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Performance - Load Imbalance

DNS measurements at root and TLD nameservers show that they handle a large load and are frequently subjected to denial of service attacks [4,5]. A massive distributed DoS attack [28] in November 2002 rendered nine of the thirteen root servers unresponsive. Partly as a result of this attack, the root is now served by more than sixty nameservers and is served through special-case support for BGP-level anycast. While this approach fixes the superficial problem at the topmost level, the static DNS hierarchy fundamentally implies greater load at the higher levels than the leaves. The special-case handling does not provide automatic replication of the hot spots, and sustained growth in client population will require continued future expansions. In addition to creating exploitable vulnerabilities, load imbalance poses performance problems, especially for lookups higher in the name hierarchy.