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Two-way satellite time and frequency transfer (TWSTFT)[1] has been developed into a widely used technique of time and frequency transfer between laboratories that contribute, with their atomic clocks and, in some cases, with their primary frequency standards, to the realization of International Atomic Time (Temps Atomique International, TAI)[2]. The TWSTFT technique is thus used in two areas: for true time transfer, by comparing local time scales such as local realizations of Coordinated Universal Time (UTC (i)) in laboratories i, and for accurate frequency comparisons between atomic fountain clocks and hydrogen masers. At present, TWSTFT is performed operationally in at least two laboratories in the United States, twelve in Europe, and seven in the Asia Pacific region. The cooperation is organized by the CCTF Working Group on TWSTFT. For each of the regional networks, an administrator has been assigned who should be contacted before changes to the operational practice are made or when a new institute wishes to join. At the time of writing the regional administrators are Miho Fujieda (NICT) and Dirk Piester (PTB).