Mastering Your EDI AS2 Connection: Setup Tips and Common Pitfalls

August 15, 2014

Topics: AS2, Cloud-based EDI, Data Security, EDI testing, EDI VAN, Managed Services

Mastering Your EDI AS2 Connection Having been deemed the “AS2 Queen” in certain EDI circles, I thought it would be helpful to share all that I have learned about AS2 communication in the 20 years I have been implementing it. Let’s start by explaining exactly what AS2 is and why it’s important. First of all, AS2 stands for Applicability Statement 2 and is a secure, encrypted point-to-point connection between two organizations. The use of encryption and digital certificates ensures that the data is sent securely. You’ll find that some of your customers or suppliers require AS2, with Walmart being the most notorious, while others require VAN (value-added-network) only. The good news is that today, most VAN platforms have options for AS2 so you no longer have to buy special software to accomplish EDI AS2 connections.

What’s more is that many fully managed cloud EDI platforms offer AS2 as a standard component. The biggest reason AS2 has grown in popularity is that it’s typically more cost effective since you’re not paying by the kilo character (KC) like with most VANs. All that said, AS2 can be thorny though to set up, especially when it is your first time doing so. Once the setup has been completed and your firewall tuned to support it, it does get a bit easier each time you set up a new AS2 connection. As they say, practice makes perfect.

Table of Contents

How an EDI AS2 Connection Works
Five Common Pitfalls in EDI AS2 Communication
Troubleshooting AS2 Issues Quickly
Checklist for Smooth AS2 Connection Setup
Optimizing AS2 Connection Setups for Long Term Success

How an EDI AS2 Connection Works

Overview of Inbound vs. Outbound Communications

In the context of AS2 , communication can be classified into two primary types: inbound and outbound. Both types refer to the direction in which data is transmitted between trading partners but differ in terms of the sender and receiver roles.

Inbound Communication refers to the reception of data from a trading partner. In this scenario, the recipient of the message initiates the process of accepting the data by validating the message’s authenticity and integrity. The inbound process begins once the sending partner transmits the data, using the AS2 protocol over the internet.
Outbound Communication involves the sending of data to a trading partner. The initiating party in an outbound transaction prepares the message, digitally signs it, and sends it over the secure AS2 connection to the recipient. The recipient then processes the data upon receipt and sends an acknowledgment message (MDN, or Message Disposition Notification) confirming the transaction’s successful delivery or processing.

Both inbound and outbound communications leverage secure protocols to ensure that data is transmitted in a compliant, efficient, and non-repudiable manner, with built-in mechanisms for encryption and validation.

Role of AS2 URLs, Ports, and Digital Certificates

AS2 communication relies on specific technical components to ensure secure and efficient transmission of data. These components include AS2 URLs, ports, and digital certificates, each playing a crucial role in the setup and operation of the AS2 connection.

AS2 URLs: The AS2 URL is a unique identifier that points to the endpoint of a trading partner’s AS2 server. It typically includes the server’s domain name or IP address, along with a path indicating the AS2-specific directory where messages are handled. For example, an AS2 URL might look like https://as2.partner.com:5000/receiver. This URL directs the sending party to the correct destination for transmitting or receiving AS2 messages.
Ports: AS2 messages are typically transmitted over port 80 (HTTP) or port 443 (HTTPS) to ensure the use of secure, encrypted communications. Port 443 is preferred as it ensures that all data is transmitted utilizing SSL/TLS encryption, providing confidentiality and integrity of the exchanged information. Configuring the correct ports is essential to the reliable functioning of the AS2 EDI connection.
Digital Certificates: Digital certificates play a central role in authenticating the identities of the communicating parties and securing the data. They are used for both signing the messages (ensuring their integrity and authenticity) and encryption (securing the data during transmission). These certificates are issued by trusted Certificate Authorities (CAs) and are crucial in preventing unauthorized parties from intercepting or altering the messages. Digital certificates ensure non-repudiation, meaning that once a message is sent and signed, neither the sender nor the recipient can deny the transaction.

Together, these elements form the technical foundation for secure, reliable AS2 communication, where each component must be properly configured to prevent potential vulnerabilities or miscommunications.

Differences Between AS2 and Other EDI Transmission Methods

AS2 stands out from other EDI (Electronic Data Interchange) transmission protocols due to its reliance on internet-based communication, enhanced security features, and real-time capabilities. Several key differences between AS2 and other traditional EDI transmission methods are worth noting:

Security

AS2 uses HTTPS (SSL/TLS encryption) for secure data transmission, ensuring confidentiality and integrity during the entire communication process. This contrasts with older protocols like FTP or FTPS, which although are still applicable and valid, may not inherently offer the same level of robust encryption, unless explicitly configured to do so. While traditional VANs can provide secure transmission, AS2 offers the advantage of end-to-end encryption directly over the public internet, reducing reliance on third-party intermediaries.
Real-Time Capabilities

AS2 supports real-time or near-real-time communication, meaning that messages can be sent and received immediately as needed. Other protocols like FTP, SFTP, or even AS1 (a predecessor to AS2) may have inherent delays in their message handling or require batch processing, which is less efficient in time-sensitive business environments. AS2 enables instantaneous communication, which is particularly useful for industries with fast-paced transactional needs, such as retail or manufacturing.
Message Acknowledgment

One of the defining features of AS2 is the MDN, an automatic acknowledgment sent by the recipient to confirm that the message has been successfully received and processed. This offers a higher level of assurance compared to other methods, such as FTP or SFTP, where manual acknowledgments or additional tracking mechanisms might be necessary. The MDN serves as a proof of receipt, adding a layer of accountability and transparency in transactions.
Cost and Complexity

Compared to other protocols such as EDI over VAN or AS1, AS2 is often considered more cost-effective, as it eliminates the need for third-party network services. VANs typically require subscription fees and additional infrastructure, whereas AS2 operates directly over the internet, with costs related primarily to software and certification fees. However, AS2 implementations can be technically complex, requiring careful configuration of certificates, endpoints, and ports, which may pose challenges for smaller organizations or those lacking internal technical expertise.

Five Common Pitfalls in EDI AS2 Communication

While AS2 offers a secure and efficient method for exchanging electronic data, there are several common pitfalls that organizations must navigate to ensure smooth communication. Even minor configuration mistakes can lead to delays, failed transmissions, or security vulnerabilities. Below are some key challenges businesses face when implementing AS2 communication:

1. Incorrect Port Configuration

Inbound

For AS2 inbound communications, make sure your AS2 trading partner is using the correct port that you are expecting them to communicate to you with. This port should have been configured to listen for AS2 traffic from within your AS2 application. The port is referenced in your AS2 URL that you have provided to them.

Outbound

For AS2 outbound communications, ensure your AS2 application server can communicate using your AS2 trading partner’s designated AS2 port when sending data to your trading partner. Your AS2 trading partner will provide you with the correct port to use when communicating with them as part of their AS2 URL.

2. Firewall Configuration Issues

Inbound

For AS2 Inbound communications to be successful, your firewall must allow for AS2 communications via an AS2 specified port. This port must be open on your firewall. This can be done many ways. Your firewall may be locked down and only allow certain IP addresses to communicate through the AS2 designated port. It is important to obtain a list of sending IP addresses from your AS2 trading partners and limit permissions on your AS2 port to only those sending IP addresses that you authorize to lower your vulnerability. This is the preferred method. However, I have also seen firewalls that have been configured to allow for all traffic to come through on an AS2 designated port although I do not recommend this.

Outbound

For AS2 Outbound communications to be successful, ensure your firewall allows for your AS2 application to send out via your trading partner’s AS2 port. This will be the port they expect you to be sending data to them on. In most companies, all outgoing internet traffic is allowed when it is initiated from within their own firewall. Some companies will go so far as to lock down their firewall to only allow their AS2 applications to send using the specific ports that were requested by their AS2 Trading Partners.

Keep in mind that your trading partner’s firewall may also have to be considered for both AS2 inbound and AS2 outbound communications. They may have to open your AS2 designated port to be able to communicate to you for AS2 inbound communications to work. Also, they may have their AS2 designated port restricted to only allow certain EDI trading partner sending IP addresses as well. They may need to add your sending IP addresses to their firewall. Make sure you ask the question up front to find out if they need your sending IP addresses for their firewall updates.

You also may find that you may have additional firewall rules that change the IP address going out so you must obtain the correct sending IP addresses from your network administrator. Many times there are internal NAT translations and port forwarding rules that take place that we are not aware of as they happen behind the scenes.

3. AS2 URL and Protocol Errors

Inbound

For AS2 Inbound, make sure that you have provided the correct AS2 URL to your AS2 trading partners. It may be in the format of the following: http://edi.abccompany.com:7070/abccompanyas2id where edi.abccompany.com may be your DNS name that resolves back to an external IP address that is rerouted to your AS2 application, port 7070 is your AS2 designated port, and abcompanyAS2ID or your trading partner’s AS2ID may be the virtual folder for them to communicate data to.

Outbound

For AS2 Outbound, make sure you are using the correct AS2 URL to send out. Your AS2 trading partner will provide this to you.

For https vs. http, there may be additional configuration requirements as well within your AS2 application and on your AS2 trading partner’s configuration as well.

4. AS2 ID Mismatches

It’s important to ensure that you are utilizing the correct AS2 sender ID and receiver ID for each AS2 connection. The AS2 IDs are case sensitive and both parties’ AS2 IDs must exactly match for the connection to take place.

5. Digital Certificate Challenges

You must reference the correct certificates for signing and encrypting when setting up your AS2 Inbound and Outbound configurations. If any of the certificate serial numbers are not the same on both sides, the connection will be refused.

Troubleshooting AS2 Issues Quickly

When using AS2 for EDI (Electronic Data Interchange), it’s important to be prepared for troubleshooting potential issues. AS2, by its nature, is a complex protocol with several points of failure that can interrupt smooth communication. Understanding common error messages and knowing how to address them can significantly reduce downtime and keep your EDI processes running efficiently.

Common Error Messages and How to Address Them

AS2 communication relies on various configurations for success, and issues typically arise from misconfigurations or network problems. Some of the most common error messages and troubleshooting strategies include:

“Connection Timeout”
- Cause: This error usually occurs when the client cannot establish a connection to the AS2 server within the expected time frame. It could be a network issue or a firewall configuration blocking the connection.
- Solution: Verify that the correct ports (typically 443 for HTTPS) are open and not blocked by firewalls. Check the AS2 URL for typos or errors. Additionally, ensure that the network infrastructure is not restricting outbound or inbound connections.
“MDN Not Received”
- Cause: A Message Disposition Notification (MDN) is sent by the receiver to confirm the message was successfully processed. If the MDN isn’t received, it indicates a delivery or processing failure.
- Solution: Check if the recipient’s server is configured to send MDNs. Ensure both parties are using the same AS2 ID and that the communication path is correct. Also, check for any firewall settings that may block MDN responses.
“Invalid Digital Certificate”
- Cause: This error occurs when there is an issue with the digital certificate being used for encryption or signature verification, such as an expired or mismatched certificate.
- Solution: Verify the digital certificates used by both parties. Ensure that the certificate is not expired and that the public/private keys match. You must also check that the certificate is properly installed in the AS2 configuration. Regularly updating and renewing certificates is a best practice.
“AS2 ID Mismatch”
- Cause: AS2 IDs are unique identifiers for each trading partner. If the AS2 ID specified in the communication doesn’t match the one expected by the recipient, the message will fail.
- Solution: Confirm that the AS2 ID provided to the trading partner is correct. Both parties should exchange and verify the exact IDs before initiating any communication to avoid mismatch issues.
“Message Integrity Check Failed”
- Cause: This indicates that the integrity of the message was compromised, possibly due to tampering during transmission or an error in the digital signature.
- Solution: Verify the digital signature and hash algorithms used in the communication. Ensure that both parties are using compatible cryptographic methods. Re-send the message after correcting any discrepancies.

Practical Examples from Real-World Experiences

In practice, AS2 issues can stem from simple oversights or more complex network configurations. For example, one retailer experienced repeated “Connection Timeout” errors when attempting to send purchase orders to a supplier. After troubleshooting, it was discovered that the supplier’s firewall was blocking port 443, which was required for secure HTTPS communication. Once the firewall rule was adjusted to allow inbound connections on port 443, communication was successfully restored.

Another common issue arose when a manufacturer’s certificate expired. This caused the “Invalid Digital Certificate” error during every attempt to establish an AS2 connection with its partners. Upon verifying the certificate and updating it, the connection was re-established, and secure transmissions resumed.

Checklist for Smooth AS2 Connection Setup

Setting up an AS2 connection correctly from the beginning is crucial for long-term success. Here’s a step-by-step guide for a smooth AS2 setup:

Step-by-Step Guide for Initial Configuration

Exchange AS2 IDs: Before configuring, ensure that both parties agree on the AS2 IDs to use in the communication. This ensures proper identification of each party when sending and receiving messages.
Install Digital Certificates: Ensure that digital certificates (both public and private) are correctly generated and installed on both systems. These certificates will authenticate the sender and recipient and enable secure message encryption.
Configure AS2 URLs: Both parties should agree on the AS2 URL to which messages will be sent. This URL should point to a secure endpoint on the receiving system and be reachable through the internet or VPN.
Open Required Ports: Ensure that the necessary ports are open on both ends for secure communication. This is particularly important for port 443 for HTTPS communication. Double-check firewall settings to ensure that the ports are not being blocked.
Test the Connection: Once the configuration is complete, send a test between both systems to confirm the AS2 connection is functioning as expected. Look for successful transmission and those MDN responses.

Questions to Ask Trading Partners Upfront

When setting up an EDI AS2 connection with your trading partners, it’s critical to clarify several key points upfront to avoid configuration issues later on:

Firewall Rules: Are there any firewall rules that could block the AS2 connection? These could be restrictions on specific IP addresses or ports.
IP Addresses and Network Configurations: What are the IP addresses that need to be whitelisted for secure communication? We see this issue often. Are there any network configurations that could hinder the AS2 connection?
Protocols and Encryption: What version of AS2 will you be using? Are there specific encryption or hashing algorithms that need to be followed to ensure compatibility?

Optimizing AS2 Connections for Long-Term Success

Once your AS2 connection is up and running, it’s important to maintain and optimize it for long-term reliability and efficiency. Regular monitoring and auditing help identify potential issues before they disrupt your EDI processes.

Importance of Regular Audits and Monitoring

Performing periodic audits of your AS2 configurations and messages helps identify vulnerabilities and prevent breakdowns in communication. For example, monitoring for expired certificates, unauthorized IP access, or undelivered messages will address issues before they escalate. Auditing also ensures that your trading partners remain compliant with the agreed-upon protocols and security standards.

Tools to Automate AS2 Health Checks and Alert Systems

There are various tools available to help automate AS2 health checks, ensuring that your connections remain active and secure. These tools can check the status of digital certificates, verify that MDNs are being sent/received, and alert administrators of failures. Automated alerts notify users of any deviations from the normal functioning of the AS2 connection, allowing for quicker response times.

How AS2 Connections Fit Into a Broader EDI Strategy for Scalability

AS2 plays an important role in a modern, scalable EDI strategy. As organizations grow and expand their network of trading partners, the need for efficient, secure, and reliable communication increases. By implementing AS2, you create a foundation that can handle increased transaction volumes and accommodate new trading partners. AS2’s ability to operate over the internet, combined with its robust security and real-time capabilities, makes it an ideal choice for businesses looking to scale their EDI operations.

Achieving Seamless EDI AS2 Communication

Effective AS2 communication is essential for a smooth, secure, and scalable EDI strategy. By avoiding common pitfalls like incorrect port configurations, mismatched AS2 IDs, or expired certificates, you can ensure that your EDI processes run without interruptions. Regular audits, proactive troubleshooting, and the right tools for monitoring are all vital for maintaining long-term success.

As you can see, there is much to consider in setting up AS2 EDI connections with your trading partners. Between ports, firewall rules, URLs, AS2 IDs, and AS2 Digital certificates, it can take time diagnosing where the problem lies. It’s important to remember there can be issues on both sides of the communications. I hope this article helps you configure setup and diagnose issues, reducing time and effort for a successful AS2 connection.

Are you ready to set up or optimize your AS2 connection? Schedule a consultation with our team of EDI experts to ensure your communication systems are secure, efficient, and future-proof.