frequency of updation - NTP

This is a discussion on frequency of updation - NTP ; Actually I want to know how frequently a system's time get get updated by any NTP server. I didn't found in man pages that it can be done with user interference. So I think this is something done by deamon ...

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Thread: frequency of updation

  1. frequency of updation

    Actually I want to know how frequently a system's time get get updated
    by any NTP server.
    I didn't found in man pages that it can be done with user interference.
    So I think this is something done by deamon itself. And the frequency
    is hardcoded inside its source code.

    If it is so it may happen that it will over load the cpu. Because it
    must be updating itself with some
    transmission and recepton of packets from server.

    So how to know that how frequently a system get itself updated with
    that of a NTP server and is it uniform ?

    Is there any chance of getting a cpu overloaded due to this updation or
    due to any operation of xntpd deamon ?

    thanks in advance.


  2. Re: frequency of updation

    lulu wrote:
    > Actually I want to know how frequently a system's time get get updated
    > by any NTP server.
    > I didn't found in man pages that it can be done with user
    > interference. So I think this is something done by deamon itself. And
    > the frequency is hardcoded inside its source code.
    >
    > If it is so it may happen that it will over load the cpu. Because it
    > must be updating itself with some
    > transmission and recepton of packets from server.
    >
    > So how to know that how frequently a system get itself updated with
    > that of a NTP server and is it uniform ?
    >
    > Is there any chance of getting a cpu overloaded due to this updation
    > or due to any operation of xntpd deamon ?
    >
    > thanks in advance.


    [simple explanation]

    An NTP client (by default) will ask each server for a new time every 64
    seconds when it starts up. As the client time becomes correct, the
    interval between requests will gradually lengthen until it reaches 1024
    seconds. It is not hard-coded, but dynamic and adaptive, and will reduce
    again if needed.

    There is no chance of CPU overload.

    David



  3. Re: frequency of updation

    Is this decision of changing the interval dynamically done by any
    algorithm
    present in rfc related to NTP.

    Can't the user interfere in changing the time interval in which a
    NTP-client sends or recieve packets

    And how of sure u are saying it will never overload the CPU. Because
    sending a packet every minute can make a system overloaded at times
    also if it is side by side working on
    any resource hunting process. So what i mean to askcan't a user control
    th packaet sending and recieving interval manually.


  4. Re: frequency of updation

    lulu wrote:
    > Is this decision of changing the interval dynamically done by any
    > algorithm
    > present in rfc related to NTP.


    I believe the algorithm is documented in Dr Mills papers.

    http://www.eecis.udel.edu/%7emills/ntp.html

    > Can't the user interfere in changing the time interval in which a
    > NTP-client sends or recieve packets


    You can set the minimum and maximum intervals.

    > And how of sure u are saying it will never overload the CPU. Because
    > sending a packet every minute can make a system overloaded at times
    > also if it is side by side working on
    > any resource hunting process. So what i mean to askcan't a user
    > control th packaet sending and recieving interval manually.


    In my own experience I have never seen anything remotely resembling an
    overload on a client system. If a server has thousands of clients, the
    load on the server may need to be considered.

    David



  5. Re: frequency of updation

    lulu wrote:

    > Is this decision of changing the interval dynamically done by any
    > algorithm
    > present in rfc related to NTP.
    >

    Yes. The math is way over my head but it's there

    > Can't the user interfere in changing the time interval in which a
    > NTP-client sends or recieve packets
    >

    Yes, but it's a bad idea if you want good timekeeping. The optimum
    polling interval changes with network behavior and the behavior of your
    local clock.

    > And how of sure u are saying it will never overload the CPU. Because
    > sending a packet every minute can make a system overloaded at times
    > also if it is side by side working on
    > any resource hunting process. So what i mean to askcan't a user control
    > th packaet sending and recieving interval manually.


    Others may be able to offer something like proof but I would guess that
    ntpd would use less than one percent of just about any CPU manufactured
    in the last five to eight years.

    >


  6. Re: frequency of updation

    Thanks a lot for the answers

    I have one more doubt. Let's say I have two cards in one system out of
    which one connected to internet and synching its time appropriately
    with stratum-2 server.
    But I have connected another two system through another card. So right
    now I make
    theses two machine behave the machine having two cards as a NTP server
    for them. ( By changing the ntp.conf as SERVER < INTERNET CONNECTED
    IP> )

    Made some changes to routing table so that these to local machines who
    are connected
    2nd card( not connected to internet) can ping to the ist interface.

    But still these two servers are not sysncing teir time .


  7. Re: frequency of updation

    "lulu" wrote in message
    news:1164801470.404384.20580@j72g2000cwa.googlegro ups.com...
    > Is this decision of changing the interval dynamically done by any
    > algorithm
    > present in rfc related to NTP.
    >
    > Can't the user interfere in changing the time interval in which a
    > NTP-client sends or recieve packets
    >
    > And how of sure u are saying it will never overload the CPU. Because
    > sending a packet every minute can make a system overloaded at times
    > also if it is side by side working on
    > any resource hunting process. So what i mean to askcan't a user control
    > th packaet sending and recieving interval manually.
    >


    lulu, if it's any help, my Stratum 2 pool.ntp.org server is a Linux system
    running on an Athlon XP 2400+ processor. It suffers no noticable load under
    normal conditions, which is about 1500 clients, but even when the server
    shows up in the NTP pool DNS, pushing client levels very high (I've seen it
    as high as 9731 clients), the load was minimal, all according to Wayne
    Schlitt's scripts. Network traffic is really not that much either, ~5 or 6
    KB/sec under very high client levels if I remember correctly.

    Dennis



  8. Re: frequency of updation

    On 2006-11-29, lulu wrote:

    > Let's say I have two cards in one system out of which one connected to
    > internet and synching its time appropriately with stratum-2 server.
    >
    > But I have connected another two system through another card.
    >
    > So right now I make theses two machine behave the machine having two
    > cards as a NTP server for them. ( By changing the ntp.conf


    The ntp.conf on the clients.

    > as SERVER < INTERNET CONNECTED IP> )
    >
    > Made some changes to routing table


    ntpd binds all of the interfaces. So you can point your clients at the
    IP address of the interface they are connected to. Then you won't have
    to complicate your configuration with unnecessary routing.

    > But still these two servers are not sysncing teir time .


    Is your server synced to a source of time (e.g. remote time server or
    local ref-clock)?

    Is port 123/UDP open on both your server and its clients?

    Are there any restrictions which may be blocking ntp packets between
    your server and its clients?

    Have you tried pointing your clients at the server's internal interface?

    --
    Steve Kostecke
    NTP Public Services Project - http://ntp.isc.org/

  9. Re: frequency of updation


    Steve Kostecke wrote:
    > On 2006-11-29, lulu wrote:
    >
    > > Let's say I have two cards in one system out of which one connected to
    > > internet and synching its time appropriately with stratum-2 server.
    > >
    > > But I have connected another two system through another card.
    > >
    > > So right now I make theses two machine behave the machine having two
    > > cards as a NTP server for them. ( By changing the ntp.conf

    >
    > The ntp.conf on the clients.
    >
    > > as SERVER < INTERNET CONNECTED IP> )
    > >
    > > Made some changes to routing table

    >
    > ntpd binds all of the interfaces. So you can point your clients at the
    > IP address of the interface they are connected to. Then you won't have
    > to complicate your configuration with unnecessary routing.
    >
    > > But still these two servers are not sysncing teir time .

    >
    > Is your server synced to a source of time (e.g. remote time server or
    > local ref-clock)?
    >

    Sorry in the line "two server are not synching ..." infact it is the
    two clients are not synching their time. And my server system is
    sysnching to a startum-2 server in the net as said before. That
    interface

    > Is port 123/UDP open on both your server and its clients?
    >

    I couldn't able to get port is open means what ? As I guess u mean to
    ask whether both cleint and server using that port or not , then it is
    yes .
    > Are there any restrictions which may be blocking ntp packets between
    > your server and its clients?

    There is no restriction ..

    > Have you tried pointing your clients at the server's internal interface?
    >

    Inernal interface , i think u mean to say the local interface which is
    not connected to internet for the stratum-2 server .
    > --
    > Steve Kostecke
    > NTP Public Services Project - http://ntp.isc.org/



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