HF Multicast

STANAG 5066 provides a non-ARQ service which provides unreliable data transfer that can be used with STANAG 5066 multicast and broadcast addresses. STANAG 5066 networks define a default broadcast address and allow configuration of custom multicast addresses. For most scenarios, it is sensible to use the broadcast address, as there is no possibility of sharing the channel. Basic use of broadcast/multicast is inherently unreliable. The STANAG 5066 non-ARQ allows the requester to specify the number of retransmissions, which gives a mechanism to increase reliability. ACP 142 is a generic, reliable multicast protocol. STANAG 5066 Annex Q specifies the operation of ACP 142 over STANAG 5066, in particular to support SMTP email and STANAG 4406 military messaging. This is an example of sophisticated use of STANAG 5066 multicast. HF Operator Chat, specified in STANAG 5066 Annex O, provides a simple chat service operating directly over STANAG 5066, which includes the option to broadcast a message to all nodes on an HF network and utilise multicast. It is a good example of simple, direct use of HF broadcast and multicast.