Abstract: We revisit the problem of connection management for reliable transport as part of our clean-slate Recursive InterNet Architecture (RINA). At one extreme, a pure soft-state (SS) approach (as in Delta-t) safely removes the state of a connection at the sender and receiver once the state timers expire without the need for explicit removal messages. And new connections are established without an explicit handshaking phase. On the other hand, a hybrid hard-state/soft-state (HS+SS) approach (as in TCP) uses both explicit handshaking as well as more limited timer-based management of the connection’s state.
In this paper, we consider the worst-case scenario of reliable single-message communication. Using simulation, we evaluate various approaches in terms of correctness (with respect to data loss and duplication) and robustness to bad network conditions (high message loss rate and variable channel delays). Our results show that the SS approach is more robust, and has lower message overhead and higher goodput. Thus, SS presents the best choice for reliable applications, especially those operating over bandwidth-constrained, error-prone networks. This result also suggests that within a clean-slate transport architecture, explicit
connection messages for data reliability are not needed, and so a simple common packet interface based on Delta-t—rather than TCP vs. T/TCP vs. UDP, etc.— can be provided to support both transactional and bulk, reliable and unreliable (unacknowledged) applications.