The AMPRNet (AMateur Packet Radio Network) is a name used by amateur radio operators for computer networks connected over amateur radio. Other names for the network include IPv4 Network 44/8 and Network 44. Much of the information here is historical, as packet radio had an exponential decline within the amateur radio hobby over twenty years, and remaining users have switched to the private address space (10/8, 172.16/12, 192.168/16, etc.).
The use of TCP/IP on amateur radio, using packet radio networks, preceded the appearance of the public Internet. The class A 44 netblock of 16.7 Million IP addresses was set aside for amateur radio users worldwide, having been secured in the 1970s by Hank Magnuski, when computer networking was in its infancy. Packet radio was used as a low level protocol for many competing higher level protocols, and TCP/IP users were essentially a minority due to the complexity of the configuration. The low baud rates also inflamed packet node site owners, as they saw the IP protocol as having too high of a protocol overhead. Very few systems operated over HF for this reason. The best solution on 1200 baud VHF networks emerged as TCP/IP over the ROSE protocol, just before the public Internet made them obsolete. The ROSE system today is maintained by the Open Source FPAC linux project.
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. Although with the advent of mass-produced WiFi equipment on 2.4 GHz and 5 GHz this technology is now being used to provide much faster links on nearby amateur frequencies. 300 baud is normally used on HF. Microwave links generally do not use 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.
The AMPRNet is composed of a series of subnets throughout the world. Portions of the network have point to point radio links to adjacent nodes, while others are completely isolated.
Geographically dispersed radio subnets can be connected using an IP tunnel between sites with Internet connectivity. Many of these sites also have a tunnel to a central router, which routes between the 44/8 network and the rest of the Internet using static tables updated by volunteers.
Recent experimentation has moved beyond these centrally controlled static solutions, to dynamic configurations provided by Peer to Peer VPN.
The Internet protocol (IP) addresses in this block are in the 18.104.22.168/8 network and are available to any licensed amateur radio operator. The assigning of addresses is done by volunteer coordinators. These addresses can be made routable over the Internet if fully coordinated with the volunteer administrators. Radio amateurs wanting to request IP addresses within the 44/8 network should visit the AMPRNet Portal 
44.128.x.x is the testing subnet and consists of 65,536 (216) addresses. Much akin to 10.0.0.0/8, 172.16.0.0/12, 169.254.0.0/16 or 192.168.0.0/16, this is an unroutable private IP block. Connectivity to the rest of the network should be given through router gateways much as one would do with Network address translation in any other private IP block.
- Official site (http://www.ampr.org)
- Amateur Packet Radio Gateways
- AMPRNet Portal
- FPAC Linux software
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