What is the difference between AS2-Version: 1.1, and AS2-Version: 1.2.?

AS2 (Applicability Statement 2) is the open specification standard by which vendor applications communicate EDI (Edifact or X12), XML, and binary data securely via the Internet.

The definition for AS2-Version 1.1 can be found at:

http://www.ietf.org/rfc/rfc4130.txt

The definition for AS2-Version: 1.2 can be found at:

http://www.ietf.org/internet-drafts/draft-meadors-ediint-features-header-03.txt

in short, AS2-Version: 1.2 adds the new optional features described below. A message packaged by AS2-Version: 1.1 can be fully understood by AS2-Version: 1.2 applications. But an AS2-Version: 1.1 application cannot understand the new features of AS2-Version: 1.2.

Certificate exchange messaging (CEM) is a standard for EDIINT trading partners to exchange public-key certificates, replacing certificates that have expired, been compromised or need replacing for some other reason.

Multiple Attachments. AS2 transmissions generally contain only a single EDI or XML payload document. The multiple attachments feature allows for two or more documents to be sent in a single AS2 transmission.

Filename Preservation is a method for preserving the filename associated with a payload as provided in the Content-Disposition MIME header [RFC 2183].