The study has several limitations. First, the measurement machines used in the study are limited both in number and models. Six machines have been used for measurement purpose and only two of them could serve as dedicated measurement machines. All the machines are IBM PC compatible with Intel CPUs. Second, the operating system platform used is limited to Linux. Third, the Internet hosts to which ping packets have been sent are limited both in number and areas. Only 148 hosts have been pinged and most of them are inside New Zealand.