From 1ae421e876d87a3f9936f5375b7ce29a62aeefe4 Mon Sep 17 00:00:00 2001
From: Thomas Kolb <cfr34k-git@tkolb.de>
Date: Sat, 21 Sep 2024 00:55:25 +0200
Subject: [PATCH] doc: add state diagrams

---
 doc/hamnet70.adoc | 69 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/doc/hamnet70.adoc b/doc/hamnet70.adoc
index 031bd3f..0a05993 100644
--- a/doc/hamnet70.adoc
+++ b/doc/hamnet70.adoc
@@ -524,6 +524,75 @@ msc {
 }
 ....
 
+=== State Diagrams
+
+This section documents state diagrams for the digipeater and the clients.
+They are only informational; different implementations are possible and allowed as long as the procedures defined by the <<_message_sequence_charts,message sequence charts>> are obeyed.
+However, the state diagrams shown here reflect the reference implementation.
+
+==== Connection State Diagram
+
+[graphviz,format=svg,svg-type=interactive,scale=1.0]
+.Connection state diagram
+....
+digraph connection {
+	uninitd [label="Uninitialized"];
+	connecting [label="Connecting"];
+	wait_client [label="Wait for\nclient"];
+	estab [label="Two-way communication\nestablished"];
+	closed [label="Closed"];
+
+	uninitd -> connecting [label="Connection request\nsent [client]"];
+	uninitd -> wait_client [label="Connection request\nreceived [digipeater]"];
+
+	connecting -> estab [label="Connection\nacknowledgement sent"];
+	wait_client -> estab [label="Connection\nacknowledged"];
+
+	connecting -> closed [label="Timeout"];
+	wait_client -> closed [label="Timeout"];
+
+	estab -> closed [label="Disconnect/Timeout"];
+	closed -> uninitd [label="State erased"];
+}
+....
+
+==== Digipeater Connection Multiplexing
+
+[graphviz,layout=neato,format=svg,svg-type=interactive,scale=1.0]
+.Handling of multiple connections at the digipeater
+....
+digraph multiclient {
+	overlap=false;
+
+	idle [label="Idle"];
+	send_beacon [label="Send Beacon"];
+	accept_new [label="Check for\nnew clients"];
+	check_conn [label="Check connection timers"];
+	send_to_client [label="Send queued packets\nto client"];
+	receive_from_client [label="Receive packets\nfrom client"];
+	check_timeout [label="Check connection\ntimeout"];
+	reset_timeout [label="Reset connection\ntimeout"];
+	close_conn [label="Close\nconnection"];
+
+	idle -> send_beacon [label="Beacon timeout\nexpired"];
+	send_beacon -> accept_new;
+	accept_new -> idle;
+
+	idle -> check_conn [label="Any contact\ntimer expired"];
+	check_conn -> send_to_client [label="Contact timer\nexpired"];
+	send_to_client -> receive_from_client;
+	receive_from_client -> reset_timeout [label="Packets received"];
+	reset_timeout -> check_conn;
+
+	receive_from_client -> check_timeout [label="Nothing received"];
+	check_timeout -> check_conn [label="No timeout yet"];
+	check_timeout -> close_conn [label="Timed out"];
+	close_conn -> check_conn;
+
+	check_conn -> idle [label="All expired\nconnections handled"];
+}
+....
+
 == Higher Layer Protocols
 
 [appendix]