``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.