<remark>Make use of SLEP Streaming service, which was not available for 0.1. This provides a better service mapping than direct use of 5066 and provides compression.</remark>
This specification arose from requirements to operate over HF Radio, which has exceedingly high latency (sometimes minutes) low data rates (down to 75 bits/second)
is a widely used HF link level protocol. Direct use of <strong>STANAG 5066</strong> enables elimination of all extraneous end to end handshaking, which is important
to optimize performance. It also enables use of <strong>STANAG 5066</strong> flow control, which is important for resilience.
</p>
<p>
The solution uses the streaming service specified by
</note> - SIS Layer Extension Protocol. <strong>SLEP</strong> specifies three layer services that operate over STANAG 5066, including a streaming service which
provides an equivalent service to TCP. <strong>SLEP</strong> also provides compression, which is mandated for use by this specification.
The solution is based on &xep0361; and requires peer configuration to be established according to <strong>XEP-0361</strong>. The data exchanged between the XMPP servers
follows exactly what is specified in <strong>XEP-0361</strong>. The data is transferred using <strong>SLEP</strong> rather than using TCP.
This specification can be considered as a profile for server to server XMPP communication, to enable XMPP deployment over HF Radio using <strong>STANAG 5066</strong>.
This profile MUST only be used where its use has been pre-agreed and configured for both participating servers.
An example scenario where this protocol is important is where two ships connected by HF Surface Wave communication only need to exchange XMPP messages.
A reliable link (Soft Link) can be established using <strong>STANAG 5066</strong> and XMPP communicated efficiently and reliably over <strong>SLEP</strong>.
Because of potentially very low bandwidth sending server MAY perform traffic optimisation, such as selective removal of stanzas that are not adding sufficient value, like CSNs, or strip selected elements such as xhtml-im.
</p>
<p>
Applications sending data over <strong>STANAG 5066</strong> need to be aware of increased delays and any application level timers (e.g., IQ response timers) need to be set accordingly.
&xep0198; MAY be used over <strong>SLEP</strong>. Although reliability of stanza transfer is provided by use of <strong>STANAG 5066</strong> and <strong>SLEP</strong>, use of
Security Considerations of <strong>XEP-0361</strong> apply. <strong>STANAG 5066</strong> will frequently be employed in conjunction with link level crypto devices, which SHOULD be done when appropriate to provide data confidentiality.
<p>This specification uses STANAG 5066 Edition 4 "TECHNICAL STANDARDS FOR HF RADIO
LINK LAYER AND APPLICATION SUPPORT
PROTOCOLS FOR SINGLE CHANNEL
WAVEFORMS" (November 2021). </p>
<p><strong>STANAG 5066</strong> is a NATO UNCLASSIFED (Releasable to the Public) document that may circulated freely. It is available
on <linkurl='https://www.isode.com/documentation/S5066Edition4ratification.pdf'>https://www.isode.com/documentation/S5066Edition4ratification.pdf</link>.</p>