John Heidemann

Anycast vs. DDoS: Evaluating the November 2015 Root DNS Event

TitleAnycast vs. DDoS: Evaluating the November 2015 Root DNS Event
Publication TypeConference Paper
Year of Publication2016
AuthorsG. C. M. Moura, R. O. de Schmidt, J. Heidemann, W. B. de Vries, M. Müller, L. Wei, and C. Hesselman
Conference NameProceedings of the ACM Internet Measurement Conference

Distributed Denial-of-Service (DDoS) attacks continue to be a major threat on the Internet today. DDoS attacks overwhelm target services with requests or other traffic, causing requests from legitimate users to be shut out. A common defense against DDoS is to replicate a service in multiple physical locations/sites. If all sites announce a common prefix, BGP will associate users around the Internet with a nearby site, defining the \emphcatchment of that site. Anycast defends against DDoS both by increasing aggregate capacity across many sites, and allowing each site's catchment to contain attack traffic, leaving other sites unaffected. IP anycast is widely used by commercial CDNs and for essential infrastructure such as DNS, but there is little evaluation of anycast under stress. This paper provides the \emphfirst evaluation of several IP anycast services under stress with public data. Our subject is the Internet's Root Domain Name Service, made up of 13 independently designed services (``letters'', 11 with IP anycast) running at more than 500 sites. Many of these services were stressed by sustained traffic at $100\times$ normal load on Nov. 30 and Dec. 1, 2015. We use public data for most of our analysis to examine how different services respond to stress, and identify two policies: sites may \emphabsorb attack traffic, containing the damage but reducing service to some users, or they may \emphwithdraw routes to shift both good and bad traffic to other sites. We study how these deployment policies resulted in different levels of service to different users during the events. We also show evidence of \emphcollateral damage on other services located near the attacks.