Which VPN provides scalability for organizations with many remote sites?

DMVPN (Dynamic Multipoint VPN) is designed for large-scale deployments with many remote sites because it allows spokes to dynamically build IPsec tunnels directly with each other (spoke-to-spoke) without needing to traverse a central hub, significantly reducing the configuration complexity and improving scalability.

SSL VPNs are typically used for remote access by individual users (client-to-site) and are less suited for connecting many remote sites together in a mesh or hub-and-spoke architecture.

GRE over IPsec provides secure tunneling but still requires static configuration of each tunnel endpoint, making it less scalable than DMVPN for a large number of dynamic remote sites.

Site-to-site IPsec VPNs typically require static configuration of tunnels between each pair of sites, which becomes unmanageable and unscalable for organizations with many remote locations (N^2 complexity in a full mesh).