diff --git a/metropolis/proto/common/common.proto b/metropolis/proto/common/common.proto
index 07ff460..46bd08f 100644
--- a/metropolis/proto/common/common.proto
+++ b/metropolis/proto/common/common.proto
@@ -132,6 +132,9 @@
     // listening for gRPC, and role-specific services like etcd and
     // Kubernetes).
     string external_address = 1;
+    // timestamp is an epoch number associated with the last status update.
+    // It's set with a nanosecond granularity.
+    int64 timestamp = 2;
 }
 
 // The Cluster Directory is information about the network addressing of nodes