最上面是用户空间层，或称为应用层，其中定义了网络栈的用户。
At the top is the user space layer, or application layer, which defines the users of the network stack.
从一个用户应用层的程序编写者的角度来看，这两者很难区分。
From the perspective of a userspace programmer, it is very difficult to tell the two apart.
系统层包括统一用户管理、统一资源管理和统一作业管理三部分，为应用层提供服务保障。
System layer includes single user management, single resource management and single job management system, and it can offer the service for application layer.
应用推荐