libnodave, which protocol is used?

In the Siemens manual "SIMATIC NET S7-CPs for Industrial Ethernet Configuring and Commissioning", Manual Part A - General Application it is specified at page A-298 a certain ISO-TCP format for the PDU's of FETCH and WRITE.

Now my question: Even though libnodave works very well, I did not find the same format in the Ethernet sequences. I can see the ISO 8073 header, but the Siemens headers (starting with 'S5') seem to be missing. Why would that be, does libnodave use another protocol?

First I have to warn that I am not an expert in Libnodave.

But Fetch/Write is a protocol mainly used with S5, and as far as I understand an S7 can only respond to incoming Fetch/Write. An S7 cannot initiate Fetch or Write itself. So Fetch/Write is only partially supported in S7 in order to achieve some compatibility with older S5 systems.

Unless you intend to work with older S5 systems, Fetch/Write should be forgotten.

Indeed, as I understand, we will only use the PLC's as passive, so they will not have the initiative.

Still my question remains, why can't we find those Siemens codes in the sequences that are exchanged? Apparently the protocol used is entirely different than what the manual says.

Are you going to connect to an S7 or to an S5 ?

They are all S7.

Then you will not be using Fetch/Write mechanism.
Forget that document that you have found.