Which solution will meet these requirements?

Explanations:

AWS DataSync is primarily used for transferring files between on-premises storage and AWS, or between AWS storage services. It does not support the AS2 protocol natively, nor does it offer integrated user authentication through an IdP. While a Lambda function could handle authentication, this approach does not align with AS2 requirements.

Amazon AppFlow is designed for integrating and transferring data between AWS services and SaaS applications, but it does not natively support the AS2 protocol. An Amazon ECS task could handle IdP authentication, but again, this solution does not meet the requirement for AS2 data transfer.

AWS Transfer Family supports various protocols for transferring files, including AS2. It can directly integrate with AWS services while allowing for user authentication through AWS Lambda, which can interact with the company’s IdP to authenticate users during data transfer operations. This solution meets all the stated requirements.

AWS Storage Gateway is used for connecting on-premises environments with AWS cloud storage but does not natively support the AS2 protocol for data transfers. Additionally, Amazon Cognito is typically used for user authentication in web and mobile applications, but it may not effectively serve the specific IdP requirements for the AS2 protocol in this context.