[time-nuts] time-nuts Digest, Vol 99, Issue 111

Thu Oct 25 09:17:09 UTC 2012

Hello Magnus,

I know what you're talking about, I'm working for a company specialized in 
broadcasting (from studio's to stations to satellites...) and in this world correct 
timing is paramount, we live by the 1/25 second rythm and even less if you 
have to sync on a line in the image ;-).
Some time ago we were instaling a complete TV station and had huge problems
with image stability and also especially the correct starting time of a clip or transmission.
Nobody wants to start his newsreel at eg. 20:00:05;23... it must be 20:00:00;00
We were looking into this and noticed that the customers servers (Win!) where 
synced by SNTP, this is plain c..p!
Have a look @ http://technet.microsoft.com/en-us/library/cc773013(WS.10).aspx
Especially where it says:
"Important 
 The W32Time service is not a full-featured NTP solution that meets time-sensitive 
application needs and is NOT SUPPORTED by Microsoft as such. For more information, 
see Microsoft Knowledge Base article 939322, Support boundary to configure the 
Windows Time service for high-accuracy environments."

Also have a look @ http://support.microsoft.com/kb/939322
It says:
"We do not guarantee and we do not support the accuracy of the W32Time service 
between nodes on a network. The W32Time service is not a full-featured NTP solution
 that meets time-sensitive application needs. The W32Time service is primarily 
designed to do the following:
Make the Kerberos version 5 authentication protocol work.
Provide loose sync time for client computers.
The W32Time service cannot reliably maintain sync time to the range of 1 to 2 seconds. 
Such tolerances are outside the design specification of the W32Time service."

So it is...   1 to 2 seconds....!!!!!!!!

Our video playout servers are decent super stable units that use heaps of Xilinx FPGA's
for coding/decoding videostreams supervised by a mil-spec VXworks OS, it uses the 
so-called LTC for synchronising the playout, implemented mostly in hardware so
I did not suspect our machines. I did install a new TCG (TimeCode Generator) where
I also had heaps of problems with, I did debug the stuff together with the manufacturer's
R&D and finally got a perfectly synced station AND a Stratum-1 NTP (everything in
double with automatic failover, a requirement for a TV-station). (Thanks to lurking for 
years as a genetically predispositioned Time-Nut, my father was a watchmaker...So I 
knew more or less what a was talking about and could prove things thanks to my TBolt etc.)
Then I did install Meinberg NTP-client on every Win machine and all was suddenly 
perfectly running, everybody happy!
This also solved some frequent file versioning problems for storing different versions of 
videoclips especially in a mixed Win/Lin environment where Linux proved to be the 
more logical/strict way of implementation.

Another thing, being considered as the local video timenut a colleague called me from
Saudi Arabia where he was having timing problems on two locations spaced 700km. apart
where he had funny image jumps at the exact same time, both stations were synced by
each the same TCG with GPS option (same as above), could the americans jam the GPS
signals over there, somebody heard about this? It could be a real problem for us, we 
may need to use another method for station timing (Rb maybe, with some regular syncing
etc.)

Sorry for my long message but I don't often send timenut mail and this is a good example
of some real-life timenutting ;-)

I also have here a nice BeagleBone mini Linux board resting, where I would want to install 
a FreeBSD image on and implement a NTP with a promising GPS board from Adafruit,
something for the long and cosy winter evenings... :-)

Best regards,

Jacques Tiete

From: Magnus Danielson <magnus at rubidium.dyndns.org>
To: Time-Nuts <time-nuts at febo.com>
Subject: [time-nuts] Timing performance of servers
Message-ID: <50887008.3030609 at rubidium.dyndns.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Fellow time-nuts,

When spending time on a conference last week, I heard one interesting 
comment that they lost data due to bad timing on their Windows servers.

Now, I know that the standard Windows uses SNTP in order to achieve the 
goal of having the timing of the machines sufficiently aligned to allow 
Kerberos authentication. SNTP suffice for that, as it needs to be a 
handful of minutes in line.

If you need better performance than that, you should use NTP (and then 
download and install Meinbergs Windows-client for NTP).

Then again, I would point out that for this type of data, it would most 
probably be better served on a Linux box.

What should be a nice wake-up call for them would be a summation of how 
different strategies would give them clock precision of sufficient 
grade. So, does anyone know of such measurements presented anywhere?

There are bits and pieces, but the ideal for this case would be if they 
where collected in one page/paper.

This is an awareness thing, so that people can do a little more 
well-informed choices.

Cheers,
Magnus

------------------------------

Message: 6
Date: Wed, 24 Oct 2012 19:04:50 -0500
From: Edgardo Molina <xe1xus at amsat.org>
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] Timing performance of servers
Message-ID: <9A578007-FAB2-420E-BE25-6453F72E164D at amsat.org>
Content-Type: text/plain;	charset=iso-8859-1

Dear Mangus,

I will allow myself to share a comment on your thread. 

Timing on windows servers is not one of their plausible strengths. It was clearly pointed out during the SIM conference last week at CENAM. In fact there was an interesting discussion about the drawbacks when using NTP Windows based servers and all kind of NTP appliances compared to full size Linux based NTP servers. The example of what NIST is using nationwide for their servers set an example of good server hardware and linux to provide the nation's NTP pulse.

I haven't done any experiments with Windows for NTP services, still it could be interesting as to set a benchmark while comparing it to the Linux boxes.

I am currently trying out the Domain Time II NTP client from Symmetricom for the thesis. I have to come back to Symmetricom's Miguel Garc?a to decide on purchasing a Domain Time II NTP client kit.  How is the Mainberg NTP client different from the Symmetricom version? Have you tried both? If not I will be more than glad to help comparing both if you can help me pointing out the source for a demo version of Mainberg's software. Maybe then an objective review of both clients will be in order, I will be more than glad to do it or to test them against Windows NTP services, appliances and/or Linux NTP boxes. I have at least an example of those at the office.

			-13
Just my  2x10	cents.

Regards to you and the group,

Edgardo Molina
Direcci?n IPTEL

www.iptel.net.mx

T : 55 55 55202444
M : 04455 20501854