Public NTP (Network Time Protocol) Service

• Introduction
• NTP Access Request Form
• Frequently-asked Questions with Answers (FAQs)
• Infrequently-asked Questions with Answers (Experts Only)
• References

Introduction

You are welcome to contact our NTP server to update your computer clock. To use the public NTP service, send me a message on the form below to let us know you're using our NTP server. Be sure to include your IP address or address range. Please see the first question below for conditions.

Ideally, please reference our NTP time server by name, ntp.drydog.com. If you must use an IP address (not recommended), the IPv4 and IPv6 addresses (which point to the same host) are currently:

• 74.208.247.59 (IPv4)
• 2001:470:7c:5e7::1 (IPv6)
  Subject to change without notice!

You can also contact us by using on the form below.

Drydog NTP Timekeeper
Drydog Press Network Operations

NTP Access Request Form

Important Notice: In compliance with the Children's Online Privacy Protection Act of 1998, we do not accept requests from children under 13 years of age.

Frequently-asked Questions with Answers (FAQ)

And without further ado, here are the most frequently-asked questions (FAQ).

Q: Can I use your NTP server?
A: Yes. This server is for use by the public. Feel free to use it, subject to these conditions:

• Let me know the IP address or address range that will use this service.
• If you contact this server periodically, please limit requests to once each hour or less. It's best to let your NTP client decide how often to contact the server, if it has that ability.
• If you have a network of machines that you need to synchronize (3 or more), you must run a local NTP time server (that syncs to me) and then have your local clients sync to that local server.
• This service is limited to NTP servers located in the Western United States and Northern Mexico. If you are located elsewhere, please send me a separate request.
• I make no guarantee of accuracy or continued availability of this service.

Q: How do I set up my NTP client software?
That depends on what software you are using. Please consult the documentation that came with your software. See above for the hostname of our NTP service.

Q: Where is software and documentation available?
A: NTP software, including pointers to commercial and non-commercial NTP software, is at http://www.ntp.org/

Q: I get a "connection refused" message when trying to connect to your server. What's wrong?
A: You're probably trying to connect to the wrong TCP/IP port. The NTP server uses UDP port 123 ("ntp"). Other time clients use other time protocols. That is, port 13 ("daytime"), 37 ("time"), or 525 ("timed"). None of these other protocols are supported by this server. Please make sure your client software supports "NTP" and not some other time protocol.

Q: I get a "no route to host" message when trying to connect to your server. What's wrong?
A: The most likely possiblity is your ISP's or your personal's "firewall" is blocking access to NTP's port, 123. Another possiblity is this server is down due to some hardware problem.

Q: How many users do you have?
A: Most days, I see traffic from approximately 500 distinct hosts.

Q: How available is this server?
A: The intention is to provide uninterrupted 7/24 service. However, as a practical manner, this server is available externally about 99% of the time. Most interruptions are due to network connectivity, followed by software issues, power failures, and hardware (usually disk) failures. I will try to keep you informed about network and service status. However, I reserve the right to discontinue this service at anytime without notice.

Q: What is the source of the time at ntp.drydog.com?
A: The machine syncs to three stratum 1 clocks, geographically distributed, operated by NIST.

Q: What timezone does your NTP server use?
A: None. NTP servers use "UTC" time (formerly "GMT" time), which is the same throughout the world. The timezone you are in doesn't matter to this NTP server. The translation to a time zone is handled completely by your NTP client software.

Q: What other network services do you provide?
A: Currently, the machine also serves web (http) and ftp. These are publically-accessible services, but I do not provide public hosting services.

Q: Why do you run this service?
A: Because I can. It takes very little time or computing resources and it is useful to many. This spirit of cooperative anarchy is one of the things that built the Internet that we know today, yet sadly, very few are still practicing it.

Q: Who are you?
A: I'm Dan Anderson. On the Internet, I'm most likely best known for writing the Solaris x86 FAQ and the Simple Whois Daemon. I've been running Internet servers continually since 1994 and I've been actively using the Internet since 1982.

I hope that you find this service useful. If you have any further questions or concerns, or you've just got something to say, feel free to contact me.

—Dan
Timekeeper, drydog.com domain

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Experts Only: Infrequently-asked Questions with Answers

NTP (Network Time Protocol) was invented to synchronize computer clocks in an internet network environment. Unlike other time protocols (e.g., timed), NTP seeks to synch to the most accurate clock rather than "average in" errors from multiple time sources. Clock sources are categorized by stratums (levels) away from master clock sources (that have short-wave radio or GPS connections to the U. S. Naval Observatory).

If a master clock source isn't available, you can arbitrarily choose a system's local clock source (quartz crystal) and use it as your master time server. A crystal in a computer usually isn't an accurate or uniform time source, because of variations in temperature and because the crystals used are usually lower quality as those found your watch. This applies equally to cheap PCs or expensive Sun servers. Only DEC (now Compaq, later HP :-) Alpha servers actually try to use accurate crystals and even those still benefit from NTP. However, at least you can make it a uniform time reference across multiple systems.

NTP is useful for synchronizing the time for software distributed on multiple hosts (for example, RPC, Remote Procedure Calls). Most access control mechanisms use time stamps, and therefore require systems to have their time synchronized. Finally, another benefit of NTP is ensuring accurate timestamps in log files, which greatly aids diagnosting network and network software problems.

• How do I get access to a "real" external clock?
  If you have access to the Internet, see the list of Public NTP Time Servers.

  I run a public time server at ntp.drydog.com (on my own time and own hardware--it's not related to my work or supported by Sun). If you live in Western North America, you're welcome to use it. Please send me a message on the form above to let me know you're using our NTP server.

  To avoid overloading external NTP servers, please don't connect more than two of your NTP servers to an external NTP servers from your site. If you need more, setup your own time server(s).

  You can also use a GPS or a radio clock connected to a Solaris system to serve as a "master time source." You need a driver to access the clock source (be it a radio clock (accessing short-wave station WWV), a GPS, or radio clock). The clock source is usually connected to Solaris through a serial port. Some drivers come with ntpd itself (newer versions have more drivers). Other drivers may be provided by the manufacturer. More background information on NTP is at http://www.ntp.org/

• How do I set the time manually from a NTP time server on the network?
  Run ntpdate(1M) as root. This sets the time immediately from one or more NTP servers specified on the command line (if they are found "suitable"). For example:

  # ntpdate myntpserver 28 Aug 13:57:01 ntpdate[26107]: step time server 192.168.96.107 offset -2.881116 sec

  A message appears only if the current time is off by more than 0.5 seconds. In any case, the time is adjusted. You can't run ntpdate if the ntpd server is running.

• I get this message when ntpd starts: ntpdate: no server suitable for synchronization found
  That's not necessarily an error. Many times ntpdate doesn't trust the time server(s) it's talking to and ignores it (or them). ntpdate is really not needed--it sets the time immediately before the ntpd server starts. ntpd will gradually adjusts the time over a few minutes or several hours depending on how out of sync the local time is. To really see if ntpd is working, wait about 20 minutes after starting ntpd and type the following: ntpq -c peers

  If you keep getting the message and want to get rid of it, try adding another NTP server to your ntp.conf file.

• I get this error message, and ntpd fails to start: no multicast server suitable for synchronization found
  It means there's no multicast NTP server (which uses 224.0.1.1) on your local subnet. You probably just copied the sample /etc/inet/ntp.client file to /etc/inet/ntp.conf To fix this, just comment the "multicastclient 224.0.1.1" line and add "server" lines, 1 for each of your your NTP servers. If you really want to use NTP multicastclients, read the documentation and set up a NTP broadcast server properly.

  If you have a multicast network setup on your local subnet, you can use snoop (as root) to verify there are NTP broadcasts. For example:

  # netstat -rn | egrep 'Gateway|224' Destination Gateway Flags Ref Use Interface 224.0.0.0 192.168.41.75 U 1 0 eth0 # snoop -d eth0 224.0.1.1 Using device /dev/hme (promiscuous mode) dogbert -> 224.0.1.1 IP D=224.0.1.1 S=192.168.41.82 LEN=28, ID=24368 ratbert -> 224.0.1.1 NTP broadcast (Tue Aug 21 13:35:39 2001) catbert -> 224.0.1.1 IP D=224.0.1.1 S=192.168.41.92 LEN=28, ID=60455 dilbert -> 224.0.1.1 NTP broadcast (Tue Aug 21 13:36:43 2001)

  (replace "eth0" with the NIC device name connected to the multicast network.

• What is the year 2038 problem?
  UNIX epoch time is stored in a 4-byte signed integer. The maximum time is therefore 2,147,483,647 seconds after 1 January 1970. This translates into Tues. 19 January 2038 at 03:17:07 UTC (GMT). At 03:17:08, UNIX time wraps back 136 years to -2,147,483,648 seconds or Fri. 13 December 1901 at 20:45:52 UTC (GMT) and disaster strikes. Most software can't handle time before Thurs. 1 January 1970 00:00:00 UTC (GMT) and fail in various unexpected ways. On and after that time, many 32-bit programs running on UNIX systems (and therefore Solaris) will cease to function correctly.

  This does not apply to programs and software that have been upgraded to run in 64-bit mode. However, it's a good question to ask whether all (or even most) current (and near-future software) will be converted in time.

  There's a proposal for a new "struct xtime" in time.h for the new ISO C 200X standard. The struct xtime will have a signed 64-bit second counter, sec, and an unsigned 32-bit nanosecond counter, nsec. This handle time overflowing in 2038. It will also represent time from the big bang to well after the Sun's burnout. Also addressed in the proposal are other precision time problems, such as leap seconds and function reentrancy.

  For details and a thorough analysis of the problem, see Roger Wilcox's "The Year 2038 Problem". For a probable, realistic solution, see the proposed ISO C 200X time.h standard.

• How can I start ntpd with more verbose logging (for debugging)?
  First stop ntpd with /etc/init.d/ntpd stop and start ntpd directly with the -d option: ntpd -d Messages from ntpd will appear in syslog's messages file.

• Is ntpd software considered "munitions" by the U.S. government?
  Yes, and therefore requires a license to export outside of U.S. and Canada. This law also applies to re-export, Canadians, and to foreign branches or subsidiaries of U.S. companies.

  Why is ntpd software considered munitions? Because it contains the DES encryption algorithm (source file authdes.c). This is true even though DES code is easily available throughout the world and DES is easily cracked by brute-force attack (although triple DES can't be cracked). Anyway, to protect yourself and Sun legally, DES can be disabled in the makefile configuration. This is important to note if you're building or distributing another version of ntpd.

References

• NTP: Network Time Protocol http://www.ntp.org/ All the information you want to know about NTP from the source: Dr. Dave Mills and friends at the University of Delaware, who invented the NTP protocol and ntpd server. Includes pointers to commercial and non-commercial NTP software.
  • NTP FAQ Lots of troubleshooting information.

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