1. Measuring Large Overlay Networks — The Overnet Example
2. As URLs include domain names, a document's URL has to be changed if it is moved to another computer with a different domain name. To solve this problem of ever changing URLs, URNs create a location-independent namespace on top of the URL namespace. For more information, see;Leslie L Daigle;On the World Wide Web, Web pages are identified by URLs,1997
3. For an overview of all registered URN namespaces, see IANA, URN Namespaces;Karen Sollins;Request for Comments (RFC),1994
4. DNA sequence namespaces, for example, do not prevent higher-level namespaces from being built on top of them. See Birney et al., supra note 162. 242. See Michael Gowan;How it Works: Instant Messaging,2000