STANAG 5066

Overview

The NATO standard STANAG 5066, Profile for High Frequency (HF) Radio Data Communication, defines a layered suite of protocols for data communication over beyond-line-of-sight HF radio.

Status

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 It has since been superseded by Edition 3, ratified in December 2010. STANAG 5066 Edition 4 is in preparation with the current version, which is “Draft Version 1.6” published on 27 August 2021. Note that with the release of Edition 4, the title of the specification was also changed.

Change of title of the STANAG 5066 specification:

Editions 1, 2 and 3: Profile for High Frequency (HF) Radio Data Communication
Edition 4: Technical Standards for HF Radio Link Layer and Applications Support Protocols

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 known as Edition 2) adds a mechanism called 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. RapidM products that support Edition 3 are the RC66 and RC8 products.
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 and D Appendix D) and ALE protocols (standard MIL-STD-188-141D Appendix G, 4G ALE/WALE).

Relevance

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.
RapidM have product implementations and experiences for both STANAG 5066 Edition 3 and Edition 4:
- Edition 3 should be considered for legacy (narrowband) deployments.
- Edition 4 should be used for new (narrowband and wideband) deployments.

STANAG 5066 Protocol Stack and Clients

The STANAG 5066 Edition 4 specification has undergone several changes when compared to the previous editions. The table below provides a summary of Edition 3 and Edition 4 Annexes.

Ann.	S5066 Protocol Stack and Clients Description	Ed. 3	Ed. 4	Notes
A	Subnetwork Interface Sublayer	✔	✔
B	Channel Access Sublayer	✔	✔
C	Data Transfer Sublayer	✔	✔
D	Interface between Data Transfer Sublayer and Communications Equipment	✔	✔
E	HF Modem Remote Control Interface	✔	✔
F	HF Subnetwork Client Requirements	✔	✔
F.1	Standardised Client Requirements	✔	✔
F.2	Subnet Management Client (Optional)	✔	✔
F.3	Character-Oriented Serial Stream (COSS) Client (Optional)	✔	✔	See Annex P in Ed. 4
F.4	STANAG 4406 Annex E: Tactical Military Message Handling (T-MMHS) Client (Optional)	✔	✔	See Annex Q in Ed. 4
F.5	STANAG 5066 HF Mail Transfer Protocol (HMTP) Client (Optional)	✔		Not in Ed. 4
F.6	HF Post-Office Protocol (HFPOP) Client (Optional)	✔		Not in Ed. 4
F.7	Operator Order Wire (HFCHAT)) Client (Optional)	✔	✔	See Annex O in Ed. 4
F.8	Reliable Connection-Oriented Protocol (RCOP) (Optional)	✔		Not in Ed. 4
F.9	Unreliable Datagram-Oriented Protocol (UDOP) (Optional)	✔		Not in Ed. 4
F.10	Extended Client Definition Using RCOP/UDOP Appl. Identifiers	✔		Not in Ed. 4
F.11	ETHER Client (Optional)	✔		Not in Ed. 4
F.12	IP Client	✔	✔	See Annex U in Ed. 4
F.13	Reserved Service Access Point Identifiers (Optional)	✔		Not in Ed. 4
F.14	Compressed File Transport Protocol (CFTP) Client	✔	✔	See Annex V in Ed. 4
F.15	Unassigned Service Access Point Identifiers	✔		Not in Ed. 4
F.16	RAW SIS Socket Server	✔	✔
G	Use of Waveforms at Data Rates Above 2400 bps	✔	✔
H	Implementation Guide and Notes	✔	✔
I	Messages and Procedures for Frequency Change	✔	✔
J	General Requirements for Enhanced Media-Access-Control (MAC) Capabilities in Multi-Node STANAG 5066 Networks	✔	✔
K	High-Frequency Carrier-Sense Multiple-Access (CSMA) Protocols	✔	✔
L	High-Frequency Wireless Token-Ring-Protocol (WTRP) Requirements	✔	✔	Ed. 4 is Not Interoperable with Ed. 3
M	Adaptive Time-Division Multiple-Access (ATDMA) Protocols using STANAG 5066 DTS Layer Messaging	✔	✔	No Information in Standard
N	Guidance on Address Management in STANAG 5066 Networks	✔	✔	Information Only
O	HF Operator Chat		✔	New to Ed. 4
P	ACP 127 and Character-Oriented Serial Stream		✔	New to Ed. 4
Q	ACP 142		✔	New to Ed. 4
R	Routing Sublayer		✔	New to Ed. 4
S	SIS Access Protocol		✔	New to Ed. 4
T	STANAG 5066 TRANSEC Crypto Sublayer Using AES and Other Protocols (Requires Export Permit*)		✔	New to Ed. 4
U	IP Client		✔	New to Ed. 4
V	Compressed File Transfer Protocol		✔	New to Ed. 4

Table 1: STANAG 5066 Editions 3 and 4 Comparison

Figure 1: STANAG 5066 Editions 3 and 4 Illustrated

STANAG 5066 Services (Standard)
Serial Messaging (ACP-127/COSS)	The COSS Client provides a simple messaging service for bandwidth-constrained networks. Suitable for ARQ and broadcast networks. The COSS Client is included in BRASS/BRE1TA and is widely deployed. COSS is retained in STANAG 5066 Edition 4.
Operator Chat (HF Chat)	Provides a very basic messaging service that can be used for informal point-to-point or broadcast communications. HF Chat requires minimal configuration and does not rely on additional software. This is an optional component.
Internet Chat (XMPP PEP, IP Client)	Future Service.
Push Email (CFTP and HMTP)	The CFTP and HMTP clients provide push email functionality over HF, which is required for BRASS / BRE1TA. The HMTP and CFTP clients are widely deployed. The CFTP Client supports compression and can optimise email transfer significantly. The HMTP Client does not use compression, and therefore supports “Delivery with Errors”, which allows partially received emails to still be passed on to the client. The Push Email service can be used to send emails either directly to the intended recipient or a central HF POP server.
Pull Email (HF POP)	Pull Email relies on a central server to host emails for the network. HF POP is typically deployed where it is expected that the network is not fully connected and nodes will not always be able to reach each other directly. Pull email allows clients to selectively download emails when convenient.
UDP/IP Data (HF IP Client)	The UDP service is provided using the HF IP Client, which is a BRE1TA/BRIPES requirement. UDP is a connectionless protocol with minimal overhead. Because of this, UDP applications are typically more prone to work over HF IP. UDP applications can leverage the bulk transfer of S5066, as there is no window that limits the data in any way.
TCP/IP Data (HF IP Client with IP PEP)	The TCP service is provided using the HF IP Client, which is a BRE1TA/BRIPES requirement. The performance of the TCP service is usually not very good over HF due to high latencies. The high latencies also typically limit the amount of queued data. When combined with the RapidM IP PEP, the performance of TCP is similar to that of UDP. The TCP service could be used for various services, including standard SMTP, FTP and HTTP.
STANAG 5066 Services (RapidM Proprietary)
File Transfer (FTP PEP/RCOP)	The RapidM Proprietary FTP service is a proxy for COTS FTP Clients (e.g., FileZilla). The FTP Proxy can optimise the transfer of files using compression, as well as improve the file browsing experience presented to the COTS FTP Client. Future Service.
Web Browsing (HTTP PEP/RCOP)	The RapidM Proprietary Web Browsing Proxy is used with COTS Web Browsers (e.g., Firefox / Chrome). The Web Browsing Proxy optimises the transfer of web traffic by using lossless (e.g., text content), and lossy compression (e.g., reduced quality of images). Furthermore, the number of back and forth transmissions are reduced by fetching expected additional resources before they are requested by the browser. Future Service.