* @param protocol an ALPN protocol, such as `h2`.
     * @param host an IP address or hostname.
     * @param port the IP port associated with the service.
     * @param maxAge time in seconds that this alternative is considered fresh.
     */
    fun alternateService(
      streamId: Int,
      origin: String,
      protocol: ByteString,
      host: String,
      port: Int,
      maxAge: Long,
    )
  }