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What's the Difference AS3 vs. AS4

AS3 vs. AS4: What is the Distinction?

If you have ever delved into the Applicability Statement family tree, you may know that AS3 and AS4 don’t have much in common. But what makes these two ostensibly sequential protocols similar, and what sets them apart? And why aren’t they sequential, anyway? Read on to discover the key details that differentiate AS3 and AS4, and what makes them stand out among file transfer protocols.

How the Applicability Statements Got Started

Way back in the day, HTTP and AS2 were both great ways to send data from point A to point B, but neither were ideal for large file transfers. So AS3 was released to handle those large file transfers – but AS2 was quickly fixed to do the same. And, because it was already more widely used than AS3, organizations stuck with AS2 for their file transfers, a secure way to move large files between two points.

Then, instead of becoming the answer to large file transfer issues, AS3 pivoted and expanded the Applicability Statement realm in a new direction.

Finally, a worthy successor to AS2 was born: Applicability Statement 4 (AS4). AS4 technically supersedes AS2 – it includes new technologies, improved features, and more – but AS2 is still widely used.

What is AS3?

AS3 is a message standard used to transfer messages between trading partners in their preferred format. Rather than being the next version of AS2, AS3 can be considered a “point 5” step up – or a step in a new direction entirely. AS3 is not wholly considered a “protocol.” Instead, AS3 helps to abstract the transfer mechanism from the message being sent.

Here’s how it works: once an AS3 message is composed, it can be conveyed via any other protocol – FTP, SFTP, HTTPS, and others – as long as both the sender and recipient can access the message’s location.

AS3 Features

  • MDN receipts are always delivered asynchronously
  • AS3 abstracts the protocol from the message being sent, making it very versatile for transferring files securely
  • Push/pull protocol

What is AS4?

AS4, the spiritual successor to AS2, is a B2B file transfer protocol that offers new benefits to users over AS2. AS4 incorporates components from other successful file transfer protocols to improve security, reliability, and flexibility, and is among the most complex and most customizable file transfer protocols.

AS4 Features

  • Push/pull protocol
  • Offers secure B2B exchange
  • As it’s EDI-friendly, AS4 can help to simplify EDI integration
  • Tamper-proof: AS4 messages can’t be modified in transit without the changes being detected, and receipts are delivered as SOAP
  • Payload agnostic, supporting a multitude of document formats including EDI X12, EDIFACT, HL7, XML, JSON, binary, and ASCII

When to Use AS3 and When to Use AS4

Both AS3 and AS4 give users ways to securely get their messages to recipients and track message reception and non-repudiation.

  • Request a receipt: AS3 provides receipts to confirm messages were received, and AS4 provides MDNs (Message Disposition Notifications) to simplify file transfer tracking. Plus, non-repudiation helps to legally prove unadulterated transactions for both AS3 and AS4.
  • Secure your file transfers: AS3 can use secure file transfer protocols to ensure end-to-end encryption, whereas in AS4, document security is achieved with aspects of WS-Security, XML Encryption, and XML Digital Signatures.
  • Fulfill specific requirements: While AS3 can transfer nearly all protocol types, it’s an especially helpful upgrade for organizations using FTP for scripts, apps, or security. AS4 is useful with EDI requirements and the secure exchange of B2B messages with trading partners.
  • Push and pull your messages: Both AS3 and AS4 are push/pull protocols, so do not require ongoing connections to ensure data is sent and received.
  • Send anything: Both AS3 and AS4 are well-equipped to send large files. AS3 allows users to send any data type, and AS4 is payload agnostic, and can also send multiple payloads in one AS4 message.
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