Man-In-the-Middle Anycast (MIMA): CDN User-Server Assignment Becomes Flexible

Abstract

Within Content Delivery Networks (CDNs), users are typically geographically load-balanced across multiple servers in order to provide better performance and locality - users are assigned to the content servers close to them. One approach to user-server assignment is the use of IP anycast, where all the content servers use the same IP address. A user request is then routed to the server closest to the user, determined by the routing protocols such as BGP. However, there are problems associated with this anycast-based approach. IP anycast is generally incapable of updating or redirecting users to a different (better) server without breaking already established TCP sessions. Moreover, the CDN operators do not have much control on where to redirect the users - it is completely controlled by Internet routing. In this paper we present our Man-In-the-Middle Anycast (MIMA) architecture, a novel anycast-based design that leverages Network Functions Virtualization (NFV) and Software Defined Networking (SDN) techniques to enable flexible and efficient user-server assignment. We demonstrate that the MIMA architecture is capable of performing flexible user-server assignment and offloading during times of high demand, such as flash crowd events that are becoming more common in a media-focused Internet. These capabilities offered by MIMA provide CDN operators a higher degree of flexibility in network management and content provisioning by enabling flexible user-server assignment.