A Scalable VPN Gateway for Multi-Tenant Cloud Services

Major cloud providers offer networks of virtual machines with private IP addresses as a service on the cloud. To isolate the address space of different customers, customers are required to tunnel their traffic to a Virtual Private Network (VPN) gateway, which is typically a middlebox inside the cloud that internally tunnels each packet to the correct destination. To improve performance, an increasing number of enterprises connect directly to the cloud provider's network at the edge, to a device we call the provider's edge (PE). PE is a chokepoint for customer's traffic to the cloud, and therefore a natural candidate for implementing network functions concerning customers' virtual networks, including the VPN gateway, to avoid a detour to middleboxes inside the cloud.

At the scale of today's cloud providers, VPN gateways need to maintain information for around a million internal tunnels. We argue that no single commodity device can handle these many tunnels while providing a high enough port density to connect to hundreds of cloud customers at the edge. Thus, in this paper, we propose a hybrid architecture for the PE, consisting of a commodity switch, connected to a commodity server which uses Data-Plane Development Kit (DPDK) for fast packet processing. This architecture enables a variety of network functions at the edge by offering the benefits of both hardware and software data planes. We implement a scalable VPN gateway on our proposed PE and show that it matches the scale requirements of today's cloud providers while processing packets close to line rate.