AEDP-4858 resilient file delivery protocol over degraded networks

What it is

AEDP-4858 is a NATO Allied Engineering Documentation Publication: a technical protocol specification, not a management-system or quality-assurance standard. Its own aim clause states it exists "to promote interoperability in air-to-ground file delivery among North Atlantic Treaty Organization (NATO) systems." It does not define a new protocol from scratch; it requires a file transfer system to "comply with CCSDS File Delivery Protocol (CFDP) Recommended Standard CCSDS 727.0-B-5", the civil space-data standard published by the Consultative Committee for Space Data Systems, and adds a small set of NATO-specific requirements on top of it.

Who it reaches and how

The document itself never names a reader role such as supplier, manufacturer or operator. Its requirements fall on "file transfer systems", which it defines as "any system, such as an air vehicle or ground control station, capable of performing file transfers over a data link" - in practice, the engineering teams that build or integrate that function. AEDP-4858 carries no ratification of its own: "the agreement of nations to use this publication is recorded in STANAG 4858". A STANAG binds a nation, not a company directly, so AEDP-4858 reaches a supplier only when a contract or a national authority invokes STANAG 4858 and, through it, this publication. Edition A, version 1 was promulgated in January 2024 and "is effective upon receipt".

What is in scope

The scope is deliberately narrow: "the protocol specified in this document applies to air-to-ground file transfers", and air-to-air transfer is named and excluded - "other types of transfer, such as air-to-air, are not currently in the scope of this document". The document also states it "does not require use of any specific network or transport protocols, as those are dependent upon the data link used", though conditional requirements apply "when specific other protocols are used" - the UDP framing rule below is one of those.

The requirements

Three requirements sit on top of the base CFDP protocol. Where a file transfer system also implements STANAG 4586/AEP-84 (Standard Interfaces of Unmanned Aircraft (UA) Control System (UCS) for NATO UA Interoperability), it reuses that ID: "they shall use their STANAG 4586/AEP-84 ID as their CFDP Entity ID". Every Protocol Data Unit carries its own check: "file transfer systems shall include a Cyclic Redundancy Check (CRC) in each PDU in accordance with Section 4.1.1 of the CFDP Standard". Over a UDP network, framing is fixed: "the sending system shall transmit one PDU per UDP packet".

Choosing a transfer mode

CFDP offers two modes the document calls classes, and roughly half of AEDP-4858 is worked examples for choosing between them. Class 1 is one-way - "no packets are sent from the receiver of the file to the sender of the file" - and suits a receiver that must "maintain radio silence" rather than reveal its position, typically over multicast so "the receiver address does not have to be known in advance." Class 2 is two-way: "these transfers allow the receiver to notify the sender of missed packets so the sender can re-send the missed packets," generally faster because the sender is not sending redundant data on the chance a packet is lost. AEDP-4858 works through four mission pictures - a single two-way ground station, a single silent receive-only station, a mixed pair, and multiple receiving stations - and treats the choice of class as a mission-by-mission engineering decision, not a fixed default.

How it is checked

AEDP-4858 names no inspection, audit or certification mechanism. It states the protocol and framing requirements a file transfer system must meet and says nothing about how, or by whom, compliance with them is checked - no accredited certification body, no government surveillance role, no notified body and no self-declaration process appears anywhere in the document.

Standards it references

• STANAG 4586Background
• AEP-84Background