AS1, AS2, AS3 - The AS3 Protocol (Enterprise only)

The AS3 protocol is based on FTP. It is the latest ASx protocol developed and uses the same signing, encryption and MDN conventions used in the original AS1 protocol. After AS1, AS3 is probably the easiest ASx protocol to set up and work with (if firewall issues do not crop up), but AS3 still trails AS2 in terms of general acceptance.

How an AS3 File Transfer Works

Like any other ASx file transfer, AS3 file transfers typically require both sides of the exchange to trade SSL certificates and specific "trading partner" names before any transfers can take place. AS3 trading partner names can be any valid phrase.

1. You encrypt a data file with the public key on your partner's SSL certificate and sign it with the private key of your organization's SSL certificate as you bundle everything into an AS3 message. (Both the encryption and signing steps are optional, but should be used when possible.)
2. You send the AS3 message to an FTP server. This could be your FTP server, your partner's FTP server or a hosted FTP server somewhere else. (Credentials and cleartext message headers may be protected with SSL transport in this step.)
3. Your partner will retrieve your AS3 message off the same FTP server. (Credentials and cleartext message headers may be protected with SSL transport in this step.)
4. If the message is encrypted, your partner will decrypt it using the private key on his/her SSL certificate. If the message is signed, your partner will validate your signature using the public key on your SSL certificate. Your partner will also use the contents of the AS3 message to verify that the data file they now have is identical to the data file you sent them.
5. If you requested an MDN delivery receipt for your data file, your partner will calculate a cryptographic hash from the data file they received, sign the hash (and some other information) with the private key on their SSL certificate and create an MDN delivery receipt message. (The signing step is optional and controlled by the original message sender.)
6. Your partner will send his/her MDN delivery receipt message back to the same FTP server the original AS3 message traveled through, though perhaps in a different folder or bearing a different file name. (Credentials and the cleartext MDN delivery receipt message may be protected with SSL transport in this step.)
7. You will retrieve your partner's MDN delivery receipt message off the same FTP server. (Credentials and the cleartext MDN delivery receipt message may be protected with SSL transport in this step.)
8. You will inspect your partner's MDN delivery receipt message, making sure that you can verify his/her signature using the public key on your partner's SSL certificate and that the cryptographic hash calculated from your partner's copy of your data file matches the same hash calculation from your original data file.

Variations

FTP Server Location - The FTP server used in an AS3 transfer could be your FTP server, your partner's FTP server or a hosted FTP server somewhere else. If you have control over the FTP server, we recommend deploying/using a MOVEit DMZ FTP server.

MOVEit Implementation of AS3

MOVEit Central is the only MOVEit product required to send or receive files using AS1. In either case files and MDNs are sent through FTP servers, and we recommend deploying/using a MOVEit DMZ FTP server when possible.

...Using Your FTP Server

...Using Your Partner's FTP Server (Or a Hosted FTP Server)

See also:

• AS1, AS2 and AS3 - Hosts - AS3
• AS1, AS2 and AS3 - Tasks - AS3 - Source
• AS1, AS2 and AS3 - Tasks - AS3 - Destination

Advantages/Disadvantages of AS3 (Compared to AS1 and AS2)

AS3 was developed to add ASx file transfer capabilities to the well-established FTP/SSL ("FTPS") protocol. Also, using FTP as a transport rather than HTTP seemed to address the "no standard regarding username/password" limitation of AS2: most FTP servers already require username/password. The AS3 protocol is generally recognized by various industries as the "next" ASx protocol, but movement toward AS3 from established AS2 users has not been rapid.

Advantage: If you have an AS3 client and access to an FTP server, you can send and receive AS3 transmissions. You do not need to control or host the FTP server participating in an AS3 transmission, so AS3 ranks just behind AS1 in terms of easiest ASx protocols to install and configure as long as firewall issues are not much of a concern.

Disadvantage: AS3 has frequent firewall issues. AS3 is built on the FTP/SSL protocol, one of the most firewall-unfriendly protocols in use today. Some of the common issues involving FTP/SSL involve NAT translation, multiple data ports and improper translation of FTP commands by intervening firewalls. (Some people look for SSH and/or HTTP file transfer solutions specifically to avoid reoccurring FTP/SSL firewall issues; MOVEit products offer several tactical solutions for various FTP/SSL issues in terms of features and support.)

Disadvantage: No AS3 transmission mode is as fast as AS2 "synchronous MDN" transfers. This is likely the issue that keeps established many ASx players from moving from AS2 to AS3. When AS2 senders request on-the-fly "synchronous MDNs" for their small file transfers (such as part orders), AS2 is by far the fastest ASx protocol. The AS3 protocol does not support similar MDN-on-the-fly capabilities.

See also: Comparison of AS1, AS2 and AS3 on the "AS1, AS2 and AS3 - Overview" page.