diff --git a/agent/pool/conn.go b/agent/pool/conn.go
index 8c81d25327..07e8f41721 100644
--- a/agent/pool/conn.go
+++ b/agent/pool/conn.go
@@ -17,4 +17,14 @@ const (
 	// that is supported and it might be the only one there
 	// ever is.
 	RPCTLSInsecure = 7
+
+	// NOTE: Currently we use values between 0 and 7 for the different
+	// "protocols" that we may ride over our "rpc" port. We had an idea of
+	// using TLS + ALPN for negotiating the protocol instead of our own
+	// bytes as it could provide other benefits. Currently our 0-7 values
+	// are mutually exclusive with any valid first byte of a TLS header
+	// The first TLS header byte will content a TLS content type and the
+	// values 0-19 are all explicitly unassigned and marked as
+	// requiring coordination. RFC 7983 does the marking and goes into
+	// some details about multiplexing connections and identifying TLS.
 )