Abstract:

The Internet is an integral part of nearly all aspects of modern life, and Internet Service Provider (ISP) backbone networks play an integral part in our Internet experience. Therefore, ISPs must design their networks to limit congestion and also to limit the disruptions caused by component failures. One obvious way to ensure that there's no congestion, even when switches or links fail, is to dramatically over provision the network. If the ISP builds, e.g., two redundant links for every link it actually needs, that network will probably not get too congested or disturbed by failures. But, buying all this equipment is prohibitively costly for the ISP. In this talk we explore how the ISP can optimally balance its objective of carrying all offered traffic with minimal congestion, even in the presence of failures, with its objective of minimizing costs.

The question is complicated because the ISP makes some decisions, like purchasing and placing equipment, on long timescales (months or years), and some decisions, like exactly how to route packets from a given flow, on short timescales (seconds). We classify the long timescale decisions as network design and the short timescale decisions as network operation. These decisions interact such that the ISP must consider both of them simultaneously if it wants to make a decision about either one. Accounting for failures only complicates the situation further.

In the first part of this talk, we focus on the network design problem, leveraging modern optical equipment's reconfigurability to design a minimal cost network that can still carry all traffic, even if components fail. Although this part of the talk focuses on network design, we also address network operation, since the two are interdependent. Our solution allows ISPs to save up to 29% off the cost of their network infrastructure.

In the second part of this talk we shift our focus to network operation. We propose a failure recovery protocol that allows for faster responses to failures than the approaches currently employed by ISPs. Our insight here is that this improved

network operation approach is possible if ISPs take into account the heterogenous nature of the switches they have deployed when designing their networks. Hence, although this part of the talk focuses on network operation, it, too, addresses network design.