This document specifies the requirements for secured and unsecured diagnostic communication between client DoIP entity and server(s) installed in the vehicle using Internet protocol (IP) as well as the transmission control protocol (TCP) and user datagram protocol (UDP). This includes the definition of vehicle gateway requirements (e.g., for integration into an existing computer network) and test equipment (client DoIP entity) requirements (e.g., to detect and establish communication with a vehicle). This document specifies features that are used to detect a vehicle in a network and enable communication with the vehicle gateway as well as with its sub-components during the various vehicle states. These features are separated into two types: mandatory and optional. This document specifies the following mandatory features: — vehicle network integration (IP address assignment); — vehicle announcement and vehicle discovery; — vehicle basic status information retrieval (e.g., diagnostic power mode); — connection establishment (e.g., concurrent communication attempts), connection maintenance and vehicle gateway control; — data routing to and from the vehicle's sub-components; — error handling (e.g., physical network disconnects). This document specifies the following optional features: — DoIP entity status monitoring; — transport layer security (TLS); — DoIP entity firewall capabilities.