Con ntpdate !

ntpdate è già presente di default su molte distro, Ubuntu compreso. Vediamo la procedura:

da shell digitiamo:

sudo nano -w /etc/cron.daily/ntpdate

e inseriamo questa riga:

ntpdate ntp.ubuntu.com

Dopodichè diamo i permessi di esecuzione:

sudo chmod +x /etc/cron.daily/ntpdate

Oppure:

sudo chmod 755 /etc/cron.daily/ntpdate

L'orario verrà sincronizzato e aggiornato di giorno in giorno.

What in fact they are referring to is that they have an NTP server that receives a timing source from an atomic clock. However, just because atomic clocks are the most accurate chronometers in the world, accurate to a few nanoseconds (billionth of a second) it doesn’t necessarily mean that a network using one as a timing source is receiving the same sort of accuracy

Atomic clocks work on the principle that certain atoms (in most atomic clocks the caesium -133 atom) oscillates at an exact frequency at certain energy levels. In the case of the caesium atom it resonates at exactly 9,192,631,770 every second.  Because of this exact resonance, atomic clocks lose less than a second in millions of years. In fact, the resonance of the caesium atom is so precise that the International System of Units has defined the second as exactly that number of oscillations of the caesium atom.

NTP servers can receive the time from an atomic clock through several sources. Obviously the Internet contains thousands of timing servers, some of which are hooked up to an atomic clock, others however, can be over ten seconds out of sync.

Furthermore, using an Internet timing source can leave a system open to abuse as the timing references cannot be authenticated. Also, the distance from a host, client and server can make dramatic differences in the accuracy.

The most accurate and effective way of receiving a timing source from an atomic clock is to use the national time and frequency broadcast that several country’s national physics laboratories transmit. Alternatively the American GPS (Global Positioning System) transmits the time from its own satellite’s atomic clocks. both methods can provide perfect synchronisation and accuracy to within a few milliseconds.

NTP is installed on most versions of Windows (although a stripped down version called SNTP is in older versions) and Linux but regardless is open source an free to download from ntp.org.

To synchronise a network it is preferable to use a dedicated NTP server that receives a timing source from an atomic clock either from specialist national radio transmissions or the US GPS system, although Internet time references are available but some are more reliable than others (and none can be authenticated leaving a system open to attack).

NTP is hierarchical, it is arranged into stratum. Stratum 0 is a timing source (such as an atomic clock) while stratum 1 is a server connected to a stratum 0 server and a stratum 2 is a computer (or device) attached to a stratum 1 server.

There is an understanding that if using a public Internet based time server, stratum 0 servers are not used by most applications as too many requests would disable them. Instead NTP should be configured to receive a timing reference from several stratum 1 and stratum 2 servers (it is good housekeeping to use more than one as it is possible one server could go down).

The most accurate and secure way of synchronising a network is to use a dedicated NTP server. These can receive a timing reference from either the GPS network (as each GPS satellite contains an atomic clock and broadcasts the signal) or a specialist national radio transmission. Both of these signals come from a stratum 0 source and both provide accuracy to within a few milliseconds.

NTP was developed and designed in 1985 by Professor David Mills from the University of Delaware in the United States. Its success owes much to the fact that it was one of the first ever protocols on the Internet and was first used when the World Wide Web was in its infancy.

The importance of NTP on modern computer networks cannot be stressed highly enough, without NTP and NTP servers many of the applications and processes that we conduct over the Internet and now take for granted

Internet auction sites, email and global trading all require accurate time synchronisation. Just imagine booking an airline ticket only to discover your seat was resold after you had purchased it because the buyer had a slower clock on their computer?

Confusion and problems such as these would be commonplace without NTP and NTP servers, just think of the hysteria around the millennium bug!

NTP servers allow not only computers on a particular network to be perfectly synchronised but as most NTP servers are set to receive time from a UTC time source, computers around the entire globe can be synchronised together. UTC or Coordinated Universal Time is a global time scale based on the time told by atomic clocks.

NTP servers can receive a timing reference from the Internet, although this is fairly inaccurate, or from dedicated time and frequency radio signals or the GPS network.

Currently an NTP server receiving an authoritative timing source can provide accuracy over the Internet to within a few hundred nanoseconds (a nanosecond is 1 second every billion years.)

Time, in the form of timestamps, provides the only frame of reference between all devices on a network and the way an NTP server works is pretty straightforward. The timestamp relayed to the server is in the form of an ever increasing number that started from a set point in time, this is known as the prime epoch and for most systems this started on 1 January, 1900.

The NTP server checks the time stamp from an authoritative source, normally a UTC source (Coordinated Universal Time, a global timescale based on the time told by atomic clocks), from either the Internet, a radio transmission or via the GPS network.

The NTP server uses the timestamp to calculate if the network clocks are drifting and adds or subtracts a second to match the reference clock. The NTP server will do this at set intervals, normally every fifteen minutes to ensure perfect accuracy.

NTP is accurate to within 1/100th of a second (10 milliseconds) over the public Internet and can perform even better over LANs and WANS with accuracies of 1/5000th of a second (200 microseconds) not unheard of.

To ensure further accuracy the NTP service (or daemon on Linux) which runs in the background and does not believe the time it is told until after several exchanges and each one has passed a protocol specification (a test), the server is then considered. It usually takes about five good samples) until a NTP server is accepted as a timing source.

NTP (Network Time Protocol) is an Internet protocol designed for the synchronisation of computer networks. NTP servers are used by millions of system administrators to ensure their networks are keeping accurate time.

However, just as a computer is only as a good as the software it is running, a NTP server is only as good as the timing source it receives.

Despite the hundreds and probably thousands of possible timing references on the Internet, administrators should be aware of some of the possible pitfalls in selecting a timing reference.

A survey conducted by the Massachusetts Institute of Technology (MIT) discovered that not only were half of Internet timing sources inaccurate by over a ten seconds (a lifetime if we are attempting millisecond accuracy) but many were too far away to be provide any useful accuracy.

If an Internet timing source is to be used then not only should the accuracy of the server be checked but also the closest host should be selected to ensure the best accuracy.

Another consideration in using an Internet timing source is to be aware that they cannot be authenticated which means that your system could be vulnerable to malicious attacks and it is recommended by Microsoft and Novell that an external hardware source should be used.

The most secure and accurate method of receiving a timing source is to use a dedicated NTP server that can receive either a national time and frequency transmission (such as WWVB in the US or MSF in the UK). Alternatively a timing source can be received from the GPS network (Global Positioning System), both methods are authenticated and can provide millisecond accuracy.

These are the steps required.

1. run: sudo aptitude install ntpd
2. run: vi /etc/ntp.conf (assuming you have vim tools installed)
3. locate "server" and added the address of the NTP server instead of 127.0.0.1
4. run: cp /usr/share/zoneinfo/Europe/Malta /etc/localtime (amend this according to your timezone)
5. run: /etc/init.d/ntp restart (to restart the service)
6. Next we have to check if the NTP server was picked up and the status of the synchronization, run: ntpq
7. run: peers (see first screenshot)
8. Check that the Peer Remote has been populated with the NTP server address inserted in the ntp.conf previously , ref id: is the high order stratum NTP server. What is most important here is the reach, since this increments accornding to how reliable the NTP (local) server is, and the poll, which will increase polling time if servers is reliable.
9. run: association, and check the status. If you just restarted the NTP service, and the polling and reach values are low, than the condition would be rejected.
10. After some time, when the reach values increase (meaning server is reliable and therefore also the poll interval increases) running once again the command association will return a different output. (see second screenshot). The condition will change to sys.peer
    
11. Running peers once again will now output  reach 377 which means the data connection is good and an * which means preferred server. The Poll interval will also increase from 64 any larger number over time.

Further details can be found here: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1339

watch "ntpq -p"

Press Ctrl-c to stop watching the process.

Note the information in the following columns:

• The character in the first column indicates the quality of the source.
• The asterisk ( * ) indicates the source is the current reference.
• remote lists the IP address or host name of the source.
• when indicates how many seconds have passed since the source was polled.
• poll indicates the polling interval. This value increases depending on the accuracy of the local clock.
• reach is an octal number that indicates reachability of the source. A value of 377 indicates the source has answered the last eight consecutive polls.
• offset is the time difference between the source and the local clock in milliseconds"

Включить запуск сервиса:
# chkconfig ntpd on

Синхронизировать время с with 0.pool.ntp.org:
# ntpdate pool.ntp.org

Запустить NTP:
# /etc/init.d/ntpd start

The ‘CCIE Quickfire’ workbook I have created is maturing nicely; I have been running through all of the questions at least twice a day over the last few days and it’s becoming a fantastic tool to aid my short and long term memory of all things routing and switching.  I have been using the 2 hours of study in the evening to review notes and then update the workbook with new questions for each technology I come up against, I am however going to need to re-arrange the workbook every now and again - knowing ‘Ethernet Basics’ inside-out obviously isn’t as important as knowing ‘BGP’ yet I’ll be answering the questions on it many more times the way the workbook is arranged at the moment…..
Here is a copy of the workbook as it is at now (right click – save target as), my colleague “SP” has been a great help to me over the last few days because he has also worked through a few questions and pointed out little bits of information I should add in.

I’ve spotted one or two excellent articles around the ‘blogosphere’ during the last week, here are some of them:
1) “U.U.U.U” à ever wondered what this means? à head-over to packetlife.net to find out
2) Tutorial: Filtering Routes in OSPF Part 1 » Filtering Within An Area by Arden Packeer
3)  CCIE Job Searching by Emmanuel Conde
4) A series of MPLS related articles by Human Modem

An announcement:
I will be moving onwards and upwards next month into a Systems Engineer role at Cisco! J  I am over-the-moon, it was a dream of mine when I focused on networking just 4 years ago that I didn’t think would ever materialize – and now it has!  I really can’t wait for the opportunity to work within such a dynamic and prestigious company. J
One of my first tasks within my new role will be a trip to San Jose – I have earmarked the evenings in the hotel as ‘intense-study’ evenings, hopefully that time will take me past the 350-001 ‘knowledge-line’ and get a base-level in place ready for lab prep.
I think you will now understand why my manager has asked me to postpone my 350-001 written exam for a few weeks.

Here is an example for a Rail Mount NTP Server

Usually the time server is mounted into the Rack with two screws on each site's holder clamp.

You can see my minor Photoshop skills here:

The above photo is Meinnberg's PTP and NTP capable Rackmount NTP Server with GPS synchronization.

date 060612212008.10
установит дату 6 месяц (июнь) 6ое число 12 часов 21 минуту 2008ой год 10 секунд

Для настройки синхронизации времени в Арче, понадобиться openntpd
#yaourt -S openttpd
Открываем файл настройки ntp сервера
nano /etc/ntpd.conf

прописываем там, сервера синхронизации времени
server 0.ru.pool.ntp.org
server 1.ru.pool.ntp.org
server 2.ru.pool.ntp.org
server 3.ru.pool.ntp.org
что бы сделать ПК с Арчем сервером синхронизации времени нужно добавить по вкусу строчку
listen on xxx.xxx.xxx.xxx #вместо xxx ваш ip

запускаем ntpd
читаем логи
cat /var/log/daemon.log | tail
должно быть что-то вроде этого:
Jun 6 12:59:27 linux ntpd[9943]: ntp engine ready
Jun 6 08:59:51 linux ntpd[9943]: peer 87.236.24.179 now valid

Добавим ntpd что бы служба запускалась при каждой загрузки Арча
nano /etc/rc.conf
DAEMONS=(... ntpd ...)

p.s.: спасибо ссылка1 ссылка2 и отдельную благодарность выражаю man date

So, instead of resetting the internal clock, I wanted to point to an external time source. (tock.usno.navy.mil) I found a great article that takes you through the process step by step.

"If you want to ensure that the clocks on your machines are more accurate in terms of absolute (and not just relative) time, you can sync the PDC Emulator in your forest root domain to one of the reliable time servers available on the Internet. This is a good idea if your company is a large enterprise with sites spanning several countries, or if your organization has two or more forests linked by forest trusts. The procedure for doing this on a PDC Emulator running Windows Server 2003 in the forest root domain is as follows. Open Registry Editor (regedit.exe) and configure the following registry entries:

HKLM\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\Type

This registry entry determines which peers W32Time will accept synchronization from. Change this REG_SZ value from NT5DS to NTP so the PDC Emulator synchronizes from the list of reliable time servers specified in the NtpServer registry entry described below.

HKLM\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags

This registry entry controls whether the local computer is marked as a reliable time server (which is only possible if the previous registry entry is set to NTP as described above). Change this REG_DWORD value from 10 to 5 here.

HKLM\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\NtpServer

This registry entry specifies a space-delimited list of stratum 1 time servers from which the local computer can obtain reliable time stamps. The list may consist of one or more DNS names or IP addresses (if DNS names are used then you must append ,0x1 to the end of each DNS name). For example, to synchronize the PDC Emulator in your forest root domain with tock.usno.navy.mil, an open-access SNTP time server run by the United States Naval Observatory, change the value of the NtpServer registry entry from time.windows.com,0x1 to tock.usno.navy.mil,0x1 here. Alternatively, you can specify the IP address of this time server, which is 192.5.41.209 instead.

Now stop and restart the Windows Time service using the following commands:

net stop w32time

net start w32time

It may take an hour or so for the PDC Emulator to fully synchronize with the external time server because of the nature of the polling method W32Time uses. Depending on the latency of your Internet connection, the accuracy of the CMOS clock on your forest root PDC Emulator may be within a second or two of UTC. If you need more accurate time however, you can purchase a hardware time source like an atomic clock and connect it to your PDC emulator.

Alternatively, if you don’t want to wait for time convergence to occur between your stratum 2 time server (your forest root PDC Emulator) and the external stratum 1 time server, you can run the following command on your PDC Emulator:

w32tm /resync /rediscover"

Al lanzar un ntptrace, obtenía algo así:

# ntptrace
localhost: stratum 16, offset 0.000000, synch distance 0.012450


cosa, que no tenía sentido, ya que después de localhost debería de aparecer el trace de los servidores a los que este consulta a su vez.

Estos servidores que me daban problemas eran instancias virtuales de Xen, así que al final se me ha ocurrido la feliz idea de mirar en que estado estaba ntp en el host físico. Como se puede imaginar, ntp no estaba instalado. Lo he instalado, he reiniciado los ntp de las instancias virtuales y TACHAN! la hora se ha sincronizado.

La razón de esto se puede encontrar aquí es la siguiente:

The following services are not needed anymore:
* ntpd
the xenU uses the dom0 time
If you want to run ntp in the domU, try: echo 1 > /proc/sys/xen/independent_wallclock

ATAU

# cd /usr/ports/net/ntp
# make; make install
 
Ambil dan pilih salah satu NTP Servers yg diinginkan

kunjungi public ntp list timeserver  ntuk dipilih sebagai NTP server kalian.

 
Buka Port 123 UDP pada firewall

Jika FreeBSD anda menjalankan ipfilter, kamu harus buka port 123 UDP. 

daripada repot copy & paste berikut ini :

pass out quick on lnc0 proto udp from SERVER-KAMU to any port = 123 keep state
ATAU

 pass out quick on lnc0 proto udp from SERVER-KAMU to TIME-SERVER-IP port = 123 keep state  

contohnya, IP FreeBSD workstation adalah 192.168.1.16 dan 61.246.176.131 adalah IP NTP server lalu rule pada ipf.conf file sebagai berikut:

 
pass out quick on lnc0 proto udp from 192.168.1.16 to 61.246.176.131 port = 123 keep state
 

FreeBSD test clock synchronization

jalankan perintah ntpdate :
Set ke tanggal yg salah dahulu (Mon Dec 13 4:27 pm):

# date 0412131627

Sekarang set ke tanggal yang benar dengan ntp client:

# ntpdate -v -b in.pool.ntp.org

Anda dapat memverifikasi kebenaran tanggal tsb:

# date

Output:

Wed Jan 25 12:36:21 IST 2006
 

Jalankan date & time/ clock Synchronization pada saat waktu boot

tambahkan pada file /etc/rc.local .

# vi /etc/rc.local

ntpdate_enable="YES"
ntpdate_hosts="asia.pool.ntp.org"

1. Abrir un terminal, mejor el de root (Aplicaciones>Accesorios>Terminal)

2. Escribís en él: apt-get install ntp (también vale aptitude install ntp y también vale sudo aptitude install ntp o sudo apt-get install ntp desde un terminal normal)

Ahora ya podéis seleccionar la opción de Sincronizar con los servidores de Internet en Ajustar fecha y hora al darle botón derecho al relojito del panel.

Nótese que estos comandos son para Debian y distribuciones que implementen el sistema de Debian de instalación de paquetes. En otro caso deberéis usar emerge o pacman o el que corresponda a vuestra distro en lugar del apt-get o el aptitude.

También podéis abrir el instalador favorito de vuestra distribución (por ejemplo synaptic), buscáis ntp y aplicáis para instalar.

Y pista.

Actualización: en Debian Lenny no sé por qué ha desaparecido el paquetito de marras (ntp) pero en su lugar podemos instalar 'chrony' (apt-get install chrony) que parece que hace el mismo servicio. ]]> http://susmit.wordpress.com/?p=10 Sun, 04 May 2008 04:07:28 +0000 susmit http://susmit.wordpress.com/?p=10 What gives you a euphoric feeling?

For me, it's a sleepless night, a graph (synchronized every half an hour) slowly moving towards the cut in line, combined with, well, a book of cryptography and coding ;).

Yesterday, I (or we at WBUT) configured and included ourselves in the NTP cluster. The machine which hosts this server is orca.wbut.ac.in. From now onwards, most of the time sync requests from India is going to be redirected towards us and we are happy to have them.

As always, we are the first and sole participant from India in the cluster. I am extremely hopeful that we will soon get a few more servers across India.

Anyway, we are currently operating as stratum 2 server. But soon we may be getting hold of a card like this and upgrade ourself to a stratum 1 server.

Before closing, two screenshots.

1. Our score (cut off is 5)

2. And our sync

PS: As this cluster is extremely sensitive, it takes 4-5 hours to re sync once a server is out of sync or rebooted.

- Advanced Router Technology (Part 4): Network Address Translation (NAT)

مدته 33 دقيقة.

يشرح بالتفصيل عن هذا البروتوكول، وبعض المصطلحات المهمة الخاصة به :

• Inside Local Address
• Inside Global Address
• Outside Local Address
• Outside Global Address

ثم ينتقل إلى كيفية تعريفه على الراوتر سواء أردنا تعريفه Static, Dynamic أو Overloaded.

 
- Advanced Router Technology (Part 5): HSRP and NTP

مدته 47 دقيقة

من بين جميع البروتوكولات التي يعج بها الفصل الخامس من الكتاب، يشرح هذا الفيديو بروتوكولي HSRP و NTP. وبنفس الطريقة التفصيلية المعهودة لينتقل بعدها إلى شرح تعريفهما على الراوتر. كان الشرح وافياً وسهلاً ساعدني في ترتيب أفكاري، خصوصاً حول NTP.

This blog will try to give an overview about time synchronization in computer networks via NTP or PTP.

درس حافل بالبروتوكولات... بعضها لدي معرفة بها والآخر لا. أو أني أعرفه ولكن تطبيقه على أجهزة سيسكو هو الجديد بالنسبة لي. لذلك توجهت كثيراً أثناء دراستي لموقع جوجل للبحث عن موضوعات تزيد في استيعابي لما يقوله الكتاب. ولهذا السبب استغرق مني هذا الدرس جلستين.

ملخص الفصل

• بروتوكولات ARP (Address Resolution Protocol), Proxy ARP التي تمكن أجهزة الكمبيوتر من اكتشاف العناوين الفيزيائية  MAC للأجهزة الأخرى الموجودة على الشبكة.
• بروتوكولات RARP (Reverse ARP), BOOTP التي تستطيع الأجهزة من خلالها الحصول على عنوان IP. يقع على عاتق مدير الشبكة عبء تعريف قائمة بها عناوين MAC في الشبكة مع عناوين IP المقابلة لها بشكل يدوي.
• شرح DHCP وهو البروتوكول الدارج حالياً بهدف توزيع عناوين IP على الأجهزة بشكل ديناميكي.  بالإضافة إلى شرح كيفية تعريف جهاز الراوتر كسيرفر DHCP.
• بروتوكولات HSRP, VRRP, GLBP الخاصة بموضوع Gateway

من المعروف أن تعريف TCP/IP على أجهزة الكمبيوتر يتضمن تعريف Gateway وهو جهاز الراوتر الذي سيكون البوابة باتجاه الشبكات الأخرى سواءاً كانت شبكات داخلية أخرى أو شبكة الإنترنت.  إذا تعطل هذا الراوتر فنحن في مشكلة.

تقوم الفكرة من هذه البروتوكولات -كل على طريقته- على اسناد عنواني IP و  MAC إفتراضيين لمجموعة من أجهزة الراوتر. ويستخدم عنوان IP هذا عند تعريف Gateway على الأجهزة بدلاً من العنوان الفعلي. إذا حدث وتعطل أحد الراوترات في المجموعة ينتقل الحمل إلى راوتر آخر ليصبح هو البوابة. وطبعاً هذا يتم دون أن يؤثر على سير العمل ودون الحاجة لتغيير إعدادات Gateway على أجهزة المستخدمين.

• بروتوكول NTP (Network Time Protocol): المسؤؤول عن تصحيح الوقت وتزامنه بين جميع الأجهزة. ويتضمن شرحاً لكيفية تعريف أحد الراوترات أو السويتشات كسيرفر NTP بحيث يكون مرجعاً لباقي الأجهزة لتصحيح ساعاتها.
• بروتوكول SNMP (Simple Network Management Protocol): الخاص بمراقبة أجهزة الشبكة. هناك مقارنة بين إصداراته الأربعة وأنواع الرسائل والمعلومات التي يتبادلها البرنامج المستخدم للمراقبة SNMP Manager والجهاز المراقب.
• Syslog: لتسجيل الأحداث التي تطرأ على الجهاز خلال عمله، بحيث يمكن لمدير الشبكة مراجعتها مثلا عند حدوث مشاكل لمعرفة أسبابها، أو الأحداث التي سبقت أو حدثت لحظة وقوع المشكلة. وهذا قد يتم بالإستعانة  بالبروتوكول السايق واستخدام SNMP Manager.
• WCCP (Web Cache Communication Protocol): شديد الشبة بـِ  Proxy Server حيث يقوم الراوتر بتحويل طلبات HTTP المرسلة من المستخدمين إلى جهاز آخر يدعى Cache Engine أو Content Engine لعله يحوي البيانات المطلوبة، وإلا فإن الطلب يتم  تحويله إلى السيرفر الأصلي. وهذا يتم بشكل خفي على المستخدم (وهنا الفرق بين Proxy Server و WCCP). لأن إعدادات Proxy Server ينبغى تعريفها على أجهزة المستخدمين بينما WCCP يتم تعريفه على الراوتر ولا يعرف المستخدم إذا كانت الصفحة التي طلبها قد أتته من مصدرها الرئيسي أو من أحد أجهزة Cache Engines. شرح ممتاز لهذا البروتوكول على الصفحة التالية في موقع سيسكو  Web Cache Control Protocol Feature Module

This being said, windows time service uses a hierarchical relationship that controls authority and does not permit loops.

The PDC operations master at the root of the forest becomes authoritative for the organization. Microsoft recommends that you configure your authoritative time server to sync with a hardware source, since syncing with external internet sources, does not perform any form of authentication when gathering time information.
To configure the PDC master without using an external time source, change the announce flag on the PDC master. The PDC master is the server that holds the forest root PDC master role for the domain. This configuration forces the PDC master to announce itself as a reliable time

To set it as NTP server, do the following modification in the registry, please backup the registry prior to doing this.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags
In the right pane, right-click AnnounceFlags, and then click Modify.
In Edit DWORD Value, type A in the Value data box, and then click OK.

And then restart w32tm service.

If your application log for the PDC generate the following error, you will need to disable NTP client

Event Type: Warning
Event Source: W32Time
Event Category: None
Event ID: 12
Date: 4/4/2008
Time: 8:38:13 AM
User: N/A
Computer: XXXXX

Description:
Time Provider NtpClient: This machine is configured to use the domain hierarchy to determine its time source, but it is the PDC emulator for the domain at the root of the forest, so there is no machine above it in the domain hierarchy to use as a time source. It is recommended that you either configure a reliable time service in the root domain, or manually configure the PDC to synchronize with an external time source. Otherwise, this machine will function as the authoritative time source in the domain hierarchy. If an external time source is not configured or used for this computer, you may choose to disable the NtpClient.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
To disable NTP client,

Open your registry
Go to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\W32time\TimeProviders\NtpClient
Create or Modify a new dword called "Enable"
Set value as 0 to disable this tweak and 1 to enable this tweak

and reboot the system for it to take effect.

 #1 - From Wikipedia's entry on NTP  (Network Time Protocol)

Background - NTP will soon represent timestamps using two 64bit numbers; one for the whole number of seconds, and one for the fractional part of the second:

According to Mills, "The 64 bit value for the fraction is enough to resolve the amount of time it takes a photon to pass an electron at the speed of light. The 64 bit second value is enough to provide unambiguous time representation until the universe goes dim."^[4] Indeed, 2⁻⁶⁴ seconds is about 54 zeptoseconds, and 2⁶⁴ seconds is about 585 billion years.

That ought to do it.