TR-07-9.pdf
``Maintaining strong cache consistency for the Domain Name System"
Xin Chen, Haining Wang, Shansi Ren, and Xiaodong Zhang
IEEE Transactions on Knowledge and Data Engineering, Vol. 19, No. 8,
2007, pp. 1057-1071.
Abstract
Effective caching in the Domain Name System (DNS) is critical to its
performance and scalability. Existing DNS only supports weak cache
consistency by using the Time-to-Live (TTL) mechanism, which functions
reasonably well in normal situations. However, maintaining strong cache
consistency in DNS as an indispensable exceptional handling mechanism has
become more and more demanding for three important objectives: 1) to
quickly respond and handle exceptions such as sudden and dramatic Internet
failures caused by natural and human disasters, 2) to adapt increasingly
frequent changes of Internet Protocol (IP) addresses due to the introduction
of dynamic DNS techniques for various stationed and mobile devices on the
Internet, and 3) to provide fine-grain controls for content delivery services
to timely balance server load distributions. With agile adaptation to various
exceptional Internet dynamics, strong DNS cache consistency improves the
availability and reliability of Internet services. In this paper, we first
conduct extensive Internet measurements to quantitatively characterize DNS
dynamics. Then, we propose a proactive DNS cache update protocol (DNScup),
running as middleware in DNS name servers, to provide strong cache
consistency for DNS. The core of DNScup is an optimal lease scheme, called
dynamic lease, to keep track of the local DNS name servers. We compare
dynamic lease with other existing lease schemes through theoretical
analysis and trace-driven simulations. Based on the DNS Dynamic Update
protocol, we build a DNScup prototype with minor modifications to the
current DNS implementation. Our system prototype demonstrates the
effectiveness of DNScup and its easy and incremental deployment on
the Internet.