Today’s Internet operation is based on some characteristics of the communication links that are commonly regarded as generally available: the links’ delay, error rate and packet loss parameters are within sensible limits. Such characteristics are: the paths are end-to-end bidirectional and generally connected permanently (no permanent disruptions are expected), round-trip times do not exceed some seconds even if traveling around the the planet, error and loss rates are relatively low. TCP/IP protocols were designed based on these implicit assumptions. Design and implementation of communication in basically different environment, e. g. in deep space or between intermittently available (flying) devices requires a different kind of protocols with modified principles. Deep space environment is characterized by intermittent connectivity, extremely long delay and high error rates. Delay- and Disruption-Tolerant Networking (DTN) addresses these issues by redesigning the protocol stack such as introducing the Bundle Protocol which utilizes store-and-forward message switching. DTN nodes have persistent storage and they are optionally capable of custody transfer. Although packet switching principle is kept, transfer responsibility is handled hop-by-hop which is different from TCP/IP’s end-to-end nature. The Bundle Protocol operates in Layer 5 and uses endpoint IDs for addressing purposes which are not tied to physical location. We discuss the new potential Layer 3 and Layer 4 protocols and their relation to Bundle Protocol.