1、QUESTION ITU-R 238/7*Trusted time source for time stamp authority (2001) The ITU Radiocommunication Assembly, considering a) that the importance of time stamping is increasing due to global development of electronic commerce; b) that the time provided from Trusted Third Party (TTP) used for time sta
2、mping service needs to be coordinated all over the world; c) that time provided from TTP needs to use a clock of very high reliability, availability and trustworthiness, as contained in ITU-T Recommendation X.842; d) that transfer of time and frequency information by digital telecommunication networ
3、ks as described in Opinion ITU-R 94 could be techniques used in timing provided by TTPs; e) that a Time Stamp Authority (TSA) is a TTP that produces the time which satisfies the condition mentioned above; f) that Coordinated Universal Time (UTC) determined by Bureau International des Poids et Mesure
4、s (BIPM) and International Earth Rotation Service (IERS) as described in Recommendation ITU-R TF.486 is the international time reference; g) that each UTC(k) generated by timing centres can be used in real time and a time difference with UTC is regularly published by the BIPM, decides that the follo
5、wing Question should be studied 1 For each timing centre, what means are appropriate in order to provide certified UTC(k) time to the TSA? 2 What are the methods for TSA to achieve the above certified time at the required accuracies? further decides 1 that the results of the above studies should be included in (a) Recommendation(s); 2 that the above studies should be completed by 2011. _ *In the year 2009, Radiocommunication Study Group 7 extended the completion date of studies for this Question.
