The NATO standard STANAG 5066, Profile for High Frequency (HF) Radio Data Communications, included in the RapidM RC66, RC8 & RC10 controllers, defines a layered suite of protocols for data communication over beyond line-of-sight HF radio.  Based on RapidM’s field proven and JITC certified S5066 technology, the RC66, RC8 & RC10 controllers in combination with different clients provides reliable data communication services, such as Email, messaging, chat and IP data, over degraded radio networks.


The first edition of the STANAG 5066 – “Profile for High Frequency (HF) Radio Data Communication” was released in April 2000.  It has since been superseded by Edition 3 ratified in December 2010.

Key Features:

  • Edition 1 and Edition 2 are only useful for very small numbers or radios, or where radios transmit for a low percentage of total time, as these versions did not specify any collision avoidance techniques.
  • Edition 3 (until recently know as Edition 2) adds a mechanism call HFRTP (HF Ring Token Protocol) which provides control over which Radio transmits. Edition 3 should be used for most deployments with medium and large numbers of radios.
  • Edition 4 (being finalised) includes the extensions of the protocol stack to be used with the new wideband HF Data Modems (standard MIL-STD-188-110C & D Appendix D) and ALE protocols (standard MIL-STD-188-141D Appendix G, 4G ALE/WALE).


  • The versatility, efficiency, and widespread availability of the STANAG 5066 protocols have led to their use in a large number of Naval and strategic deployments.
  • It supports both ARQ and non-ARQ (Broadcast) and provides network-to-network data communications over HF by creating links and managing data transfer between nodes.

STANAG 5066 Protocol Stack & Clients:

The STANAG 5066 Edition 3 specification consists of the following major annexes, as summarised below:

  • STANAG 5066 Protocol Stack Descriptions:
    • Annex A: Subnetwork Interface Sublayer
    • Annex B: Channel Access Sublayer
    • Annex C: Data Transfer Sublayer
    • Annex D: Interface between Data Transfer Sublayer and Communications Equipment
    • Annex E: HF Modem Remote Control Interface
    • Annex F: HF Subnetwork Client Requirements
    • Annex G: Use of Waveforms at Data Rates Above 2400 bps
    • Annex H: Implementation Guide and Notes
    • Annex I: Messages and Procedures for Frequency Change
    • Annex J: General Requirements for Enhanced Media-Access-Control (MAC) Capabilities in Multi-Node STANAG 5066 Networks
    • Annex K: High-Frequency Carrier-Sense Multiple-Access (CSMA) Protocols (information only)
    • Annex L: High-Frequency Wireless Token-Ring-Protocol (WTRP) Requirements (information only)
    • Annex M: Adaptive Time-Division Multiple-Access (ATDMA) Protocols using STANAG 5066 DTS Layer Messaging (information only; this annex is currently empty, with the title as a placeholder).
    • Annex N: Guidance on Address Management in STANAG 5066 Networks (information only).
  • STANAG 5066 Subnetwork Client Descriptions:
    • Annex F.1: Standardized Client Requirements
    • Annex F.2: Subnet Management Client (Optional)
    • Annex F.3: Character Oriented Serial Stream (COSS) Client (Optional)
    • Annex F.4: STANAG 4406 Annex E – Tactical Military Message Handling (T-MMHS) Client (Optional)
    • Annex F.5: STANAG 5066 HF Mail Transfer Protocol (HMTP) Client (Optional)
    • Annex F.6: HF Post-Office Protocol (HFPOP) Client (Optional)
    • Annex F.7: Operator Orderwire (HFCHAT)) Client (Optional)
    • Annex F.8: Reliable Connection-Oriented Protocol (RCOP) (Optional)
    • Annex F.9: Unreliable Datagram Oriented Protocol (UDOP) (Optional)
    • Annex F.10: Extended Client Definition using RCOP/UDOP Application Identifiers (Optional)
    • Annex F.11: ETHER Client (Optional)
    • Annex F.12: STANAG 5066 IP Client
    • Annex F.13: Reserved Service Access Point Identifiers (Optional)
    • Annex F.14: STANAG 5066 Compressed File Transport Protocol (CFTP) Client (Optional)
    • Annex F.15: Unassigned Service Access Point Identifiers (Optional)
    • Annex F.16: RAW SIS Socket Server

STANAG 5066 Edition 3 illustrated

Figure 1: STANAG 5066 Edition 3 illustrated

RC Family Products Comparison  RC10 RC8 RC66 RC50



Naval & Strategic      
Government & Security  


19″ Rack Mount (Dedicated Hardware)    
PC Software    
Conformance to Standard S5066 Wideband ARQ Stack (Edition 4*)  
S5066 ARQ Stack (Edition 3)        
Annex A – Subnet Interface Layer        
Annex B – Channel Access Layer        
Annex C – Data Transfer Layer        
Annex D – Modem Access        
Annex E – HF Modem Remote Control Interface        
Annex F.3 – S5066 COSS Client (for ACP-127)      
Annex F.5 – S5066 HMTP Email Client  
Annex F.12 – S5066 IP Client      
Annex F.14 – S5066 CFTP Email Client    
Annex F.16 – SIS Protocol        
Annex G: Data Rates Above 2400 bps        
Annex H: Implementation Guide and Notes        
Annex I: Messages/Procedures for Freq. Change        
Annex J: General Requirements for Enhanced MAC ( ) ( )
Annex K: High-Frequency CSMA Protocols        
Annex L: High-Frequency WTRP Requirements ( ) ( )
Annex M: ATDMA Protocols (empty annex) N/A N/A N/A N/A
Annex N: Guidance on Address Management in STANAG 5066 Networks (info only) N/A N/A N/A N/A

Table 1: STANAG 5066 Edition Use, Installation & Conformance to Standard

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