计算机网络体系结构 oS参考模型 exchanged 应用层 7 Application Application protocol Applicati APDU Intertace 表示层 6 Presentation Presentation protocol Presentatio 会话层5 session P Session SPDU 传输层4「 Transport Transport protocol Transport Communication subnet boundary Intemal subnet protocol 网络层3 Network Network Network Network Pecket 数据连路层 2 Data link H Date link nk Dete ln Date lin. Freme 物理层「Pyh Physical Physical Physica Host A Router Router Host B Network layer host-router protocol Data link layer host router protocol Physical layer host-router protocolOSI参考模型 物理层 数据连路层 网络层 传输层 会话层 表示层 应用层 计算机网络体系结构