Applicability Standard 3 (AS3) is a message-based protocol developed for transmitting electronic data interchange (EDI) securely using FTP or FTPS. It is part of the Applicability Statement (AS) series maintained by the Internet Engineering Task Force (IETF) and uses digital signatures and encryption to ensure message integrity, non-repudiation and confidentiality. Unlike AS2, which supports real-time HTTP-based delivery, AS3 allows for asynchronous communication, which makes it ideal for systems where direct, always-on connections are impractical. Messages are structured as MIME attachments and stored on FTP servers, where recipients retrieve them on their schedule. This architecture supports pull-based workflows that fit organizations with intermittent connectivity or strict inbound firewall rules. AS3 is commonly used in supply chain environments that require standards-based EDI exchanges without continuous connectivity.
Core AS3 features
AS3 offers several features that make it suitable for secure, flexible B2B file exchange, especially when compared to real-time EDI protocols. Some of these features include that AS3:
- Enables asynchronous file retrieval and is deal for environments without persistent internet access
- Leverages MIME formatting for message structure to allow interoperability with other AS protocols
- Provides message disposition notifications (MDNs) for delivery confirmation
- Supports digital signatures and encryption for secure, authenticated transfers
- Uses FTP or FTPS for transport to support both encrypted and non-encrypted environments
These features allow organizations to maintain secure EDI workflows while accommodating varied technical and security requirements.
How AS3 works
AS3 transmits messages as MIME-formatted files over FTP or FTPS. The sender digitally signs and optionally encrypts the message before uploading it to an FTP server accessible by the recipient. The recipient then connects to the server, retrieves the message and sends an MDN back to the sender as acknowledgment. Unlike AS2, this process does not require a persistent HTTP connection, which is why AS3 is ideal for batch transfers or environments behind strict firewalls. Because FTP is inherently unidirectional, AS3 is well-suited for organizations that prefer or require pull-based workflows.
AS3 security and compliance
AS3 supports encryption and digital signatures for secure file transfers. These features help ensure message integrity, protect against tampering and enable non-repudiation. While FTP alone is not secure, AS3’s support for FTPS adds TLS-based encryption, which makes it suitable for regulated industries. Enterprises leveraging AS3 for EDI gain added assurance through MDNs that provide traceable confirmation when files are received and validated. When properly configured, AS3 meets compliance requirements for financial, healthcare and supply chain communications.
AS3 and MFT
AS3 integrates with MFT platforms to support EDI alongside other protocols like AS2, OFTP2 and SFTP. MFT platforms provide centralized control, automation, logging and encryption, which are key features that enhance AS3’s flexibility. Enterprise organizations benefit from the ability to manage AS3 within broader automation workflows, monitor transfer activity and enforce access controls. As part of a comprehensive MFT solution, AS3 helps standardize secure partner communication across disparate systems and processes.
AS3 FAQs
What is AS3 in EDI?
AS3 is a protocol that sends EDI messages over FTP or FTPS. It uses digital signatures and encryption to keep data safe. It does not need both the sender and receiver online at the same time. This works well when partners are in different time zones or have strict network rules.
AS3 is not real-time like AS2. It lets the sender upload a message to a secure server. The recipient can download it later. This pull method gives more control. It helps businesses lower system demands. It also supports setups that are more spread out or loosely connected.
What is the difference between AS2 and AS3?
AS2 is a real-time protocol that sends messages using HTTP or HTTPS. AS3 works in a delayed way and uses FTP or FTPS. AS2 needs both the sender and receiver to be online during the transfer. AS3 lets one user upload and the other download at different times.
This setup affects when each is used. AS2 fits tasks that need fast replies and quick handling. AS3 works well for batch jobs or when connections are not steady. Both protect data with encryption. They also check message integrity. Their main difference is in how they move data and connect systems.
When should you use AS3?
AS3 is ideal when trading partners do not have persistent connectivity or when firewalls limit inbound HTTP traffic. It is also a strong fit for organizations that prefer asynchronous, batch-based workflows and already maintain secure FTP infrastructure.
Use cases include supply chain communications, scheduled financial data transfers and situations where trading partners cannot or will not implement AS2. AS3 enables EDI compliance without the need for always-on systems, which makes it a flexible choice for global B2B file exchanges.
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