NTP – Network Time Protocol

Network Time Protocol provides the service of time synchronisation for all devices on the network (which have NTP service available and configured).

NTP service usually listens on UDP port 123. It will most often distribute UTC (Coordinated Universal Time) along with well planed leap second modifications. But no other information like time zone can be forwarded with it. It means that your devices can get the clocks sync with NTP but you first need to be sure that you configured time-zone on that device so that he can show local time.

With Marzullo algorithm’s help, NTP can refuse to accept the possible consequences of the variable’s latency. But NTP can, over internet, by and large retain time to around tens of the milliseconds. Moreover, in case of LANs (local area networks), there is one millisecond chance of accuracy. NTP 64-bit timestamps, that are consisted seconds part (32 bits) and a fractional second part (32 bits), gives to it (Network Time Protocol) a time scale. The function of this time scale is to roll over at each 2³² seconds etc.

But to perform the clock synchronization function, a remote server and NTP client must calculate the RTD (round trip delay time) as well as offset. The formula to compute RTD is δ = (t₃ − t₀) − (t₂ − t₁), where t₀ (request for packet transmission time), t₁ (request for packet reception time), t₂ (response for packet transmission’s time) and t₃ (response for packet reception’s time) while t₃ − t₀ (time slip away on the client side) etc.

But NTP synchronization is only be exact when both sides’ inward and departing routes between the client side as well as the server side are having symmetrical nominal transmission delay. If there will be no such a general nominal delay for routes existed, the chance of systematic bias of synchronization is possible due to forward and backward travel’s times differences.

The subsequent three NTP architecture’s structures are existed for the use over the internet. These are:

1. Flat peer architecture structure
2. Hierarchical architecture structure
3. Star structure

As to work, NTP can use a hierarchical structure, but it will be a semi-layered system of clock source levels. Each level can be expressed as a stratum. But the initial value of upper most stratum should be 0. Besides this, according to this hierarchical structure, routing pecking order will be derivative from the NTP hierarchy. Such as central part router must have a client/server connection with the outer time sources. Similarly, the inner time server must have a client/server correlation with the center routers and so on. But in the case of star structure, all the involved routers contain a client/server association with few time servers available in the middle. Well! Peer with reference to NTP is referred to the NTP protocol instantiation over a remote processor linked via a network pathway from the neighboring node.

As a curiosity, David L Mills (University of Delaware) had designed this protocol.