Kind of AS2 Failures in EDI and How to Fix

 

✅ MDN Errors in AS2 – Overview and Resolution

In AS2 (Applicability Statement 2), an MDN (Message Disposition Notification) is an electronic receipt that acknowledges the successful or failed delivery of a message. When issues occur during AS2 communication, MDN errors are generated, indicating problems with message transmission, validation, or decryption.

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🔥 1. What is an MDN in AS2?

• An MDN is a receipt confirmation sent by the receiver to the sender, verifying whether the message was:
  • Received successfully
  • Decrypted correctly
  • Validated without issues
• The MDN contains:
  • Disposition: The final status (e.g., processed, failed, or rejected).
  • MIC (Message Integrity Check): A hash value used to verify message integrity.
  • Digital signature: To ensure authenticity.
• MDN types:
  • Synchronous MDN: Sent immediately after receiving the message.
  • Asynchronous MDN: Sent later (within a specific time window).

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🔥 2. Common MDN Error Types and Resolution

Below are the most common MDN errors encountered in AS2 communication, along with their causes and resolutions:

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🛑 ❗ 1. MIC Mismatch Error

Error:

MIC mismatch: Received MIC does not match the expected MIC

Cause:

• The Message Integrity Check (MIC) received in the MDN does not match the MIC calculated by the sender.
• This occurs due to:
  • Data corruption during transmission.
  • Incorrect hashing algorithm (e.g., SHA-1 vs. SHA-256 mismatch).
  • Data compression or encoding issues.

Resolution: ✅ Check hashing algorithm consistency:

• Ensure both sender and receiver use the same MIC hashing algorithm (SHA-1, SHA-256, or MD5).
• Go to Trading Partner → AS2 configuration → MIC Algorithm → Verify that both ends use the same hash algorithm.

✅ Check data integrity:

• Verify that the payload data and signature are not modified or corrupted.
• Re-transmit the AS2 message.

✅ Enable content transfer encoding:

• Ensure consistent encoding (e.g., Base64) to prevent corruption.
• In IBM Sterling B2B Integrator, enable Base64 encoding under AS2 settings:
  • Enable Content-Transfer-Encoding: Base64.

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🛑 ❗ 2. Signature Verification Failed

Error:

Signature verification failed. Invalid signature in the MDN.

Cause:

• The MDN signature does not match the sender’s signature.
• This occurs due to:
  • Expired or invalid certificate.
  • Incorrect partner certificate mapping.
  • Signature algorithm mismatch.

Resolution:
✅ Verify certificates:

• Go to Trading Partner → Certificate Management.
• Verify that the partner’s certificate is valid and not expired.
• Ensure the correct certificate is used for signing and verification.

✅ Certificate mapping consistency:

• Ensure the correct public certificate of the partner is configured in AS2 settings.
• Re-import the valid certificate if necessary.

✅ Update signature algorithms:

• Ensure both sender and receiver use compatible signature algorithms (SHA-1, SHA-256, or SHA-512).
• In Sterling B2B, go to:
  • Trading Partner → AS2 Configuration → Signature Algorithm
  • Verify the same algorithm is used by both sides.

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🛑 ❗ 3. Invalid MDN Format

Error:

Invalid MDN format: Missing fields or malformed MDN response.

Cause:

• The MDN received is incomplete or corrupted.
• Common causes:
  • Incorrect MIME formatting.
  • Empty MDN or missing content.
  • Incorrect AS2 header settings.

Resolution:
✅ Check MDN structure:

• Go to Operations → System Logs → AS2 logs.
• Inspect the MDN headers and body.
• Verify if the MDN contains:
  • Disposition: status
  • Content-Type: header
  • MIC: value

✅ Fix MIME formatting issues:

• Ensure that the partner uses standard MIME formatting.
• Add proper Content-Disposition and Content-Transfer-Encoding headers in the AS2 settings.

✅ Enable proper AS2 headers:

• Verify that the MDN includes:
  • Content-Type: multipart/signed
  • Content-Transfer-Encoding: base64

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🛑 ❗ 4. MDN Not Received / Timeout

Error:

MDN not received: Timeout error

Cause:

• The MDN was not received within the expected timeframe.
• This happens due to:
  • Asynchronous MDN delays.
  • Network issues.
  • Partner system issues.
  • Incorrect AS2 URL or port.

Resolution:
✅ Verify AS2 URL and port:

• Go to Trading Partner → AS2 Configuration → AS2 URL.
• Confirm that the URL and port are correct.
• Ensure that the AS2 URL is reachable:

telnet <partner_URL> <port>

✅ Check firewall settings:

• Ensure firewall rules allow AS2 communication on the required port (typically 8080 or 8443).

✅ Extend MDN timeout:

• In IBM Sterling, increase the MDN timeout to allow sufficient time for asynchronous MDNs:
  • Trading Partner → AS2 Settings → MDN timeout → 5-10 minutes

✅ Resend the message:

• If the MDN is not received, resend the AS2 message.

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🛑 ❗ 5. AS2 Decryption Failure

Error:

Decryption failed: Invalid private key or decryption error

Cause:

• AS2 message decryption failed due to:
  • Incorrect private key used for decryption.
  • Mismatched encryption algorithm.
  • Corrupted or invalid payload.

Resolution:
✅ Verify encryption certificate:

• Go to Trading Partner → AS2 Configuration → Certificate Management.
• Ensure the correct private key is configured for decryption.
• If the decryption key is incorrect, re-import the correct key.

✅ Ensure algorithm compatibility:

• Confirm that both sender and receiver use the same encryption algorithm (AES-256, AES-128, or Triple DES).

✅ Validate encryption settings:

• Check encryption preferences in Sterling:
  • AS2 Settings → Encryption Algorithm → AES-256

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🛑 ❗ 6. AS2 Compression Error

Error:

Invalid compressed data format

Cause:

• The message was compressed incorrectly or the receiver could not decompress it.
• This happens due to:
  • Unsupported compression algorithm.
  • Corrupted compressed data.

Resolution:
✅ Disable or update compression:

• If compression causes issues, disable compression temporarily.
• In IBM Sterling, go to:
  • Trading Partner → AS2 Configuration → Compression → Disable
• If compression is required:
  • Ensure both sender and receiver use compatible compression algorithms (ZLIB, GZIP).

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🎯 ✅ Key Takeaway: Resolving MDN Errors in AS2

To resolve MDN errors in IBM Sterling B2B Integrator:

1. Check MIC and Signature: Ensure MIC algorithms and certificates match.
2. Review AS2 configuration: Verify URL, port, and partner settings.
3. Increase MDN timeout: Allow more time for asynchronous MDNs.
4. Enable consistent encryption: Use matching algorithms on both ends.
5. Check logs and re-transmit: Inspect AS2 logs, identify issues, and resend the message.
6. Verify compression settings: Ensure compression compatibility.

✅ By systematically troubleshooting these MDN errors, you can effectively resolve AS2 communication issues.