TWiki > Helpdesk > LinuxTimeServer	TWiki webs: AIX| Classes | HALBOD | HLUG | Helpdesk | Library | Main | Samba | TWiki |
	Helpdesk . { Home | Changes | Index | Search | Go }

Keeping Correct Time on Small Networks

• Yet Another D@#% Time HOWTO
• "Why would you want to do that ?"
• Disclaimer
• Case 1:  Microsoft® Windows workstations
  • Approach 1 — use a free commercial product
    • Pro's & Con's of Approach 1
  • Approach 2 — Use Free NIST Software
    • Pro's & Con's of Approach 2
  • Approach 3 — Use built-in Microsoft® facility
    • Pro's & Con's of Approach 3
• Scope & Assumptions
• References (Links)
  • Background
  • Eye Candy
  • Google Searches

Yet Another D@#% Time HOWTO (YADTH^©)

Here is a well intentioned example from the "father" of Internet time keeping:        http://www.eecis.udel.edu/~mills/ntp/html/build/quick.html Quick Start FAX test image for SATNET (1979). The baby panda was scanned at University College London and used as a FAX test image for a demonstration of the DARPA Atlantic SATNET Program and the first transatlantic Internet connection in 1978. The computing system used for that demonstration was called the Fuzzball . As it happened, this was also the first Internet multimedia presentation and the first to use NTP in regular operation. The image was widely copied and used for testing purpose throughout much of the 1980s. Last update: 01:01 AM UTC Saturday, March 20, 2004 For the rank amateur the sheer volume of the documentation collection must be intimidating. However, it doesn't take much to fly the ntpd daemon with a simple configuration where a workstation needs to synchronize to some server elsewhere in the Internet. The first thing that needs to be done is to build the distribution for the particular workstation and install in the usual place. The Building and Installing the Distribution page describes how to do this. • • • The panda is cute & its caption is historically interesting, but they are a distraction.  "For the rank amateur the sheer volume of the documentation collection must be intimidating." is great:  Easy to understand and too, too true.  "However, it doesn't take much to fly the ntpd daemon with a simple configuration ... " Oops! What's a daemon?  Just lost the average user. . .

This paper will present some simple solutions:  easy to understand, easy to implement. 
I will present 3 cases:  Microsoft® Windows workstations, a Linux Time Server, & GNU/Linux workstations. 

"Why would you want to do that ?"

• You're tired of setting your computers' clocks
• You're tired of forgetting to check your computers' clocks
• You're tired of your computers' clocks being 5 to 30 minutes off
• You want your your computers' clocks to be the best time "in the house"
• You want your your computers' clocks to all be the same
     (So that time stamp comparisons are valid)
• It's a cool thing to do. 
     ("Because I can." / "Because it was there.")

• http://www.ntp-systems.com/products_timekeeping.asp    1st paragraph
• http://www.eecis.udel.edu/~ntp/ntpfaq/NTP-s-def.htm#AEN1223
     (link should go to "4.1.3. Why should Time be synchronized?")

Disclaimer

1. No Warranty — If your system breaks, you get to keep the parts. :-)
2. Really No Warranty — I haven't finished learning about this yet. ;-)
3. Double No Warranty — This is a work in progress, all of the little I know isn't up here yet. :^o

Case 1:  Microsoft® Windows workstations

Approach 1 — use a free commercial product

• http://www.symmttm.com/download_symmtime_access.asp

• http://216.26.171.146/SymmTime2004.exe

Pro's & Con's of Approach 1

• Free. 
• Easy. 
• Works on all versions of Microsoft® Windows from 95 on. 
• Works with a local time server if & when you install one. 

• Propietary — may be unavailable in the future. 
• Requests personal information as a condition of download. 
• Not  Open Source

Approach 2 — Use Free NIST Software

• ftp://time.nist.gov/pub/daytime/nistime-32bit.exe — the 32 bit version (Win 95 up)
• ftp://time.nist.gov/pub/daytime/nistimew.exe — the 16 bit version (Win 3.1)
• http://boulder.nist.gov/timefreq/service/its.htm the Internet Time Service (ITS) web page

Pro's & Con's of Approach 2

• Free. 
• Easy. 
• Works on all versions of Microsoft® Windows from 95 on. 
• Win 3.1 version also available. 
• Government sponsored — unlikely to disapear. 
• Requests NO  personal information. 
• Source Code available !!!

• Will NOT  work with a local time server if & when you install one. 

Approach 3 — Use built-in Microsoft® facility

Pro's & Con's of Approach 3

• Already paid for. 
• Built-in — no download. 
• Works with a local time server if & when you install one. 

• Not easy. 
• Different techniques for different versions of Microsoft® Windows . 
• Not clear if available for Win 95. 
• Not  Open Source

. 

It is also desirable (another "Good Thing™") to have no more than 2 of them getting their time from the 'net. 

1. Because more than 2 is a waste of other peoples' resources, and therefore impolite. 
2. Because more than 2 may be a waste of your own resources, and therefore stupid. 

Scope & Assumptions

• A broadband connection —
       I have Earthlink over Time-Warner
• A "broadband router" —
       I have an SMC Barricade
• At least 1 GNU/Linux (potential) server —
       I have a Web server, and plan to both a file server & a dedicated firewall
• The GNU/Linux server has a fixed IP address —
       Each permanent host on my LAN has a designated IP, my SMC Barricade is my DHCP server, but it is set to always assign each permanent host its own designated IP
• At least 2 workstations running whatever OS you like or are stuck with —
       We have a Win 98SE, a W2k Pro, & "the Penguin" which runs my Linux du jour, currently Debian Sarge.  We have no Mac's or XP boxen. 
• 1 second accuracy is just fine

This document does not  cover: 

• LAN's with an intermittent connection to the 'net —
       like dial-up, or possibly PPPoE i.e. SBC/Yahoo
• LAN's with no available GNU/Linux server or potential server
• Win 95, Mac OS - any flavor, Win XP —
  • Win 95 may or may not be capable of referencing a local time server
  • Mac OS X is BSD based & should be capable of using a local time server
    earlier Mac's, I have no idea
  • I don't use XP, but it is almost the same as W2k & I link to the instructions for it
• Serving Time to the 'Net in addition to the LAN
• Milli-second accuracy or time reference traceability (required of some businesses)

1. . 

• —
      

References (Links)

1. Time Precision HOWTO: 
   Managing Accurate Date and Time
   Avi Alkalay
   http://tldp.org/HOWTO/TimePrecision-HOWTO/index.html`
   This is the "Bible" on the subject as well as the ispiration and major source for this paper
   
   • 4. Accurate Global Time Synchronization
     http://tldp.org/HOWTO/TimePrecision-HOWTO/ntp.html
     is almost mandatory reading
     
   • 3. The Correct Settings for Your Linux Box
     http://tldp.org/HOWTO/TimePrecision-HOWTO/set.html
     is highly reccommended
     `
     `
     `
     
2. pool.ntp.org: public ntp time server for everyone
   http://www.pool.ntp.org/ — This is the wonderful public server pool
   http://www.pool.ntp.org/#use — and how to use it ("How do I use pool.ntp.org?")
   
   
3. The Windows Time Service
   By Shala Brandolini and Darin Green, Microsoft Corporation
   Published:  April 2001
   Summary:  http://www.microsoft.com/windows2000/techinfo/howitworks/security/wintimeserv.asp
   Download:  http://download.microsoft.com/download/2/0/f/20f61625-7b2a-4531-b007-1c714f1e51b7/wintimeserv.doc
   Note:  This is a pain to read as a .doc, so I converted it to .pdf using OpenOffice.org
   
   
4. Windows Time Service Issues
   Greyware Automation Products, Inc.
   discussion from a vendor trying to sell a (rather expensive) product, some good background
   http://www.greyware.com/software/domaintime/product/w32time.asp
   
   

Background

• NIST — the NIST site is fascinating, but  none of it is directly applicable to the methods described here
  • Home:  http://www.boulder.nist.gov/timefreq/index.html
  • Welcome:  http://www.boulder.nist.gov/timefreq/general/about.html
  • Set Your Computer Clock Via the Internet
    NIST Internet Time Service (ITS)
    http://www.boulder.nist.gov/timefreq/service/its.htm
    

This last one is especially seductive, but it contains NO Linux/UNIX instructions, & everything else is geared to having all your hosts connecting directly to external servers ... exactly what we are NOT doing here.

• If you like it long & technical, check out this thread about time server abuse:
  http://groups.google.com/groups?threadm=3E2DBFF7.F9A51614%40udel.edu

Eye Candy

• NIST On-line Clock Displays
  Animated:  http://www.time.gov/timezone.cgi?Central/d/-6/java
  Static:  http://www.time.gov/timezone.cgi?Central/d/-6

• http://www.timeanddate.com/

• http://www.symmttm.com/download_symmtime_access.asp

• http://www.ntp-systems.com/popups/images/network_diagram.gif

Google Searches

• nist time:  http://www.google.com/search?num=100&hl=en&lr=lang_en&ie=UTF-8&safe=off&q=nist+time&btnG=Search

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters]
"LocalNTP"=dword:00000000
"Period"="SpecialSkew"
"type"="NTP"
"ntpserver"="192.168.xxx.yyy"
"Adj"=dword:0001872c
"msSkewPerDay"="-1728.0000"

# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 LOCAL(0)        LOCAL(0)         5 l   59   64  377    0.000    0.000   0.015
+<myisp>.com     172.20.0.1       3 u  601 1024  377   39.950  -21.081   0.896
*<anuplink>.com  24.30.206.134    2 u  495 1024  377   17.719  -29.706   0.305
+<reference>.org ntp-cup.externa  2 u  542 1024  377   90.797  -22.410   3.604

The "*" in the first column means its favorite is the Stratum 2 (col 3, "st") server with the low jitter.  Low jitter is good jitter. 

The "+"'s in the first column mean the other two are working fine (ntp "likes this server"). 

The polling interval for the 3 external servers (col 6 "poll") has reached the default maximum (1024).  This is also good — it means that the clock is well sync'ed and the ntp daemon is in maintenamce mode. 

The "reach" (col 7) for all servers is 377, which is both maximum & perfect.  It means that the ntp daemon has not failed to reach any of them in its last 8 tries. 

"This is an octal representation of an array of 8 bits, representing the last 8 times the local machine tried to reach the server. The bit is set if the remote server was reached."

BTW, the LSB (least significant bit) seems to represent the most recent attempt. 

If your binary arithmetic is rusty, 377₁₀ = 11111111₂ = 2^8 — i.e. no recent failures. 

And don't forget: 
There are 10 kinds of people in the world ... 
Those who understand binary and those who don't. 

LinuxTimeServerDrafts