Persistent Serial Tunneling (Pst) Functionality; Figure 1-3. Persistent Serial Tunneling - Siemens A53457 Installation & Maintenance

1.5

PERSISTENT SERIAL TUNNELING (PST) FUNCTIONALITY

In a Persistent Serial Tunneling (PST) application (see Figure 1-3), the WAG operates as a modem
that enables serial devices to communicate via the LAN. The WAG converts the serial data into
Ethernet packets and transmits the information onto the LAN. A second WAG at the other end
converts the information back to serial data for use by the other serial device.
WAGs are configured to communicate in pairs as illustrated above. When one or both of the
WAGs in the paired system is configured with the "Persistent Serial Tunnel" IP address of the other
WAG, it will attempt to establish a Transmission Control Protocol (TCP) connection to the other
WAG at that IP address.
For most applications, only one WAG is configured to establish the connection, however, if both
are configured to do so, the Tunnel will still be established. Typically the WAG that is physically
located in the office is configured to establish the connection to the other WAG which may be in
the field.
When the system is powered up, the WAG will attempt to establish the PST TCP connection to the
WAG's "Serial Telnet" port number (which defaults to 10023).
In addition to other typical configuration requirements for the WAG, in general, the following are
required for PST to work:
1. Both WAGs must be configured to have a serial interface format of RAW data mode.
2. One or both of the WAGs in the paired system must be configured with the IP address of
the other WAG.
3. Both WAGs must be configured with the same Serial Telnet port number (usually 10023).
4. Both WAGs must also have that same Serial Telnet port number configured in its list of
four TCP port numbers.
Document No.: COM-00-05-16
Version: C.1

Figure 1-3. Persistent Serial Tunneling

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DESCRIPTION
June 2006, Revised June 2014