A multi-source agreement, commonly known as a MSA, is an agreement between manufacturers to make products that have the same basic functionality and operability across different vendors. MSAs act as de facto standards, establishing and promoting a competitive market for interoperable products instead of a monopolistic structure. It means that all suppliers (including suppliers of third party compatible modules) can compete on equal terms to gain their share of the market. This helps drive down costs for the end user and gives more freedom for customers to choose the suppliers they want to buy from. Put simply, you can purchase optical transceivers from any vendor you want, so long as they meet the standards set out within the relevant MSA.