stale delta offers

1 files changed, 3 insertions, 0 deletions

diff --git a/docs/peers.md b/docs/peers.md
index 4775e85..fc4b6f1 100644
--- a/docs/peers.md
+++ b/docs/peers.md
@@ -172,6 +172,9 @@ other neighbours offer them too, and they would come once per offer. Offers that
 meanwhile wait; once the delta is in, the node syncs with those that offered, which then
 send only what is still missing. What a delta brought counts as known to its sender, as
 what its sync messages bring does: none of it goes back, by message or as a delta.
+An offer made before its sender heard what the node has now (one that came behind the
+chunks of the delta before it, say) would bring part of that again: such an offer isn't
+fetched; the node's next message tells the sender, which offers afresh if still needed.
 
 Towards a peer on a slow link the limit is lower: a message is offered as a delta if it
 would take more than 5 s at the throughput measured to that peer (`syncThroughput`,