A Model of Internet Routing Using Semi-modules

Abstract

Abstract. Current Internet routing protocols exhibit several types of anomalies that can reduce network reliability. In order to design more robust protocols we need better formal models to capture the complexities of Internet routing. In this paper we develop an algebraic model that clarifies the distinction between routing tables and forwarding tables. We hope that this suggests new approaches to the design of routing protocols.

On the interaction of multiple routing algorithms

“…Section 6 extends the routing and forwarding model of [4] we argue that many of the design decisions made in today's RR/AD framework are reasonable. On the negative side, it seems difficult to avoid the fact that a stable forwarding solutions may depend on the details of the algorithms used (path-vector vs. link-state) by the participating protocols.…”

“…Section 3 reviews the algebraic distinction between path metrics and routing metrics recently presented in [4]. This approach echoes the idea of having distinct name spaces for infrastructure (routers) and destinations (a range of IP addresses) [5] which has recently been embodied in the Locator/ID split work [14].…”

“…We need to make this interaction explicit in a way that integrates well with an algebraic theory of routing. We adopt a solution recently proposed [4] which employs semi-modules to model this distinction.…”

“…The main idea of [4] is that the matrix of routing metrics R, such as those of Figure 5, can be described using semi-modules. Given a semiring S of path metrics, a (left) semi-module over S is a structure of the form (U, , ,0) that satisfies the axioms of Figure 7.…”

Theory and new primitives for safely connecting routing protocol instances

“…The models only apply to existing solutions, and the derived guidelines further restrict the expressiveness of the already rigid current primitives. Recently, two researchers [6] have proposed a new algebraic approach based on idempotent semirings to model routing, including the case across multiple routing instances. While the approach is general and promising, it models only route redistribution, not AD, nor the interaction of route redistribution and AD, which was left as future work.…”