From SFP and QSFP to today's QSFP-DD and OSFP form factors, MSA specifications define how optical modules are mechanically, electrically, and logically designed—ensuring that products from different vendors can work together reliably. Understanding MSA is critical for compatibility validation, cost. The MSA stands for Multi-Source Agreement and is an agreement between multiple manufacturers to implement standards for optical modules. They are designed to provide the same basic functionality and operability across different suppliers and companies.