diff --git a/api/cds.proto b/api/cds.proto
index 86a2906cf..a80137fdf 100644
--- a/api/cds.proto
+++ b/api/cds.proto
@@ -161,24 +161,20 @@ message Cluster {
   //   verification.
   UpstreamTlsContext tls_context = 11;
 
-  oneof protocol_options {
-    // [#not-implemented-hide:]
-    TcpProtocolOptions tcp_protocol_options = 12;
-
-    // Additional options when handling HTTP1 requests.
-    Http1ProtocolOptions http_protocol_options = 13;
-
-    // Even if default HTTP2 protocol options are desired, this field must be
-    // set so that Envoy will assume that the upstream supports HTTP/2 when
-    // making new HTTP connection pool connections. Currently, Envoy only
-    // supports prior knowledge for upstream connections. Even if TLS is used
-    // with ALPN, `http2_protocol_options` must be specified. As an aside this allows HTTP/2
-    // connections to happen over plain text.
-    Http2ProtocolOptions http2_protocol_options = 14;
-
-    // [#not-implemented-hide:]
-    GrpcProtocolOptions grpc_protocol_options = 15;
-  }
+  reserved 12;
+
+  // Additional options when handling HTTP1 requests.
+  Http1ProtocolOptions http_protocol_options = 13;
+
+  // Even if default HTTP2 protocol options are desired, this field must be
+  // set so that Envoy will assume that the upstream supports HTTP/2 when
+  // making new HTTP connection pool connections. Currently, Envoy only
+  // supports prior knowledge for upstream connections. Even if TLS is used
+  // with ALPN, `http2_protocol_options` must be specified. As an aside this allows HTTP/2
+  // connections to happen over plain text.
+  Http2ProtocolOptions http2_protocol_options = 14;
+
+  reserved 15;
 
   // If the DNS refresh rate is specified and the cluster type is either
   // :ref:`STRICT_DNS<envoy_api_enum_value_Cluster.DiscoveryType.STRICT_DNS>`,
@@ -417,6 +413,16 @@ message Cluster {
   // For instance, if the metadata is intended for the Router filter, the filter
   // name should be specified as *envoy.router*.
   Metadata metadata = 25;
+
+  enum ClusterProtocolSelection {
+    // Cluster can only operate on one of the possible upstream protocols (HTTP1.1, HTTP2).
+    // If :ref:`http2_protocol_options <envoy_api_field_Cluster.http2_protocol_options>` are
+    // present, HTTP2 will be used, otherwise HTTP1.1 will be used.
+    USE_CONFIGURED_PROTOCOL = 0;
+    // Use HTTP1.1 or HTTP2, depending on which one is used on the downstream connection.
+    USE_DOWNSTREAM_PROTOCOL = 1;
+  }
+  ClusterProtocolSelection protocol_selection = 26;
 }
 
 // An extensible structure containing the address Envoy should bind to when