我使用Spring 5 Webclient和Reactor netty来发出HTTP API POST请求，代码如下所示：

HttpClient httpClient = HttpClient.create()
                .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 5000)
                .option(ChannelOption.SO_KEEPALIVE, true)
                .option(EpollChannelOption.TCP_KEEPIDLE, 300)
                .option(EpollChannelOption.TCP_KEEPINTVL, 60)
                .option(EpollChannelOption.TCP_KEEPCNT, 8)
                .doOnConnected(
                        connection ->
                                connection
                                        .addHandler(
                                                new ReadTimeoutHandler(1000,
                                                        TimeUnit.SECONDS))
                                        .addHandler(
                                                new WriteTimeoutHandler(1000)));

WebClient.builder()
                .baseUrl("//some url")
                .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
                .defaultHeader(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE)
                .clientConnector(new ReactorClientHttpConnector(httpClient))
                .build();

我试图设置TCP配置，如TCP_KEEPIDLE, TCP_KEEPINTERVAL等，因此在项目React器文档中阅读到了相同的内容。
文件说（我在总结）：

//The options below are available only when NIO transport (Java 11) is used
    .option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPIDLE), 300)
    .option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPINTERVAL), 60)
    .option(NioChannelOption.of(ExtendedSocketOptions.TCP_KEEPCOUNT), 8);

//The options below are available only when Epoll transport is used
    .option(EpollChannelOption.TCP_KEEPIDLE, 300)        
    .option(EpollChannelOption.TCP_KEEPINTVL, 60)        
    .option(EpollChannelOption.TCP_KEEPCNT, 8);

我不明白NIO和Epoll****transport之间的区别，或者更具体地说，transport到底是什么？我知道OSI堆栈的传输层和其他层，但不明白这里使用的传输层是什么。如果能解释一下，我将不胜感激。