expedited(N)-service-data-unit

A small (N)-service-data-unit whose transfer is expedited. The (N)-layer ensures that an expedited-data-unit will not be delivered after any subsequent service- data-unit or expedited unit sent on that connection.; 一种需要加速传送的数据量较少的某一层的服务数据单元,该层应确保某一加速数据单元 在此连接上随后出现的任何服务数据单元或加速数据单元之前交付。