// SETTINGS frame with the ACK flag set and a length
		// field value other than 0 MUST be treated as a
		// connection error (Section 5.4.1) of type
		// FRAME_SIZE_ERROR.
		countError("frame_settings_ack_with_length")
		return nil, http2ConnectionError(http2ErrCodeFrameSize)
	}
	if fh.StreamID != 0 {
		// SETTINGS frames always apply to a connection,
		// never a single stream. The stream identifier for a