| Support > Library > FAQs and Troubleshooting > Number of NTP clients
|
|
FAQ's and Troubleshooting
Q. What is the number of clients that can be served by a NetClock time server?
A.
The 9200 series NetClock time servers can serve about 4,000 NTP requests per second -- an order of magnitude more than the previous generation 9100 series. Hundreds of thousand NTP clients can be managed by one time server depending on sync interval and the distributions of the requests. See below for details.
A 9200 Series Model can handle around 4,000 NTP requests per seconds in Unicast mode. The number of clients on the network and all subnets of the immediate network that can synchronize to the NTP Time Server at this level is a statistical value that is determined by three main factors. These factors are:
1) The number of NTP requests per second the Time Server can respond to.
2) The length of the poll interval for the NTP client software program that is running on the network PCs.
3) How evenly distributed (across the network) that the poll interval schedule is for all of the PCs.
Factor number 1 -The higher the number of requests per second that the NTP Time Server can provide, the higher the number of clients that can synchronize to it.
Factor number 2 -The NTP client program is going to have a poll interval at which it requests time from the NTP Time Servers (how often it synchronizes to the Time Sever). This interval may be a fixed value (like once every 5 minutes for example). Some NTP client programs have a user-definable set value that is always used.
Some common examples of poll interval:
* Windows 2000 by default only synchronizes every 8 hours (every 28,800 seconds)
* Windows XP (pre-service pack 2)only syncs by default every 7 days (every 604,000 seconds) but this can be changed to sync once an hour (every 3600 seconds).
* Windows 2003 and XP (with service pack 2 installed) polls about every 15 minutes (every 900 seconds)
* PresenTense NTP software for Windows can sync up to once-per-minute based upon a drop-down value (every 60 seconds)
* Other programs like the NTP4 program for UNIX PCs have a variable poll interval which occurs within the user-definable minimum and maximum poll interval values. The poll interval will occur more often when it first starts up but slows down over time as the service stabilizes from startup. For NTP4, by default, the minimum poll interval is once-per-minute and the maximum poll interval is once every 17 minutes. The longer the duration of time between each poll interval is for each of the PCs, the more clients that are able to synchronize to the Time Server.
Factor number 3 - At what specific time the poll intervals are scheduled to occur also determine how many clients can be synchronized from the NTP Time Server. Most client programs will automatically stagger the time at which they will synchronize to the Time Server. They will “schedule” the poll interval to occur at various times of the day- not based on a specific time of the day (They don’t schedule the interval to occur on all PCs at 8:00:00AM every day, for example because this would cause all of the PCs to try at the same time to receive the NTP packets). One PC may poll the NTP Time Server at 8:04:32 AM and the next PC may poll at 8:04:35 AM. This is intentionally done to prevent the PCs from all having to poll the Time Server at the exact same time. The poll interval on most client programs is scheduled based upon the time that the service is started so this becomes the method to stagger when the PCs poll the Time Server.
The formula for calculating the statistical number of clients that can synchronize to the Time Server is based upon these two factors and the number of NTP requests the NTP time Server can handle in any given second. The formula is used to calculate for the worst-case number of clients that can synchronize to the Time Server at any one particular second.
The formula is: Number of clients = (packets per second) X (number of seconds between the poll interval of the clients).
(Where the “packets per second” for the 9200 series is about 4,000)
Examples of this formula:
* Number of Windows 2000 PCs 4000 X 28,800 = 115,200,000 PCs per network.
* Number of Windows XP (SP2)/2003 PCs 4000 X 900= 3,600,000 PCs per network.
* Number of UNIX PCs running NTP Version 4 client software at the minimum interval of 1 minute 4000 X 60= 240,000 PCs per network.
* Number of UNIX PCs running NTP Version 4 client software at the maximum interval of 17 minutes 4000 X 1,020= 4,080,000 PCs per network.
« Go Back to FAQ's
|
|
|
|
|
|
|
|
|
|
|
|
|