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EDI communication protocols: which one suits your partner?

The common EDI communication protocols are AS2, OFTP2, SFTP, HTTPS interfaces (APIs), email and, in some industries, X.400 over a VAN. You rarely choose on your own: usually the customer or supplier specifies the transmission method in its EDI implementation guide. This page shows how the methods differ and what you need to watch out for during setup.

Last updated 18 October 2026 · fokus it solutions, Jens Musleh

Format and transmission method are two questions

An EDI connection has two levels that often get mixed up:

  • The format determines how the content is structured: EDIFACT, VDA, XML or CSV. More on this under EDIFACT explained.
  • The transmission method determines how the file gets from one computer to the other: AS2, OFTP2, SFTP and so on.

The levels are independent. An EDIFACT invoice can travel via AS2, OFTP2 or SFTP. A VDA delivery schedule often arrives via OFTP2, although technically it could come another way. So if your customer requires “EDI”, you need both answers: which format and which method.

EDI transmission methods at a glance

AS2

AS2 sends files over HTTP directly to the partner, signed, encrypted and with an acknowledgement of receipt, the MDN. It is based on RFC 4130. AS2 is not tied to any industry. Details: AS2 explained.

OFTP2

OFTP2 is the automotive industry's protocol, maintained by Odette and described in RFC 5024. It runs over its own TCP connection (port 6619 with TLS), uses certificates and acknowledges every file with an EERP. Details: OFTP2 explained.

SFTP

SFTP transfers files over an SSH connection (Secure Shell, RFC 4251; default port 22). Usually one side provides a directory, and the other places files there or collects them. The connection is encrypted, but there is no acknowledgement at file level. You only find out whether a file was processed through a response message or an agreement, such as “the file is deleted after collection”.

HTTPS interface (API)

An API connection means that the partner provides a web address to which your system sends data or from which it retrieves data, usually as JSON or XML. The connection is encrypted with TLS (RFC 8446), and authentication uses keys or tokens. Every API is structured differently, so each one needs its own connection.

Email

Email is the simplest method: the EDI file is attached to an email. RFC 1767 describes how EDI data is packaged in MIME emails; AS1 (RFC 3335) added signatures and acknowledgements. In practice, a plain email is neither signed nor acknowledged. It is still used for small volumes or as a temporary solution.

X.400 and VAN

With X.400, the ITU-T describes a series of standards for message handling systems; it lists versions from 1988 onwards, and the 1999 version is the one in force. A VAN (value-added network) is a service provider's network with mailboxes through which partners exchange data without connecting directly. X.400 can still be found in retail: German clearing centres such as cctop and EDI Fuchs include it in their price lists, EDI Fuchs for example as a surcharge from €10 per month per message type and partner.

Comparison table

Method Where it is common Security Acknowledgement of receipt Effort for you
AS2 across industries signature and encryption per file, optional TLS yes, MDN (can be signed) medium: software, certificate, reachable address
OFTP2 automotive industry TLS, certificates, file signing and encryption possible yes, EERP (can be signed) medium to high: software, Odette ID, certificate, port 6619
SFTP across industries SSH-encrypted connection no, only by agreement or response message low: access and key
HTTPS/API wherever the partner offers an API TLS, authentication by token or key depends on the API (response code, status) a separate connection for each API
Email small volumes, temporary solutions plain email unprotected, encryption only with add-ons no (yes with AS1) low, but error-prone
X.400/VAN parts of retail within the provider's network depends on the network contract with a VAN provider, ongoing fees

The “Where it is common” column is a rough guide. What counts is what your partner requires in its implementation guide.

What to consider when choosing

If you do have a choice, three questions help:

  1. Do you need proof that the file has arrived? For despatch advices and invoices, you usually do. Then AS2 and OFTP2 have the advantage, because the acknowledgement is part of the protocol.
  2. Who opens the connection? With AS2 and OFTP2, the partner often sends to you actively. For that, your server needs a fixed address and an open inbound port. With SFTP or an API, you can also collect the data yourself, without opening a port in your firewall.
  3. How many partners use the same method? Every additional transmission method is another component that has to be run, monitored and supplied with certificates.

As for security: a method with an encrypted connection is sufficient for a lot of data. Signed files and acknowledgements are worthwhile if there could later be a dispute about receipt or content.

Transmission costs

The specifications of AS2, OFTP2, SFTP and HTTPS are freely available as RFCs. Costs arise for software, certificates, for OFTP2 the Odette ID, and operation. With X.400 and VANs, the network operator's ongoing fees come on top. How it all adds up is shown in What does an EDI connection cost?.

Transmission methods with edi-service.eu

edi-service.eu supports OFTP2, AS2, SFTP, HTTPS and email, inbound and outbound. X.400 and VAN mailboxes are not included. If a partner can only be reached that way, you need an additional route, such as a clearing centre for that partner alone, or the partner switches to AS2 or OFTP2. Our OFTP2 component is not Odette-tested; we clarify this in advance if your customer requires tested software. What the price covers is set out under Price.

Frequently asked questions

Which EDI communication protocol is best?

There is no single best method; usually your partner decides. OFTP2 is widespread in the automotive industry, while other industries use AS2, SFTP or an API depending on the partner. SFTP is easy to set up but does not provide an acknowledgement of receipt.

Is email good enough for EDI?

For small volumes and as a temporary solution, it can be, if your partner accepts it. But a plain email is neither signed nor acknowledged, and mailboxes sometimes filter out attachments. For despatch advices and invoices, a method with an acknowledgement is the safer choice.

What is a VAN, and do I need one?

A VAN is a service provider's network in which every participant has a mailbox. You only need one if a partner can only be reached that way, for example via X.400. Direct connections via AS2, OFTP2 or SFTP do not need a VAN.

Does my server have to be reachable from the internet?

With AS2 and OFTP2, usually yes, namely when the partner sends to you actively. You then need a fixed address and an open port. With SFTP or an API where you collect the data yourself, an outbound connection is enough.

Would you like us to check whether your partners' transmission methods are a good fit for edi-service.eu? Send an enquiry

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