revision of SECoP documentation

- created secop_v2017-09-14.rst, based on the GoogleDocs
  SECoP Preliminary V2016-11-30 (rc 2)
- this Document is supposed to contain the full SECoP standard
- created SECoP issues
- moved everything else to "outdated" (kept for reference)

Change-Id: I87d69d1846fc4ed55f1c78b22fd4650d8550152b
Reviewed-on: https://forge.frm2.tum.de/review/16573
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>

doc/source/protocol/issue_7.rst

@@ -0,0 +1,24 @@
+SECoP Issue 7: Time Synchronization (under discussion)
+======================================================
+
+As a SECoP server and a SECoP client might not run with a common clock,
+the SECoP client should be able to correct for time slips.
+
+The recommended mechanism is (proposal by Markus):
+
+After connecting to a server, the client records its internal time before sending
+a ping request.
+
+If the pong request does not contain a timestamp,
+the client knows, that the SEC node does not provide timestamps and
+therefore it has to create timestamps on the time of reception of messages.
+
+If the returned timestamp lies between the time the ping message was sent and the
+time the pong message was received, it does not need to correct the timestamps.
+
+If not, the average of the 'ping' time and the 'pong' time is calculated and
+the difference to the received timestamp is used for correcting further
+timestamps.
+
+On the meetings in Berlin and Garching in 2017 it was proposed to put this into
+the standard, the exact wording has to be decided.