In mobile agent research, agent-to-agent (A2A) communication often relies on an infrastructure of the discovery sever to resolve the location of the agents. This not only induces overhead on managing, maintaining and deploying these discovery servers, but also complicates the development of agent applications. While considering scalability and reliability, such an agent discovery infrastructure becomes very sophisticated. In this paper, we propose a novel A2A communication system, called Armada, which is autonomic and it does not require a discovery infrastructure. Armada is scalable and reliable, and suitable for a wide-area environment with dynamic entities. It does not pose mobile constrains to the agents. Each agent can be globally and uniquely identified without regarding its location. We evaluate Armada through large-scale simulation and prototype measurement in a cluster environment with 35-node desktop PCs. Results from both accesses presents an efficient design of Armada.