[ntp:questions] Re: Philosophical question about strata
Richard B. Gilbert
rgilbert88 at comcast.net
Fri Oct 7 17:03:42 UTC 2005
Lee Sailer wrote:
>I had this thought about strata and I am hoping someone might have some
>ideas to contribute.
>Suppose you have two ntp clients that get their time from multiple
>strata 1 servers. They should be very accurate statum 2 servers as a
Should! Probably will be.
>Now later, you are configuring a new client, and for some reason you
>have a choice. You can use one of the stratum 1 servers, or the
>stratum 2 server. (I know, make another choice. This is a theoretical
>It seems to me that the right choice is the stratum 2 server. Am I
You are not wrong! Most public stratum 1 servers are stretched to
nearly the breaking point! EVERYBODY wants to use a stratum 1
server. Now if you are talking about using a private stratum 1 server
under your ownership and control, or if you would be using it with the
explicit and voluntary consent of the owner, then feel free.
>However, if you configure this new client so that it uses one stratum 1
>the stratum 2, I think the algorithm will choose the stratum 1. Again,
>am I wrong?
Again you are not wrong. Lower stratum wins every time. (Well almost....)
>Basically, my thought is that it is possible for a stratum 2 source to
>be better than a stratum 1 source, and likewise for a stratum n source
>to be better than a stratum m source, where n > m.
You are right. Stratum 2 servers tend to be less heavily loaded, tend
to respond more quickly, and tend to have a lower round trip delay if
you pick servers close to you. There are a lot more stratum 2 servers
to choose from. Some of them can actually be better than a stratum 1
server; a server using an HF receiver to synch to WWV or a VLF receiver
to synchronize to WWVB is technically stratum 1 but the vagaries of
radio propagation can cause them to have poorer quality time than a
stratum 2 server synchronized to a stratum 1 server using GPS. I
operate two stratum 1 servers in my home; one GPS and one WWV. The GPS
server works very well and compares well with the best public stratum 1
servers. The WWV synched server can be within a millisecond or two if
radio propagation conditions are favorable or off by twenty to forty
milliseconds when conditions are not favorable.
>Comments welcome. No flames please.
>Flamed online since 1977
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