docs: how long a broken path takes to see, with PINGs taking turns

Review 4, 1258's note: the glossary says that a path whose way out broke while the
peer's PINGs still come is found by this node's own unanswered PINGs, which with the
turns come every one to two intervals, up to twice as long as before, and what still
finds it at once.

1 files changed, 5 insertions, 1 deletions

diff --git a/docs/glossary.md b/docs/glossary.md
index e8ccdee..fd165f1 100644
--- a/docs/glossary.md
+++ b/docs/glossary.md
@@ -95,7 +95,11 @@ STATUS_REPLY instead, carrying the sender's heads (or a digest of them and some
 them), epoch and readiness. The two sides of a pair take turns; the one that **leads**
 the pair sends the first. The paths layer's PINGs of a path take turns with the peer's
 too, so each side measures a path's round trip every other interval: a shorter
-`--keepalive` measures more often.
+`--keepalive` measures more often. A path whose way out broke while the peer's PINGs
+still come is found by this node's own unanswered PINGs, three in a row, which then
+come every one to two intervals: up to twice as long as without the turns. Unanswered
+traffic or a failed send pings at once, and the peer finds it by its own missing
+PONGs.
 
 **initial sync**: a joining node's first complete sync. It's **caught up** once a ready
 peer with non-empty heads has nothing left that it lacks.