Serval: An End-Host Stack for Service-Centric Networking

Abstract

Internet services run on multiple servers in different locations, serving clients that are often mobile and multi-homed. This does not match well with today’s network stack, designed for communication between fixed hosts with topology-dependent addresses. As a result, on-line service providers resort to clumsy and management-intensive work-arounds—forfeiting the scalability of hierarchical addressing to support virtual server migration, directing all client traffic through dedicated load balancers, restarting connections when hosts move, and so on.

In this paper, we revisit the design of the network stack to meet the needs of online services. The centerpiece of our Serval architecture is a new Service Access Layer (SAL) that sits above an unmodified network layer, and enables applications to communicate directly on service names. The SAL provides a clean service-level control/data plane split, enabling policy, control, and in-stack name-based routing that connects clients to services via diverse discovery techniques. By tying active sockets to the control plane, applications trigger updates to service routing state upon invoking socket calls, ensuring up-to-date service resolution. With Serval, end-points can seamlessly change network addresses, migrate flows across interfaces, or establish additional flows for efficient and uninterrupted service access. Experiments with our high-performance in-kernel prototype, and several example applications, demonstrate the value of a unified networking solution for online services.