Seamless BGP Migration with Router Grafting

Network operators are under tremendous pressure to make their networks highly reliable to avoid service disruptions. Yet, operators often need to change the network to upgrade faulty equipment, deploy new services, and install new routers. Unfortunately, changes cause disruptions, forcing a trade-off between the benefit of the change and the disruption it will cause. In this paper we present router grafting, where parts of a router are seamlessly removed from one router and merged into another. We focus on grafting a BGP session and the underlying link–from one router to another, or between blades in a cluster-based router. Router grafting allows an operator to rehome a customer with no disruption, compared to downtimes today measured in minutes. In addition, grafting a BGP session can help in balancing load between routers or blades, planned maintenance, and even traffic management. We show that grafting a BGP session is practical even with today’s monolithic router software. Our prototype implementation uses and extends Click, the Linux kernel, and Quagga, and introduces a daemon that automates the migration process.