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University of Cambridge Computer Laboratory
Thursday Apr 12th, 2007 - 4.30pm
Computer Laboratory > Research > Systems Research Group > NetOS > Seminars > Thursday Apr 12th, 2007 - 4.30pm

Two Days in the Life of the DNS Anycast Root Servers

Nevil Brownlee

The DNS root nameservers routinely use anycast in order to improve their service to clients and increase their resilience against various types of failures. We study DNS traffic collected over a two-day period in January 2006 at anycast instances for the C, F and K root nameservers. We analyze how anycast DNS service affects the worldwide population of Internet users.

To determine whether clients actually use the instance closest to them, we examine client locations for each root instance, and the geographic distances between a server and its clients. We find that frequently the choice, which is entirely determined by BGP routing, is not the geographically closest one.

We also consider specific AS paths and investigate some cases where local instances have a higher than usual proportion of non-local clients. We conclude that overall, anycast roots significantly localize DNS traffic, thereby improving DNS service to clients worldwide.

CAIDA have been working on a visualisation for the anycast instances, producing a 'centre of influence' plot; this will be presented and discussed.


Nevil Brownlee is an Associate Professor of Computer Science at The University of Auckland, New Zealand, and has been closely involved with CAIDA (Cooperative Association for Internet Data Analysis) since 2000. As well, he is co-chair of the IETF's IP Flow Information Export (IPFIX) Working Group.