What is the primary purpose of the Border Gateway Protocol (BGP)?

The primary purpose of the Border Gateway Protocol (BGP) is indeed to avoid routing loops between large networks. BGP is a standardized exterior gateway protocol that is used to exchange routing information between different autonomous systems on the internet. It helps in maintaining a stable and efficient routing table by determining the best paths for data to travel across interconnected networks.

BGP employs a path vector mechanism, which allows routers to keep track of the path taken by data packets. This prevents routing loops, which can occur when there are conflicting information or configurations in routing tables. By using attributes like AS path, next hop, and others, BGP ensures that data packets follow the most efficient and reliable paths across the vast and complex topology of the internet.

The other options do not accurately reflect the primary function of BGP. Data encryption pertains to securing data, which is not BGP's role. Facilitating file transfers relates more to application-layer protocols rather than BGP's routing functionalities. Access control in local area networks is managed by different protocols and is outside BGP's scope since BGP operates at a much larger scale, specifically between autonomous systems instead of within local networks.