``DNScup: a strong cache consistency protocol for DNS"

Xin Chen, Haining Wang, Shansi Ren, and Xiaodong Zhang

Proceedings of the 26th International Conference on Distributed
Computing Systems (ICDCS'06), Lisbon, Portugal, July 4-7, 2006.

Abstract

Effective caching in 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 exceptional incidents, such as sudden and
dramatic Internet failures caused by natural and human disasters, (2) to
adapt increasingly frequent changes of 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 propose a proactive DNS cache
update protocol, called DNScup, running as middleware in DNS
nameservers, to provide strong cache consistency for DNS. The core of
DNScup is a dynamic lease technique to keep track of the local DNS
nameservers, whose clients need cache coherence to avoid losing service
availability. Based on the DNS Dynamic Update protocol, we have built a
DNScup prototype with minor modifications to the current DNS
implementation. Our trace-driven simulation and system prototype
demonstrate the effectiveness of DNScup and its easy and incremental
deployment on the Internet.