he Use of Persistent Identifiers To use the framework, users are expected to be able to manage their own handles. The Handle System provides a free administration tool [10] for this purpose. This tool is currently implemented in JAVA. Currently, users wishing to associate with a proxy server are required to specify the latter's IP address or domain name. Since our approach exploits handles instead of domain names, we have implemented a specialized gateway that translates between DNS and handle protocols. The gateway is responsible for protocol translation, specifically, handle to DNS. We refer to this gateway as the Handle-DNS proxy (HDP). HDP is a modified DNS server that commu- nicates using the BIND protocol and implements extra functionality, allowing it to associate canonical names and aliases inside its particular naming zone with handles. HDP will, therefore, resolve canonical names inside its naming zone using the Handle System and will, in addition, allow any common DNS server to resolve DNS entries in the format: <handle> [DNS proxy domain] to the actual value of the SIP HOST attribute of that particular handle. Details about this gateway, which can be extended to become a plug-in for current DNS servers, are presented in [32]. The ease of deployment of our framework and success of the conducted experiments encourage us to pursue this work. 10.4.2 Experimental Model In this section, we will compare the performance of roaming and non-roaming environments in terms of registration and call establishment delays. The non- roaming case represents traditional SIP signaling between a user and his home SIP server irrespective of roaming, while the former case represents our pro- posed approach. Both cases were tested under the same conditions regarding UA/SIP processor speed and workloads. As UA, we used the Java SIP Com- municator [38]. We also tested with the Cisco 7940/7960 IP phones. 10.4.2.1 Registration Figure 10.5 is a magnified image of Figure 10.2 that focuses on the registration process according to th