29 September 2021
Within my APC Network Management Card, what does the Force Negotiation setting accomplish?
- Network Management Card 1 (NMC1) - AP9617, AP9618, AP9619
Devices with an embedded Network Management Card 1 include (but are not limited to): Metered/Switched Rack PDUs (AP78XX, AP79XX), Rack Automatic Transfer Switches (AP77XX, Environmental Monitoring Units (AP9320, AP9340, NetBotz 200)
- Network Management Card 2 (NMC2) - AP9630/AP9630CH, AP9631/AP9631CH, AP9635/AP9635CH
Devices with an embedded Network Management Card 2 include (but are not limited to): 2G Metered/Switched Rack PDUs (AP86XX, AP88XX, AP89XX), Certain Audio/Video Network Management Enabled products.
- PowerChute Network Shutdown
- Users configuring PowerChute Network Shutdown in conjunction with their APC Network Management Card for graceful shutdown options
- All Network Management Card firmware versions
Explanation for this setting and why you may need to selected it are listed below.
The Force Negotiation
setting in the Network Management Card relates to PowerChute Network Shutdown clients and the maximum required delay needed for their shutdown. A safe shutdown time for the UPS is calculated differently for a UPS device with outlet groups compared to a UPS without outlet groups.
The Maximum Required Delay setting is going to be the low battery signal time/low battery duration value by default. Low battery signal/low battery duration is a value set only on the UPS and does not look at external variables such as PowerChute Network Shutdown clients.
- For a UPS without outlet groups, the shutdown time is the Maximum Required Delay value on the NMC shutdown screen plus two minutes plus the [configurable] shutdown delay for the UPS.
- For a UPS with outlet groups, the shutdown time is the Power Off Delay value on the NMC outlet groups screen. (This option is not available with all UPS devices).
Note: Smart UPS Modular devices, with a SKU beginning with SUM, utilize bullet point #1's behavior, not #2 even though they have outlet groups.
For both types of UPS devices, the shutdown time is negotiated by the NMC interacting with PowerChute Network Shutdown (PCNS).
Use the Force Negotiation option when you change or add a PCNS client to re-gauge the shutdown time. PCNS starts with the NMC Low Battery Duration value, compares it to its own total shutdown duration and, if the battery duration time is too low, tells the NMC to increase values in #1 and #2 below to the PCNS shutdown required time plus 70 seconds.
- Without outlet groups, the Maximum Required Delay.
- With outlet groups, the Power Off Delay for the outlet group supplying power to the PCNS server. (Note: The value in PCNS for VM Shutdown/vApp shutdown will affect UPS Outlet Group Power Off delays, if applicable.)
The 70 seconds mentioned is the default OS shutdown time for PCNS. PCNS never changes the NMC Low Battery Duration field value. With PCNS v3.X, the Maximum Required Delay value is never used by the NMC for a UPS with outlet groups.
The PCNS Required time = the shutdown delay plus the shutdown command file duration. When the 70 seconds is added, the time is always rounded up to the nearest minute. For example, a total of 3 minutes, 50 seconds is rounded up to 4 minutes; a total of 2 minutes is still rounded up to 3 minutes.
Keep in mind that the value doesn't update immediately. This is due to the fact that the network management card is polling the minutes Network Shutdown clients and needs to time to adjust. It may take as low as a minute, and as high as six to seven minutes. A quicker way of forcing negotiation is by rebooting the card.
Also, note that the network management card will take the greater of the two values (low battery setting vs. minutes Network Shutdown required shutdown delay). If you set the command line shutdown of 8 minutes on the client but have a low battery of 10 minutes, the card will take the 10 minute value as the max required delay.
Your PCNS operating system shutdowns and UPS and outlet group turn offs follow the sequence below (illustrated with graphics), with the On Battery event used as an example.
With an outlet group turn off, the steps vary as indicated in the text below, and in the separate graphic.
1. PCNS reports that the UPS is on battery. Before initiating a shutdown, PCNS waits the amount of time configured by the user with the Shut down the system only when the event lasts this long (seconds) field, available through the Configure Events page.
2. The Command Files Run. When the Run Command File action has been configured by the user on the Configure Shutdown page, the specified command file executes. Its execution time is determined by the field named The command file needs this much time to complete (seconds).
Any event command file set up on the Configure Events page for On Battery executes concurrently. It begins after the event delay time (set up in Run the command file only when the event lasts this long (seconds)). This event delay time plus the event command execution time (set up in The command file needs this much time to complete (seconds)) must not be greater than the execution time for the Configure Shutdown command file mentioned in the previous paragraph.
Note: The execution of this event command file is not represented in the graphic below.
3. The PCNS server operating system issues a shutdown command. There is a pause of 70 seconds until it executes. This is made up of shutdownDelay (10 seconds) and Shutdown Delay (60 seconds) in the ShutdownCommandDuration file. Do not change these values unless you have a reason for doing so.
4. The UPS or Outlet Group Turn Off Begins. The UPS or outlet group initiates its shutdown. The delay time calculation depends on what is being turned off.
It waits the amount of time indicated by one of the following, whichever is greater:
Low battery duration:
Configure this value in the Network Management Card (NMC) web user interface.
The command file needs this much time to complete (seconds):
Configure this value in PCNS on the Configure Shutdown page.
A Switched Outlet Group waits its Power Off Delay time, set in the NMC.
A Main Outlet Group wait its Power Off Delay time plus the longest Power Off Delay time for any of its Switched Outlet Groups.
5. A 2-minute delay. This is built-in and cannot be changed by the user. This delay is NOT relevant to an outlet group turn off.
6. Sleep sequence starts. The UPS starts its sleep sequence.
For all outlet groups, the sleep command is issued and this is the end of the turn off sequence. The outlet group turns on when AC utility power is restored. You cannot configure it to stay off.
7. UPS Shutdown Delay. Configure this value for the UPS using the NMC user interface.
8. Turn Off. The UPS is turned off.
By default, the UPS will turn on again when power is restored and the battery has re-charged. You can configure the UPS to turn on automatically or manually when power returns after a power failure. An automatic turn-on will restart the equipment that the UPS is supporting. Set this parameter in the NMC user interface by using the On-Battery Shutdown Behavior field.
Note: For events other than On Battery and Low Battery, the UPS or the outlet group is turned off and remains off.
Below is also a shutdown timeline that may be useful for both UPS and Outlet Group references. This is taken from the PowerChute Network Shutdown v3.0 help file.