Abstract. We describe some of the issues in the design of a new packet switched network protocol. Adaptation to various network technologies along the dimensions of speed, error model, robustness, etc., is a goal for this new proto col. We look at the adaption in size of the pack et header to the speed and robustness of the underlying network to allow efficient communication on low-speed wireless networks, for example. We also explore issues in resource reservation and multicast for real-time multimedia, the notion of a network "flow", a hybrid of datagrams and virtual circuits, and suggest common solutions for both mobile and multicast routing. The authors are engaged in the design of a network protocol, NP++, whose goal is flexibility over a wide dynamic range of speeds and varying kinds of hardware switching elements.