Which layer of the OSI model provides network services to processes in electronic mail and file transfer programs?

在OSI模型的那一层提供网路服务去处理电子邮件何档案传输程式?。

youdao

Which layer of the OSI model provides network services to processes in electronic mail and file transfer programs?

在OSI模型的那一层提供网路服务去处理电子邮件何档案传输程式?。

youdao