connected to the GNSS receiver and provides precision timing protocol (PTP) packets over the IP/Ethernet interface toward the transmission network. The grandmaster clock is able to maintain timing even during quite long GPS jamming. The boundary clock is a network element which consists of both master and slave functionalities. At the slave side, it receives a PTP packet from the grandmaster or another boundary clock and terminate the PTP protocol and tries to estimate the correct time from the master. At the master side, a new PTP packet is created based on the timing information of the boundary clock and sent out to the next boundary clock in the chain or slave. In short, each boundary clock tries to obtain the accurate time information from the master and pass it to the next boundary clock/slave in the chain. Boundary clock functionality can be integrated into the switch or router in the transmission network. The transparent clock is a network element that transparently forwards the PTP packet it receives from one port to another without terminating the PTP session. The transparent clock, however, adds residence delay (i.e. the duration of the PTP packets residence in the transparent clock) to the PTP packets SO that the next slave in the chain can use this information to calculate the correct time. Transparent clock functionality can be integrated into the switch or router in the transmission network. The slave is a network element that terminates the PTP protocol and tries to estimate the correct time from the master. A BTS is a network element that consists of both slave functionality and the end application. An end application takes the final time information from the slave for its usage. Full on-path support - every transmission hop between the grandmaster and slave (BTS) must be equipped with either boundary clock functionality or transparent clock functionality. Partial on-path support - Some of the transmission hops between the grandmaster and slave (BTS) can be equipped with boundary clock functionali