  The DNS relies on caching to ensure high scalability and good performance. In
optimizing caching, TTL adjustment provides a means of balancing between query
load and TTL-dependent performances such as data consistency, load balancing,
migration time, etc. To gain the desired balance, TTL adjustment depends on
predictions of query loads under alternative TTLs. This paper proposes a model
of DNS server load, which employs the uniform aggregate caching model to
simplify the complexity of modeling clients' requests and their caching. A
method of predicting DNS server load is developed using that model. The
prediction method is solely based on the unilateral measurements or
observations at authoritative servers. Without reliance on lots of multi-point
measurements nor distributed measuring facilities, the method is best suited
for DNS authoritative operators. The proposed model and prediction method are
validated through extensive simulations. Finally, global sensibility analysis
is conducted to evaluate the impacts of measurement uncertainties or errors on
the predictions.
