> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/4.3-bsd-unix-cao-zuo-xi-tong-she-ji-yu-shi-xian/di-yi-bu-fen-gai-lan/2.11.-wang-luo-tong-xin.md).

# 2.11 网络通信

套接字 IPC 机制支持的一些通信域提供对网络协议的访问。这些协议实现为内核中逻辑上位于套接字软件之下的一个独立软件层。内核为各种网络协议提供许多辅助服务：缓冲管理、消息路由、到协议的标准化接口，以及到网络接口驱动的接口。这些服务和接口在第 11 章描述。

4.2BSD 实现之时，使用中和开发中的网络协议众多，各有短长，并没有明显占优的协议或协议套件。通过支持多种协议，4.2BSD 得以在伯克利环境中形形色色的机器之间提供互操作和资源共享。多协议支持也为将来的变化留出了余地：今天为 10 Mbit/s 以太网设计的协议，多半满足不了明天 100 Mbit/s 光纤网络的需要。因此，网络通信层设计成支持多种协议。新协议加入内核，不影响对旧协议的支持；旧应用程序可以继续用旧协议运行，与使用新网络协议的新应用程序共用同一物理网络。


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