CS364A: Algorithmic Game Theory Lecture #12: More on Selsh Routing

The selfish routing model introduced last lecture can provide insight into many different kinds of networks, including transportation, communication, and electrical networks. One big advantage in communication networks is that it’s often relatively cheap to add additional capacity to a network. Because of this, a popular strategy to communication network management is to install more capacity than is needed, meaning that the network will generally not be close to fully utilized (see e.g. [4]). There are several reasons why network over-provisioning is common in communication networks. One reason is to anticipate future growth in demand. Beyond this, it has been observed empirically that networks tend to perform better — for example, suffering fewer packet drops and delays — when they have extra capacity. Network over-provisioning has been used as an alternative to directly enforcing “quality-of-service (QoS)” guarantees (e.g., delay bounds), for example via an admission control protocol that refuses entry to new traffic when too much congestion would result [4]. The goal of this section is develop theory to corroborate the empirical observation that network over-provisioning leads to good performance. Section 1.2 shows how to apply directly the theory developed last lecture to over-provisioned networks. Section 1.3 offers a second approach to proving the same point, that selfish routing with extra capacity is competitive with optimal routing.