  The emerging paradigm of network function virtualization advocates deploying
virtualized network functions (VNF) on standard virtualization platforms for
significant cost reduction and management flexibility. There have been system
designs for managing dynamic deployment and scaling of VNF service chains
within one cloud data center. Many real-world network services involve
geo-distributed service chains, with prominent examples of mobile core networks
and IMSs (IP Multimedia Subsystems). Virtualizing these service chains requires
efficient coordination of VNF deployment across different geo-distributed data
centers over time, calling for new management system design. This paper designs
a dynamic scaling system for geo-distributed VNF service chains, using the case
of an IMS. IMSs are widely used subsystems for delivering multimedia services
among mobile users in a 3G/4G network, whose virtualization has been broadly
advocated in the industry for reducing cost, improving network usage efficiency
and enabling dynamic network topology reconfiguration for performance
optimization. Our scaling system design caters to key control-plane and
data-plane service chains in an IMS, combining proactive and reactive
approaches for timely, cost-effective scaling of the service chains. We
evaluate our system design using real-world experiments on both emulated
platforms and geo-distributed clouds.
