Network Time Protocol (NTP) is a protocol for synchronizing device clocks across TCP-based computer networks. The latest documented version is NTP v3, defined in IETF RFC 1305. NTP uses UDP port 123 for the distribution of Coordinated Universal Time (UTC) in a hierarchical tree structure. Clocks are synchronized based on their Stratum level, which indicates their precision. Stratum 0 clocks refer to devices that keep highly accurate time, such as atomic clocks. Stratum 1 clocks refer to computers that receive time directly from stratum 0 clocks. Stratum 2 clocks refer to computers that receive time from Stratum 1 computers, and so forth. Network administrators typically synchronize the clocks of network infrastructure devices to synchronize timestamps of event logs collected from routers and switches through SYSLOG and SNMP Traps.
Cisco TelePresence endpoints (CTS devices, CTS-MAN, and the CTMS) all support NTP for time synchronization, which is necessary within a TelePresence deployment for scheduling the resources for a meeting. Further, time must also be synchronized with any email and calendaring systems, such as Microsoft Exchange or IBM/Lotus Domino, used to schedule meetings. Finally, it should be noted that Cisco TelePresence deployments also rely on the use of digital certificates for secure communication; such as Secure Shell (SSH) and Hypertext Transer Protocol over Secure Socket Layer (HTTPS) for secure management, and Transport Layer Security (TLS) for secure SIP signaling. These security protocols often rely on the use of digital certificates, which have a range of dates for which the certificate is valid. Therefore, to prevent any issues with these security protocols due to incorrect dates configured within TelePresence equipment, time synchronization through mechanisms such as NTP are recommended.
