Evolution of functional core in network-related function calls during Linux kernel development

Abstract

Recently, network function virtualization has been focused on achieving a flexible deployment of networking services. Despite the fact that the heart of network function virtualization is its software implementation, there are fewer studies on how network functions are implemented as software. In this study, we investigate the evolution of functional connectivity in network functions using an implementation of Internet protocol suite in the Linux kernel. We constructed a call graph for the Linux kernel and analyzed the change of connectivity between the protocol components based on the directory structure of Linux kernel. Our results on the connectivity analysis show that new sub-directories appears for new emerging technologies, such as “bluetooth” and “sctp”, and they rely mostly on the function of sub-directories “core” and “ipv4”. Since the number of functions in sub-directories “core” and “ipv4” is increasing, we defined a functional core for the call graph to see whether there is a core part which has lower variability during the kernel development or not. The result shows that the functional core consists of mostly 50-70 functions and has lower variability comparing with the increase of a number of network-related functions during the kernel development.