Policy-compliant Path Research Articles

Synthesis of Fault-Tolerant Distributed Router Configurations

Operators of modern networks require support for diverse and complex end-to-end policies, such as, middlebox traversals, isolation, and traffic engineering. While Software-defined Networking (SDN) provides centralized custom routing functionality in networks to realize these policies, many networks still deploy "legacy" control planes running distributed routing protocols like OSPF and BGP because these protocols are scalable and robust to failures. However, realization of policies by distributed control plane configurations is manual and error-prone. We present Zeppelin, a system for automatically generating policy-compliant control planes that also behave well under majority of small network failures. Zeppelin differs from existing approaches in that it uses policy-compliant paths to guide the synthesis process instead of directly generating policy-compliant configurations. We show that Zeppelin synthesizes highly resilient and policy-compliant configurations for real topologies with up to 80 routers.

Synthesis of Fault-Tolerant Distributed Router Configurations

Operators of modern networks require support for diverse and complex end-to-end policies, such as, middlebox traversals, isolation, and traffic engineering. While Software-defined Networking (SDN) provides centralized custom routing functionality in networks to realize these policies, many networks still deploy "legacy" control planes running distributed routing protocols like OSPF and BGP because these protocols are scalable and robust to failures. However, realization of policies by distributed control plane configurations is manual and error-prone. We present Zeppelin, a system for automatically generating policy-compliant control planes that also behave well under majority of small network failures. Zeppelin differs from existing approaches in that it uses policy-compliant paths to guide the synthesis process instead of directly generating policy-compliant configurations. We show that Zeppelin synthesizes highly resilient and policy-compliant configurations for real topologies with up to 80 routers.

A Measurement Study on Potential Inter-Domain Routing Diversity

In response to Internet emergencies, Internet resiliency is investigated directly through an autonomous system (AS) level graph inferred from policy-compliant BGP paths or/and traceroute paths. Due to policy-driven inter-domain routing, the physical connectivity does not necessarily imply network reachability in the AS-level graph, i.e., many physical paths are not visible by the inter-domain routing protocol for connectivity recovery during Internet outages. We call the invisible connectivity at the routing layer, which can be quickly restored for recovering routing failures by simple configurations, as the potential routing diversities. In this paper, we evaluate two kinds of potential routing diversities, which are recognized as Internet eXchange Points (IXPs) participant reconnection and peering policy relaxation. Using the most complete dataset containing AS-level map and IXP participants that we can achieve, we successfully evaluate the ability of potential routing diversity for routing recovery during different kinds of Internet emergencies. Encouragingly, our experimental results show that 40% to 80% of the interrupted network pairs can be recovered on average beyond policy-compliant paths, with rich path diversities and a little traffic shifts. Thus, this paper implies that the potential routing diversities are promising venues to address Internet failures.

LIFEGUARD

The Internet was designed to always find a route if there is a policy-compliant path. However, in many cases, connectivity is disrupted despite the existence of an underlying valid path. The research community has focused on short-term outages that occur during route convergence. There has been less progress on addressing avoidable long-lasting outages. Our measurements show that long-lasting events contribute significantly to overall unavailability. To address these problems, we develop LIFEGUARD , a system for automatic failure localization and remediation. LIFEGUARD uses active measurements and a historical path atlas to locate faults, even in the presence of asymmetric paths and failures. Given the ability to locate faults, we argue that the Internet protocols should allow edge ISPs to steer traffic to them around failures, without requiring the involvement of the network causing the failure. Although the Internet does not explicitly support this functionality today, we show how to approximate it using carefully crafted BGP messages. LIFEGUARD employs a set of techniques to reroute around failures with low impact on working routes. Deploying LIFEGUARD on the Internet, we find that it can effectively route traffic around an AS without causing widespread disruption.