Siemens S7-300 Configuration Manual page 48

Configuring the Ethernet CP with STEP 7
3.3 Setting further CP properties
Option / input area
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48
Sending keepalives for
connections
File system (case-sensitive)
Meaning / effect
Here, you can set the interval at which keepalives are sent to the
partner of a communications connection. With this interval, you
specify the latest time after which the failure of a communications
partner will be detected.
For all connectionoriented services, the Ethernet CP is configured
so that keepalives are sent. This guarantees that connections are
terminated if a communications partner fails and that the
connection resources are released. The setting made here applies
to all TCP and ISO-on-TCP connections operated via the CP; a
connection-specific setting is not possible.
Range of values:
Default setting: 30 seconds
Disable keepalive: 0 seconds
Maximum value: 65535 seconds
Notes / recommendations:
Remember that the keepalive mechanism can keep underlying
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connections established (for example, an ISDN telephone
connection) although no user data is actually being transmitted.
If you do not want this, set the interval so high that the
underlying connection is terminated before a keepalive is sent
when there is no data traffic.
Avoid disabling keepalives using the setting "0". Otherwise you
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risk connections remaining established when the partner
station has failed that can no longer be terminated or re-
established.
On CPs with IT functions, activating this option allows you to
specify that the CP distinguishes between uppercase and
lowercase characters in the names of files for the RAM area.
Configuring and commissioning S7 CPs for Industrial Ethernet
Configuration Manual, 09/2013, C79000-G8976-C182-13