One of the key infrastructure components in all telecommunication networks, ranging from the telephone network, to VC-oriented data networks, to the Internet, is its signaling system. Two broad approaches towards signaling can be identified: so-called hard-state and soft-state approaches. Despite the fundamental importance of signaling, our understanding of these approaches - their pros and cons and the circumstances in which they might best be employed - is mostly anecdotal (and occasionally religious). In this paper, we compare and contrast a variety of signaling approaches ranging from a “pure” soft state, to soft-state approaches augmented with explicit state removal and/or reliable signaling, to a “pure” hard state approach. We develop an analytic model that allows us to quantify state inconsistency in single- and multiple-hop signaling scenarios, and the “cost” (both in terms of signaling overhead, and application-specific costs resulting from state inconsistency) ...
Ping Ji, Zihui Ge, James F. Kurose, Donald F. Tows