3 Peer server at same stratum - NTP

This is a discussion on 3 Peer server at same stratum - NTP ; If I have 3 time servers (at same stratum) in my lan where each server is indipendent and has set several NTP servers of stratum 1; I 'd like creating redundancy so I think to insert peer option (using symmetric ...

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  1. 3 Peer server at same stratum

    If I have 3 time servers (at same stratum) in my lan where each server
    is indipendent and has set several NTP servers of stratum 1; I 'd like
    creating redundancy so I think to insert peer option (using symmetric
    mode) in ntp.conf for all 3 servers.

    A
    peer B
    peer C

    B
    peer A
    peer C

    C
    peer A
    peer B

    I read documens about ntp but I have always some doubts.

    1 - which NTP server (among these 3) become active ?
    2 - The others two go into passive mode ?
    3 - What logic permit to the NTP server of these 3 to be elected
    active ?


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  2. Re: 3 Peer server at same stratum

    castellani.riccardo@tiscali.it wrote:
    > If I have 3 time servers (at same stratum) in my lan where each server
    > is indipendent and has set several NTP servers of stratum 1; I 'd like
    > creating redundancy so I think to insert peer option (using symmetric
    > mode) in ntp.conf for all 3 servers.
    >
    > A
    > peer B
    > peer C
    >
    > B
    > peer A
    > peer C
    >
    > C
    > peer A
    > peer B
    >
    > I read documens about ntp but I have always some doubts.
    >
    > 1 - which NTP server (among these 3) become active ?


    All three!

    > 2 - The others two go into passive mode ?


    No!

    > 3 - What logic permit to the NTP server of these 3 to be elected
    > active ?


    All three are "active". They share time information among themselves
    and any one of them can serve time to clients.
    >



  3. Re: 3 Peer server at same stratum

    Ok, How is't possible that these three peer servers share time information
    among themselves ?

    For example:
    Server "A" shall retrieve time information (for example "TI-1") from public
    server of stratum 1 (ntp1.ien.it),
    Server "B" shall retrieve time information (for example "TI-2") from public
    server of stratum 1 (ntp2.fau.de),
    Server "C" shall retrieve time information (for example "TI-3") from public
    server of stratum 1 (ptbtime1.ptb.de),

    TI-1, TI-2, TI-3 are three time information which are many similar but they
    can't being the same time(for few milliseconds), so "two of them" must align
    with the other in order to share time information, I think.
    What's logic to select the server (among these 3 peers) which gives reliable
    time to two others ?

    Thanks Richard


    "Richard B. gilbert" ha scritto nel messaggio
    news:45E970D4.4040007@comcast.net...
    castellani.riccardo@tiscali.it wrote:
    > If I have 3 time servers (at same stratum) in my lan where each server
    > is indipendent and has set several NTP servers of stratum 1; I 'd like
    > creating redundancy so I think to insert peer option (using symmetric
    > mode) in ntp.conf for all 3 servers.
    >
    > A
    > peer B
    > peer C
    >
    > B
    > peer A
    > peer C
    >
    > C
    > peer A
    > peer B
    >
    > I read documens about ntp but I have always some doubts.
    >
    > 1 - which NTP server (among these 3) become active ?


    All three!

    > 2 - The others two go into passive mode ?


    No!

    > 3 - What logic permit to the NTP server of these 3 to be elected
    > active ?


    All three are "active". They share time information among themselves
    and any one of them can serve time to clients.
    >




  4. Re: 3 Peer server at same stratum

    Riccardo,

    Riccardo wrote:
    > What's logic to select the server (among these 3 peers) which gives reliable
    > time to two others ?


    In your example, each of the TI-x servers in fact has three sources of
    synchronisation: the external (internet-based) server and the other two
    TI-x servers.

    Each of the TI-x servers applies the NTP algorithms (selection,
    clustering/filtering, combining, discipline) and serves time to clients
    and peers. Note that the time served by each server takes into account
    (i.e. is a combination of) the time stamps received from all of the
    survivors of the filtering algorithm (up to a maximum of 10, in ntpd at
    least).


    Cheers, Jan

  5. Re: 3 Peer server at same stratum

    Riccardo wrote:
    > Ok, How is't possible that these three peer servers share time information
    > among themselves ?
    >
    > For example:
    > Server "A" shall retrieve time information (for example "TI-1") from public
    > server of stratum 1 (ntp1.ien.it),
    > Server "B" shall retrieve time information (for example "TI-2") from public
    > server of stratum 1 (ntp2.fau.de),
    > Server "C" shall retrieve time information (for example "TI-3") from public
    > server of stratum 1 (ptbtime1.ptb.de),
    >
    > TI-1, TI-2, TI-3 are three time information which are many similar but they
    > can't being the same time(for few milliseconds), so "two of them" must align
    > with the other in order to share time information, I think.
    > What's logic to select the server (among these 3 peers) which gives reliable
    > time to two others ?


    Server "A" should get time from servers AS1, AS2, AS3 and AS4. Four
    servers is the minimum for reliability.

    Server "B" should get time from BS1, AS2, AS3, and AS4. (note that one
    server, BS1, is unique.)

    Server "C" should get time from AS1, CS2, AS3, and AS4. Again, one
    server is unique.

    Server "D" should get time from AS1, AS2, DS3, and AS4.

    Without at least one unique server a peer really has nothing to contribute.

    I believe that the peers are then supposed to debate with each other and
    converge to a common time. See Professor Mills' slides (links at
    http://ntp.org/) for the details.


  6. Re: 3 Peer server at same stratum

    On 4 Mar, 16:18, "Richard B. gilbert" wrote:
    > Riccardo wrote:
    > > Ok, How is't possible that these three peer servers share time information
    > > among themselves ?

    >
    > > For example:
    > > Server "A" shall retrieve time information (for example "TI-1") from public
    > > server of stratum 1 (ntp1.ien.it),
    > > Server "B" shall retrieve time information (for example "TI-2") from public
    > > server of stratum 1 (ntp2.fau.de),
    > > Server "C" shall retrieve time information (for example "TI-3") from public
    > > server of stratum 1 (ptbtime1.ptb.de),

    >
    > > TI-1, TI-2, TI-3 are three time information which are many similar but they
    > > can't being the same time(for few milliseconds), so "two of them" must align
    > > with the other in order to share time information, I think.
    > > What's logic to select the server (among these 3 peers) which gives reliable
    > > time to two others ?

    >
    > Server "A" should get time from servers AS1, AS2, AS3 and AS4. Four
    > servers is the minimum for reliability.
    >
    > Server "B" should get time from BS1, AS2, AS3, and AS4. (note that one
    > server, BS1, is unique.)
    >
    > Server "C" should get time from AS1, CS2, AS3, and AS4. Again, one
    > server is unique.
    >
    > Server "D" should get time from AS1, AS2, DS3, and AS4.
    >
    > Without at least one unique server a peer really has nothing to contribute.
    >
    > I believe that the peers are then supposed to debate with each other and
    > converge to a common time. See Professor Mills' slides (links athttp://ntp.org/) for the details.




    I shall configure my NTP peer servers according to your above
    suggestions, but for redundancy do you think that it's necessary to
    change stratum level for each peer server(server A,B,C) of my lan ?
    (for instance server A stratum 10, server B stratum 11, server C
    stratum 12). What do you suggest me ?


  7. Re: 3 Peer server at same stratum

    On 4 Mar, 11:54, Jan Ceuleers wrote:
    > Riccardo,
    >
    > Riccardo wrote:
    > > What's logic to select the server (among these 3 peers) which gives reliable
    > > time to two others ?

    >
    > In your example, each of the TI-x servers in fact has three sources of
    > synchronisation: the external (internet-based) server and the other two
    > TI-x servers.
    >
    > Each of the TI-x servers applies the NTP algorithms (selection,
    > clustering/filtering, combining, discipline) and serves time to clients
    > and peers. Note that the time served by each server takes into account
    > (i.e. is a combination of) the time stamps received from all of the
    > survivors of the filtering algorithm (up to a maximum of 10, in ntpd at
    > least).
    >
    > Cheers, Jan



    > Each of the TI-x servers applies the NTP algorithms (selection,
    > clustering/filtering, combining, discipline) and serves time to clients
    > and peers.


    But does each peer server (in comparison with others two servers)
    serve same or different time to clients ?
    I don't understand if these 3 peer servers synchronize themselves
    among them establishing a share time.

    Note that the time served by each server takes into account
    > (i.e. is a combination of) the time stamps received from all of the
    > survivors of the filtering algorithm (up to a maximum of 10, in ntpd at
    > least).


    For redundancy do you think that it's necessary to change stratum
    level for each peer server (server A,B,C) of my lan ?
    (for instance server A stratum 10, server B stratum 11, server C
    stratum 12). What do you suggest me ?




  8. Re: 3 Peer server at same stratum

    RICCARDO wrote:
    > On 4 Mar, 16:18, "Richard B. gilbert" wrote:
    >
    >>Riccardo wrote:
    >>
    >>>Ok, How is't possible that these three peer servers share time information
    >>>among themselves ?

    >>
    >>>For example:
    >>>Server "A" shall retrieve time information (for example "TI-1") from public
    >>>server of stratum 1 (ntp1.ien.it),
    >>>Server "B" shall retrieve time information (for example "TI-2") from public
    >>>server of stratum 1 (ntp2.fau.de),
    >>>Server "C" shall retrieve time information (for example "TI-3") from public
    >>>server of stratum 1 (ptbtime1.ptb.de),

    >>
    >>>TI-1, TI-2, TI-3 are three time information which are many similar but they
    >>>can't being the same time(for few milliseconds), so "two of them" must align
    >>>with the other in order to share time information, I think.
    >>>What's logic to select the server (among these 3 peers) which gives reliable
    >>>time to two others ?

    >>
    >>Server "A" should get time from servers AS1, AS2, AS3 and AS4. Four
    >>servers is the minimum for reliability.
    >>
    >>Server "B" should get time from BS1, AS2, AS3, and AS4. (note that one
    >>server, BS1, is unique.)
    >>
    >>Server "C" should get time from AS1, CS2, AS3, and AS4. Again, one
    >>server is unique.
    >>
    >>Server "D" should get time from AS1, AS2, DS3, and AS4.
    >>
    >>Without at least one unique server a peer really has nothing to contribute.
    >>
    >>I believe that the peers are then supposed to debate with each other and
    >>converge to a common time. See Professor Mills' slides (links athttp://ntp.org/) for the details.

    >
    >
    >
    >
    > I shall configure my NTP peer servers according to your above
    > suggestions, but for redundancy do you think that it's necessary to
    > change stratum level for each peer server(server A,B,C) of my lan ?
    > (for instance server A stratum 10, server B stratum 11, server C
    > stratum 12). What do you suggest me ?
    >


    It is not necessary to change the stratum of any of the peers. Each one
    will set its own stratum depending on the stratum of the synchronization
    source. A machine synchronized to a stratum two internet server will
    become stratum 3.

    Configure your clients to use all of your peered server. If any server
    fails, the clients will continue to use the other three without problems.





  9. Re: 3 Peer server at same stratum

    >>> In article <1173085062.161146.301350@p10g2000cwp.googlegroups. com>, "RICCARDO" writes:

    RICCARDO> I shall configure my NTP peer servers according to your above
    RICCARDO> suggestions, but for redundancy do you think that it's necessary
    RICCARDO> to change stratum level for each peer server(server A,B,C) of my
    RICCARDO> lan ? (for instance server A stratum 10, server B stratum 11,
    RICCARDO> server C stratum 12). What do you suggest me ?

    I recommend you see:

    http://ntp.isc.org/Support/ConfiguringOrphanMode

    for the new way of handling this, and if you want to see the old way:

    http://ntp.isc.org/Support/ConfiguringLocalRefclocks

    H

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