This is a beta course, so its structure, chapters, and examples may continue to change.应用层基础概念 This article is being translated. Please check back soon. Previous应用层掌握应用层的网络应用模型、DNS、FTP、电子邮件、WWW和HTTP协议。NextDNS和FTP协议学习DNS域名系统和FTP文件传输协议
