DMVPN Phase 3 hub-and-spoke is the best design for this requirement. The customer wants secure dynamic site-to-site VPN connectivity for voice, video, and FTP, and also wants branches to communicate directly instead of hairpinning all traffic through headquarters. DMVPN supports dynamic spoke-to-spoke tunnels using multipoint GRE, NHRP, and IPsec protection. Phase 3 is more scalable than Phase 2 because the hub can send NHRP redirect messages and spokes can install shortcut routes, reducing the need for every spoke to maintain detailed next-hop information for every other spoke. That is important because the branch routers have limited memory. Phase 1 is hub-and-spoke only and does not provide dynamic spoke-to-spoke forwarding. A hierarchical Phase 3 design can be useful at very large scale, but the question describes a headquarters and remote branch design rather than multiple tiers of hubs. Phase 3 hub-and-spoke satisfies direct branch communication, security, and scale. Reference topics: DMVPN Phase 3, NHRP redirect, spoke-to-spoke tunnels, IPsec encryption, branch WAN scalability.