In network computing offers an appealing scalability trajectory for network services, as application performance scales with network devices. Despite its potential, in-network computing may not be suitable for all applications, both due to paradigm assumptions and network-device limitations. As the users' demands from the Internet keep growing, any limitations on the scalability of network services such as DNS limits the scalability of end-to-end experience. In this paper we present P4DNS, an in-network DNS solution, exploring the span and limitations of implementing a realistic network service within a network device. P4DNS is a high performance DNS server, implemented in P4->NetFPGA and providing performance improvement compared with software-based solutions. We discuss the limitations of implementing in-network services using today's paradigms and the trade-offs between data and control planes