In sna , the layer within a half session that routes fmd requests and responses to particular nau services manager components and that provides session network services or session presentation services , depending on the type of session 在系統(tǒng)網(wǎng)絡(luò)體系結(jié)構(gòu)( sna )中,部分話路內(nèi)的服務(wù)層,負(fù)責(zé)把操作管理數(shù)據(jù)( fmd )請(qǐng)求和響應(yīng)郵送給特定網(wǎng)絡(luò)可尋址單元( nau )服務(wù)管理程序,并提供話路網(wǎng)絡(luò)服務(wù)或話路表示服務(wù),具體是哪種服務(wù)依話路類型而定。