Full Disclosure mailing list archives
RE: Windows Time Synchronization - Best Practices
From: "joe" <mvp () joeware net>
Date: Fri, 22 Oct 2004 09:28:58 -0400
So right off the bat you know you are sacrificing something. Why settle for less than the best when the best is free?
Two reasons. Say you don't need the full feature set of NTP and/or you manage hundreds of thousands of machines globally and you don't want to have to add something additional. Microsoft Windows Domains are to my knowledge, the only systems out of the box dependent on kerberos. Time is extremely important for kerberos and extremely important for Windows Domains. I have seen many examples of the Windows SNTP implementation working perfectly fine across very large companies with several hundred thousand machines with no need to install/manage any other software. These environments fall into the default Windows Domain configuration of the members talking to their domain controller for time and their domain controller going up the chain until you get to the forest root PDC which takes its time from some defined time source(s). Even if the defined time source isn't correct the entire forest has the same wrong time which is actually more important for a majority of the work done in a domain than having the exact right time. Additionally I managed a Windows AD Domain environment with some 200,000+ Windows machines for 4 years and almost never had to think about time because the builtin Windows time system worked. The points I had to think about it were when someone took it into their own hands and set their own time sources either with the Windows software or with third party software and that time source wasn't accurate. If the time is wrong across an entire forest that is almost certainly the fault of the admins configuring the DCs or the vendor consultants for the company not knowing what they are talking about - not a failing in SNTP. If you take on one-off home PCs, people can do whatever they want for time. Managing additional software on your home personal PC is extremely different from doing it for tens or hundreds of thousands of machines across the world. Additionally, if your home PC time is different from some other machine, it usually won't impact your ability to logon to the local machine because you are using the local PCs IDs though it could impact various other secure transactions with other systems.
Never heard of time.microsoft.com being down or incorrect.
Me neither, but it has been unreachable. Since the original requestor was from Brazil I would think that reachability would be an issue for him.
time.microsoft.com is simply a default if nothing else is set. Change it, that is extremely easy.
Yeah, but you are still stuck with only ONE server, you are stuck with
SNTP
and you have almost no way to tell if the time daemon is doing the right
thing. Incorrect on all accounts except you are using SNTP and you still haven't shown a valid reason why that is bad. joe -----Original Message----- From: full-disclosure-admin () lists netsys com [mailto:full-disclosure-admin () lists netsys com] On Behalf Of Gary E. Miller Sent: Thursday, October 21, 2004 5:47 PM To: Cushing, David Cc: full-disclosure () lists netsys com Subject: RE: [Full-disclosure] Windows Time Synchronization - Best Practices -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Yo David! On Thu, 21 Oct 2004, Cushing, David wrote:
In my experience NTP will work a lot better for you than Windows Time server.Windows time service uses SNTP.
SNTP is RFC 2030, It says: "SNTP can be used when the ultimate performance of the full NTP implementation described in RFC-1305 is not needed or justified." So right off the bat you know you are sacrificing something. Why settle for less than the best when the best is free? RFC 2030 Continues: "It is strongly recommended that SNTP be used only at the extremities of the synchronization subnet. SNTP clients should operate only at the leaves (highest stratum) of the subnet and ..." "The full degree of reliability ordinarily expected of primary servers is possible only using the redundant sources, diverse subnet paths and crafted algorithms of a full NTP implementation. " Seems to me that rules out using it to connect to the stratum 1 in Seattle, WA from Brazil.
The protocol is robust and you are not dependent on the single point of failure called: time.microsoft.com.Never heard of time.microsoft.com being down or incorrect.
Me neither, but it has been unreachable. Since the original requestor was from Brazil I would think that reachability would be an issue for him. Last time I was monitoring reachability to Brazil there were often outages and bottlenecks to there from the US.
You can use 'net time' or regedit to change it. http://www.microsoft.com/windows2000/docs/wintimeserv.doc
Yeah, but you are still stuck with only ONE server, you are stuck with SNTP and you have almost no way to tell if the time daemon is doing the right thing. With NTP you can designate a local master that gets it's time from a diverse set of sources. It is easy to verify and monitor it's proper functioning. Then you can redistribute it to your local hosts. Contrary to what some may believe, accurate time is very important to security. One time keys, like S/Key, depend on accurate time for their functioning. Any stronge encryption scheme, like IPSec, needs a good clock at both ends to default antireplay attacks When debugging a major system crash, involving many routers, switches, hosts, etc. it is important to have well synced clocks to determine first failure. Stick exchanges require members to use accurate clocks to help prevent fraud. Etc... RGDS GARY - --------------------------------------------------------------------------- Gary E. Miller Rellim 20340 Empire Blvd, Suite E-3, Bend, OR 97701 gem () rellim com Tel:+1(541)382-8588 Fax: +1(541)382-8676 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (GNU/Linux) iD8DBQFBeC5w8KZibdeR3qURAjDhAJ9kue1cKLMrcVykpL4P03XyCnuB+ACbBL4b mNs+1jkUA470nRGx6ZXPGGA= =9SAK -----END PGP SIGNATURE----- _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
Current thread:
- RE: Windows Time Synchronization - Best Practices, (continued)
- RE: Windows Time Synchronization - Best Practices Todd Towles (Oct 19)
- RE: Windows Time Synchronization - Best Practices Keith Pachulski (Oct 19)
- RE: Windows Time Synchronization - Best Practices Cushing, David (Oct 21)
- RE: Windows Time Synchronization - Best Practices Gary E. Miller (Oct 21)
- RE: Windows Time Synchronization - Best Practices Frank Knobbe (Oct 21)
- Re: Windows Time Synchronization - Best Practices Micheal Espinola Jr (Oct 22)
- Virus/Trojan trying to connect external:445 and 212.175.149.149.6667 Murat Bicer (Oct 22)
- Re: Virus/Trojan trying to connect external:445 and 212.175.149.149.6667 darren windham (Oct 22)
- Re: Windows Time Synchronization - Best Practices Gary E. Miller (Oct 24)
- Re: Windows Time Synchronization - Best Practices Andrew Farmer (Oct 25)
- RE: Windows Time Synchronization - Best Practices Gary E. Miller (Oct 21)
- RE: Windows Time Synchronization - Best Practices joe (Oct 22)