AMPRNet: The Amateur Packet Radio Network

Introduction to Packet Radio and TCP/IP

Packet radio is a fundamental medium for point-to-point communications in the amateur radio community. However, building a comprehensive network where stations can communicate regardless of direct contact requires additional layers of mechanisms. This is where TCP/IP protocols come into play. Originally developed from research into reliable military communications, TCP/IP has proven to be robust and efficient, as demonstrated by its widespread use in today’s Internet.

The Advent of TCP/IP in Amateur Radio

Innovative amateur radio enthusiasts have adopted TCP/IP protocols for digital communications within the amateur radio community. This adoption leverages the numerous advantages of TCP/IP while also fostering enhancements to the protocols, arising from unique challenges encountered when transmitting over radio links. Many recent improvements to TCP/IP originated from amateurs striving for reliable and efficient data transmission over lossy and congested radio paths.

What is AMPRNet?

The Amateur Packet Radio Network, known as AMPRNet, utilizes the IPv4 Network 44/8. This network, allocated in the 1970s by Hank Magnuski, is administered by a distributed group of regional coordinators. These coordinators assign addresses to amateur radio operators within their regions, contributing to the construction of an entirely radio-based worldwide network using TCP/IP.

Network Structure and Management

AMPRNet is a network of disjoint subnets managed by volunteer hobbyist amateur radio operators. These subnets, spread across nearly every country and major city, vary in connectivity. Some have radio links to adjacent subnets, while others are isolated or connected via Internet tunnels. The network’s structure is dynamic, with the status of subnets changing daily.

A low-bandwidth tunneling router at the University of California, San Diego, managed by Brian Kantor, provides minimal connectivity between the main Internet and parts of AMPRNet. This connectivity is primarily for experimenters to exchange information and access Internet resources. However, AMPRNet is not intended to replace traditional Internet services and remains an experimental network.

AMPR.ORG: The Domain for Amateur Radio Digital Communications

The AMPR.ORG domain is available for amateur radio operators to register their AMPRNet hosts and other related computer systems. Domain names in AMPR.ORG are accessible to any licensed amateur radio operator interested in advancing digital communications. Local coordinators assign addresses and update the master hosts list, with many Indonesian amateurs participating under the guidance of national coordinator Onno W. Purbo, YC1DAV.

Connectivity and Usage Considerations

Most AMPRNet hosts are not connected to the Internet. The network consists of thousands of computer systems registered in the AMPR.ORG domain, but few can reach or be reached from the Internet. Additionally, amateur radio stations must adhere to strict content restrictions to avoid government fines or forfeiture of their licenses and equipment. Therefore, amateurs are cautious about the content transmitted over their equipment.

To check a host’s Internet connectivity, standard Internet tools such as traceroute, ping, dig, nslookup, and smtp VRFY can be used. AMPR hostnames typically include the amateur radio callsign, making it easy to identify and locate the station.

The Evolution and Role of AMPRNet

Since its inception in 1981, AMPRNet has played a significant role in amateur radio digital communications. The network provides a platform for packet radio and digital communications between computer networks managed by amateur radio operators. In 2001, parts of the IPv4 range were repurposed for network telescoping, recording events like the spread of the Code Red II worm. Due to IPv4 address exhaustion, portions of the range were sold for conventional use in mid-2019.

Conclusion

AMPRNet represents a unique and evolving experiment in amateur radio digital communications. While it is not a substitute for commercial Internet services, it offers a valuable platform for hobbyists to explore and enhance TCP/IP protocols over radio links. Through the efforts of dedicated volunteers, AMPRNet continues to advance the art of amateur radio, fostering innovation and connectivity in the global amateur radio community.