diff --git a/docs/tcp_replication.md b/docs/tcp_replication.md

index ba9e874d07..e3a4634b14 100644
--- a/docs/tcp_replication.md
+++ b/docs/tcp_replication.md
@@ -209,7 +209,7 @@ Where `<token>` may be either:
  * a numeric stream_id to stream updates since (exclusive)
  * `NOW` to stream all subsequent updates.
 
-The `<stream_name>` is the name of a replication stream to subscribe 
+The `<stream_name>` is the name of a replication stream to subscribe
 to (see [here](../synapse/replication/tcp/streams/_base.py) for a list
 of streams). It can also be `ALL` to subscribe to all known streams,
 in which case the `<token>` must be set to `NOW`.
@@ -234,6 +234,10 @@ in which case the `<token>` must be set to `NOW`.
 
    Used exclusively in tests
 
+### REMOTE_SERVER_UP (S, C)
+
+   Inform other processes that a remote server may have come back online.
+
 See `synapse/replication/tcp/commands.py` for a detailed description and
 the format of each command.
 
@@ -250,6 +254,11 @@ and they key to invalidate. For example:
 
     > RDATA caches 550953771 ["get_user_by_id", ["@bob:example.com"], 1550574873251]
 
+Alternatively, an entire cache can be invalidated by sending down a `null`
+instead of the key. For example:
+
+    > RDATA caches 550953772 ["get_user_by_id", null, 1550574873252]
+
 However, there are times when a number of caches need to be invalidated
 at the same time with the same key. To reduce traffic we batch those
 invalidations into a single poke by defining a special cache name that