In Domain Name System (DNS), 13 root servers are deployed in order to provide top-level domain name resolution service and they are denoted by 13 letters. From year 2000 or so, the anycast technology has been adopted to extend the number of root servers with the explosive expansions of global Internet. To date, 11 of the 13 letters are hosted at multiple sites, and the root zone is served at about 400 sites around the world. In this paper, the issues of current DNS root server deployment are analyzed and two schemes to scale the number of root servers are discussed. From the analysis, we find that the unbalanced deployment of 13 root servers results in serious root zone file distribution latency and Border Gateway Protocol (BGP) convergence cost. For the two schemes proposed, the hierarchical deployment of global/local anycast sites is an efficient short-term solution, while increasing the root servers furthermore and geographically distributing them all around the world is a forethoughtful solution.
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