VentureBeat
Follow
MCP solved tool calling. A2A solved coordination. What solves transport?
Distributed computing saw protocol proliferation before consolidation, with REST, MQTT, and WebSockets emerging as dominant. The AI agent ecosystem is now in a similar proliferation phase, with four key protocols published recently: MCP, ACP, A2A, and ANP. These protocols address different layers of the communication stack rather than directly competing. MCP is for tool-calling, A2A handles task coordination, ACP is for lightweight message envelopes, and ANP focuses on discovery and identity. This creates a complementary stack for agent communication.
However, a significant challenge remains in the transport layer, as current HTTP-based protocols assume reachable servers, which is problematic for devices behind NAT. This forces messages through costly and latent relay infrastructure. While technologies for peer-to-peer connectivity exist, such as UDP hole-punching and QUIC, the agent context requires capability-based routing—finding peers by their functions, not just their addresses. Pilot Protocol and libp2p are actively addressing this transport problem.
The application-layer protocols (MCP, A2A) are nearing stable versions, with future work focusing on hardening and federation. The transport layer is 18-24 months behind, expecting initial diversity followed by consolidation around effective implementations. Standardization from IETF and W3C is anticipated around 2027-2028, likely preceded by de facto open-source standards. For current architecture decisions, adopting stable application-layer protocols like MCP is low-risk, while the transport layer requires cautious evaluation of early implementations or custom development. A clean separation between application semantics and transport layers is crucial now to facilitate future transitions to stable transport solutions.
