To achieve accuracies in the low milliseconds over paths spanning major portions of the Internet of today, these intricate algorithms, or their functional equivalents, are necessary. However, in many cases accuracies in the order of significant fractions of a second are acceptable. In such cases, simpler protocols such as the Time Protocol, have been used for this purpose. These protocols
SNTP has been described by Network Working Group in their Request for Comments: 1305 specifications. It is a simplified version of Network Time Protocol for servers and clients. It is particularly useful for the client and server machines which were using NTP version 3 to shift over internet and World Wide Web. SNTP is designed to operate in a dedicated server configuration including an integrated radio clock. SNTP protocols can be used to fetch time from NTP server to synchronize client subnet machines. They can not be used to synchronize time between their peer client machines of the network.
The first reply received by the SNTP client is used for subsequent unicast requests from designated server and client stops responding to other server replies. Other than the selection of address in the request, the operations of anycast and unicast clients are identical.
Requests are normally sent at intervals from 64 s to 1024 s, depending on the frequency tolerance of the client clock and the required accuracy. A unicast or anycast client initializes the NTP message header, sends the request to the server and strips the time of day from the
Transmit Timestamp field of the reply. For this purpose, all of the NTP header fields shown above can be set to 0, except the first octet and (optional) Transmit Timestamp fields. In the first octet, the LI field is set to 0 (no warning) and the Mode field is set to 3 (client). The VN field must agree with the version number of the NTP/SNTP server; however, Version 4 servers will also accept previous versions. Version 3 (RFC-1305) and Version 2 (RFC-1119) servers already accept all previous versions, including Version 1 (RFC-1059).
As different versions of NTP and SNTP servers are deployed over the Internet, designing a NTP or SNTP clients should be given proper attention to maintain interoperability. It could be better practice to use latest versions of NTP/SNTP clients