations do not fall under the rubric of common carriage, or attempt to reclassify broadband as a common carrier,

In 2013 CryptoLocker a ransomware trojan first surfaced.  

For true redundancy, a non-critical network can and should be built by the amateur service to avoid this single point of failure.

I know it sounds crazy, since many of us still do very little on-line checking and that sort of thing. But if you can take down the internet, or majorly cripple it, online stock trading and banking transactions are all transported over the internet, as well as a large portion of phone calls. That would have a major impact on the economy. I encourage you to take a moment and read up on the Egypt thing that happened a while back.

Ham radio used to be a good starting place for many who later entered broadcast and electronics careers.  Today those positions are few and far between due to disposable electronics and consolidation of engineers with mega broadcast groups.  What is the most notable/abundant "tech" career today is IT (information technology) work.    Building these networking helps ham radio stay relevant.  These networks have the potential to draw new blood into the hobby.  New hams who have software skills that can help the community with software defined radio and so forth.

The Need for Speed and Digital Networks

Nearly 10 years ago a survey conducted by the ARRL Technology Task Force, of League members and other amateurs revealed that the number one interest in new technologies was in high-speed digital networks.  Amateur radio, particularly EmComm (this was just after 911), needed some means of data transmission significantly faster than conventional packet radio.  

Winlink is severely limited in capabilities and doesn't necessarily even conform to Internet Engineering Task Force (IETF) standards.

John Champa, K8OCL was the chairman of the ARRL High Speed Multi-Media working group that ran from 2001-2007.  John and his group showed ham radio operators that consumer off-the-shelf 802.11 hardware could be used under Part 97.

All the various regional HSMM groups popping up all over seems to stem from the ARRL HSMM working group from a number of years ago.  Despite that group falling apart, independently amateurs all over the place have embraced the technology.  It's great in my opinion.  As interest in voice repeaters continues to wane, multi-media networks do make perfect sense.  These more modern types of networks have the potential to draw new blood into the hobby.  New hams who have software skills that can help the community with software defined radio and so forth.

Outside ham radio, as consumers were now live in a world where to keep thing interesting and new we have a flexible application space.  Be that apps on our phones, software on our PCs, and even firmware updates to our more hardware like devices.

That has been notable absent in ham radio.  I.e. What it is when you buy it, is what it will be 5 years from now unless you want to totally replace it for the tune of several hundred dollars.

Ham radio used to be a good starting place for many who later entered broadcast and electronics careers.  Today those positions are few and far between due to disposable electronics and consolidation of engineers with mega broadcast groups.  What is the most notable/abundant "tech" career today is IT (information technology) work.

Ironically today wireless is all around us as consumers.  3 and 4G, bluetooth, proximity sensors etc.

In my humble and simple opinion: These types of networks are long over due, and I am glad they are continuing to grow.  It helps ham radio stay relevant.  And ham radio provides a platform for those who want to learn about wireless technology by experimenting.

Bill Pasternak, WA6ITF writes that the ham using a developing HSMM "are truly forward looking hams was that they have likely developed the hardware and software that in this writers opinion will eventually replace the FM (and all digital voice/data relay modes) repeaters as the backbone of ham radio utility communications.

If noting else, the concepts of a self-discovering and self healing network totally eliminate the need for any form of coordination committees and the like and in doing so also remove much of the politics associated with repeaters."

The Future:

And it doesn't have to be limited to just slower packet radio for TCP/IP, either. Some of the newer 802.11 wireless ethernet devices use frequencies that meet with amateur radio spectrum in the 2.4 GHz area. As a result, amateurs can modify the Part 15 compliant devices to increase the power and use better antennas, providing more gain and increasing usable range. These devices are considerably faster at up to 54 megabits per second than the 1200 and 9600 bit per second speeds of VHF and UHF packet radio.

Good connectivity enables a number of applications that were not previously practical to experiment with due to bandwidth requirements; among these could be digital voice repeater linking, digital quality facsimile picture transmission, television (D-ATV), Web-SDR, multimedia, and so on.

Since the mid 1980's the 44/8 allocation has been administered by Brian Kantor, WB6CYT. He also manages the low-bandwidth tunneling  44/8 router, (routing between various 44.x.x.x networks are typically done by IPIP encapsulation where true amateur routes do not exist).  This router allows a minimal connectivity between the main Internet and some parts of the AMPRNet through gateways. It is there primarily to allow experimenters on the AMPRNet the opportunity to exchange information and to obtain access to Internet resources.  Each of the gateway entities in the UCSD router determine to some extent, what is done at lower levels. Some areas subnet while others do not. 

In early 2012, Heikki Hannikainen, OH7LZB (the ham behind modernized the amprnet routing by writing a custom RIPv2 daemon to receive RIP updates from the 44/8 routing service, and insert them in the Linux routing table.  This has replaced the encap.txt and munge script method.  In late 2012 a new unified interface was given to  

Along with the new interface, came policies and an Acceptable Use Agreement. 

This allows those with the capability to enable directly routed subnets via BGP advertisement.  This will help shed the load on UCSD, and reduce a single point of failure.

All of the BGP announcements on the internet that include 44 space can be determined by looking at the ARIN Allocated Address Table at: current/data-add-ARIN

Prior (1995-2012); another email robot that Jim Fuller, N7VR maintained emailed a daily encap.txt list of NOS style route commands.  From there if you were on the ball you had a cron script munge these into your gateways routing tables. Most folks who ran gateways were not on the ball and would manually install route updates as time permitted.

And before that Warren Toomey VK1XWT, ran the gateways robot.

IPIP can not traverse NAT because first of all it uses proto 4 (encap) and not TCP or UDP, so contrack, which manages NAT traversal does not support it.

In a NAT situation, incoming connections not triggered from the inside don't get translated, since the NAT doesn't know the originator. Being a stateless point to multipoint communication, you do not have a "inside" originated connection for all connections. It is expected that NAT knows where to forward a data packet by using information from the original outgoing connection (established and related packets are sent to the internal originating ip ), which is not the case for IPIP since incoming data from another host (we have a mesh architecture) has no corresponding outgoing connection.

On the other hand, in OpenVPN, if the server is located outside, all connections are stateful and trackable by contrack, being a single IP endpoint on port 1194 originated inside, so NAT traversal is as simple as any connection originated locally.

Part of the reason Amprnet uses IPIP tunnels instead of something like openvpn has to do with keep alive traffic and decentralization.  The other reason is the RFC for IP Encapsulation within IP dates back to the 1980's when the Amprnet got started.

Openvpn and other more modern protocols all have IP tunneling as part of their ability to connect disjointed network segments and hosts.  However they all use a stateful client to server approach.   This is so that the server can maintain a return path though any potential NAT and firewalled paths.  The keep-alive traffic from this periodic handshaking would add up to a rather large amount for a class A network, such as 44 net, even with say just 200 tunnel points.

With IPIP, decentralized peer to peer tunnels are used, which saves a very large amount of bandwidth that would otherwise be necessary when everyone goes though a central server.  Also with IPIP, you don't have that single point of failure.  This mesh method has been used since the Amprnet's inception.

IPv4 Network 44/8 is known as the AMPRNet, named from "AMateur Packet Radio Network".  Much of the AMPRnet piggy-backs over the internet very much like a VPN (Virtual Private Network) except the amateur lines are not private. This greatly improves the long-haul traffic handling and it is just the "last mile" that is the bottleneck in the system, that 10 miles or so to your radio location..  The current structure of the AMPRNet is that there are a bunch of fully- and partially-isolated ("disjoint") subnets in nearly every country and most major cities around the world.  In most countries, there is a local coordinator who is responsible for assigning an address and updating the master hosts list.

Just as 20 years ago, the AMPRNet has served as a coordinated approach to connect disjointed subnets by the way of tunnels, it serves that same core utility as amateurs attempt to build these higher speed networks.  The difference today is, nearly all applications speak IP natively.  In recent years, various other network-based amateur systems have developed, including EchoLink, IRLP, D-Star, WinLink, etc. 

Most if not all of these internet connected amateur systems require network address translation, port forwarding, dynamic host registration, and some method of amateur authentication.  The NAT and port forwarding is because a shortage of public IP addresses.   DNS is needed to bind the public IP to an amateur callsign or station running  these services.  Authentication is a regulatory one.    

The amprnet can/could provide a solution for all of this, rather than each internet connected amateur system having to create their own solutions.  

Related: - Providing authenticated amateur radio services on the Internet - OH7LZB

A number of social networking privacy issues have arisen on the public internet.  In the amateur arena, the popular callsign lookup site, closed detailed lookup results to logged in members in late 2012.   Most of what we as ham post on the public internet is not of interest to the general public, and need not be public.  

For hams into coding software (an area to grow), there are a number of public code repositories.  Issues with public repositories arrive in terms of possible copyright violations 

Reasons to create our own private interconnected place:

QSL cards with automatically flagged copyrighted image

Unnecessarily exposing developmental code security to the general public.  (we have security by only sharing amongst ourselves)

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