AS2


AS2 is a specification about how to transport structured business-to-business data securely and reliably over the Internet. Security is achieved by using digital certificates and encryption.

Background

AS2 was created in 2002 by the IETF to replace AS1, which they created in the early 1990s.
The adoption of AS2 grew rapidly throughout the early 2000s because major players in the retail and fast-moving consumer goods industries championed AS2. Walmart was the first major retailer to require its suppliers to use the AS2 protocol instead of relying on dial-up modems for ordering goods. Amazon, Target, Lowe's, Bed, Bath & Beyond and thousands of others followed suit. Now, many other industries use the AS2 protocol, including healthcare, as AS2 meets legal HIPAA requirements.
In some cases, AS2 is seen as a way to bypass expensive value-added networks previously used for data interchange.

Technical overview

AS2 is specified in , and is based on HTTP and S/MIME. It was the second AS protocol developed and uses the same signing, encryption and MDN conventions used in the original AS1 protocol introduced in the late 1990s by IETF . In other words:
Like any other AS file transfer, AS2 file transfers typically require both sides of the exchange to trade X.509 certificates and specific "trading partner" names before any transfers can take place. AS2 trading partner names can usually be any valid phrase.

MDN Options

Unlike AS1 or AS3 file transfers, AS2 file transfers offer several "MDN return" options instead of the traditional options of "yes" or "no". Specifically, the choices are:

AS2 w/ "Sync" MDNs

Return Synchronous MDN via HTTP - This popular option allows AS2 MDNs to be returned to AS2 message sender clients over the same HTTP connection they used to send the original message. This "MDN while you wait" capability makes "AS2 Sync" transfers the fastest of any type of AS file transfer, but it also keeps this flavor of MDN requests from being used with large files.

AS2 w/ "ASync" MDNs

Return Asynchronous MDN via HTTP - This popular option allows AS2 MDNs to be returned to the AS2 message sender's server later over a different HTTP connection. This flavor of MDN request is usually used if large files are involved or if your trading partner's AS2 server has poor Internet service.

AS2 w/ "Email" MDNs

Return MDN via Email - This rarely used option allows AS2 MDNs to be returned to AS2 message senders via email rather than HTTP. Otherwise, it is similar to "AS2 Async ".

AS2 w/ No MDNs

Do not return MDN - This option works like it does in any other AS protocol: the receiver of an AS2 message with this option set simply does not try to return an MDN to the AS2 message sender.

Filename preservation

AS2 filename preservation feature will be used to communicate the filename to the trading partner. The banking industry relies on filenames being communicated between trading partners. AS2 vendors are currently certifying that implementation of filename communication conforms to the standard and is interoperable.
There are two profiles for filename preservation being optionally tested under AS2 testing:
For many businesses, the use of AS2 and electronic data interchange is not a choice so much as it is a requirement of doing business with a large customer or partner. That said, AS2 is a universal protocol that provides many benefits, from both business and technology vantage points.

Business case