predecessors go along

1 files changed, 5 insertions, 1 deletions

diff --git a/docs/peers.md b/docs/peers.md
index 4ee3c16..9ef570b 100644
--- a/docs/peers.md
+++ b/docs/peers.md
@@ -361,7 +361,11 @@ doesn't carry them again. Without that, with writers in turn, each change coming
 another tree, the node's view of a neighbour stays as of its last message to it, and
 the next carries all it got since, nearly all of it brought by the neighbour's other
 parents (with 50 nodes and writers in turn, about ten changes per message, one of them
-new). Should one lack them after all, it asks, as above.
+new). Should one lack them after all, it asks, as above. But what the node passes on
+to a child carries those of them the passed-on changes build on, if counted so within
+the last 2 s: with writers in turn each change builds on the last writer's, which may
+still be on its way along another tree, and the child would have to ask for it, a round
+trip later.
 
 As nobody waits for these answers, messages overtake each other on slow links. Three
 things keep that from sending changes twice (`document::sync`):