For financial markets, the ability to verify continuously when events take place, i.e., time traceability, is fundamental to enable regulatory oversight and analyse the order in which trades are placed (e.g. accurate time stamps are used to settle disagreements and to prevent fraud). Market participants may execute orders on stocks in seconds or microseconds depending on the type of trading activity (e.g., high-frequency algorithmic, voice trading systems, human intervention, concluding negotiated transactions, etc). Financial markets are distributed systems; therefore, a common regulated timekeeping system can only be done if every market participant at each end point of the system involved in the transaction maintains an accurate clock.
There are several means to access UTC time such as using an atomic clock, NTP servers, GNSS signal, or UTC(k) delivery over fiber, where UTC(k) is a realisation of UTC maintained by the contributing institute (e.g., NPL, NIST) identified by k. The 5G system can be operate in collaboration with or as backup to other timing solutions used already by financial markets to comply with financial directives for timekeeping. As illustrated in Figure 4.2-1
, the 5G system can be integrated as another time source within the clock distribution infrastructure of the financial customer.
Financial regulations for time source and time dissemination require the market participants must provide traceability back to UTC. This requires the time information sent to financial exchanges should be measured and verified at every link in the chain, i.e. from UTC generated at the BIPM (global 'paper' time scale 
) up to the timestamping engine within the financial customer domain. Depending on the time source and distribution method the financial customer has, the traceability to UTC to comply with the regulations is achieved in different ways. For example (for more information see 
If GNSS satellite signals are used, these signals alone do not readily provide traceability to UTC, but users can demonstrate traceability by obtaining GNSS monitoring bulletins from one of the regional UTC(k) timing centres. In this case, the end user will use these bulletins in addition to perform calibration and monitoring of the GNSS receiver equipment to demonstrate traceability to UTC.
If services for time delivery over fibers are used (e.g., as delivered by a national metrology institutes), the UTC is disseminated over managed fiber links. The traceability to UTC is maintained using PTP to distribute the time and continuously monitoring and audit the provision point to ensure the agreed level of accuracy defined in the service SLA. Note: this option may not be generally available.
The 5G system could follow similar approaches when applied in this use case (Figure 4.2-2
illustrates the two approaches):
The 5G system provides traceability to UTC up to the DS-TT: In this approach, the 5G system needs to continuously monitor and audit each link within the time distribution chain within the 5G system domain. The UTC traceability is certified up to the provision point at the DS-TT. Therefore, monitoring, calibration, and certification functionalities are required at the DS-TT. Two alternatives can be considered:
The 5G system supports these new functionalities including the required mechanisms in the standard.
Proprietary solutions are used in collaboration with the 5G system. For example, a client for the service of time delivery over fiber is installed within the DS-TT to combine NPL service and 5G wireless time distribution to provide traceability to UTC.
The 5G system does not provide traceability to UTC: Similar to GNSS signal delivery described before, the 5G system is not responsible of monitoring, calibrating or documenting evidence for traceability to UTC, the financial customer is taking care of these functionalities.