 network analysis tools are used in the network, then a malicious third parry can track the locations, using the caller's address-of-record fields. In such a case it could link address-of-records to physical locations, using data mining techniques, and finally with people, since there would be only a few people that make phone calls from particular residential addresses during a day. So, the question is: is total anonymity possible in SIP, and how could this be applied to shield the identity, or the character of a dog or a human? 20.2 Motivation According to Justice Louis Brandeis, the right to privacy is "the right to be left alone"t. Additionally, Alan Westin identifies privacy as "the desire of people to choose freely under what circumstances and to what extent they will expose themselves, their attitude and their behavior to others"+ Nowadays, we can define privacy in different domains, not vertical, but overlapped: Physical privacy-such as DNA searching. Information privacy-the unsanctioned invasion of privacy by the gov- ernment, corporations or individuals in order to identify, or even handle, our personal information such as our age, address, market profiles, daily communications, or even sexual preference. Context privacy-each individual's fundamental right not to be linked with places, people, locations and preferences in his daily life because of surveillance cameras, sensor networks and RFID systems. +L. Brandeis, S. Warren. 1890. A. Westin. 1967. C 2009 by Taylor & Francis Group, LLC Anonymity in SIP Privacy is sometimes related to anonymity. According to Rana and Sharma [1] and the Oxford English Dictionary, anonymity is defined as "the state of being anonymous" which in turn is described as "nameless, having no name; of unknown name". This definition is vague, since in real-world implemen- tations it should be clear which identity should be hidden and from whom. To better define anonymity, Pfitzmann and Kohntopp introduced the most common definition of anonymity used in the information and informat