On the one hand network and communication protocols are complex and difficult to design, on the other hand it is important that network systems are robust and reliable. Thus it is desirable to have formal models augmented with tools that support simulation and testing that can be used by designers of new protocols, both in the early stages of design, as well as in later stages, where more rigorous formal analysis is important. In this paper we present the specification of a network model in the rewriting logic language Maude along with some primitives for defining simulation strategies. The use of the model is illustrated with a simple HELLO sub-protocol taken from the IETF PIM-DM (Protocol Independent Multi-Cast-Dense Mode) The network model we present reflects the key aspects of the infra-structure on which typical communication protocols run. The model is designed so that we may execute isolated protocols as well as develop techniques for composing sub-protocols, to model the more complex protocols used in practice. The long term goal is to support simulation and formal analysis at many levels of detail.