nUser services
 and terminals (as IN services: call last dialed...)
 nStandards (IETF, IEEE, ITU-T ...)
 nRouting and switching (unicast - multicast, devices)
 nTransmission and links (as fibre, coax-cable.., RSVP)
 nAccess and transport (terminals, local-loop techniques..)
 nServers service (web,mail,ftp ...)
 nSignaling (SS7, X.25,
 Frame relay ...)
 nNetwork management (as OMAP of SS7...)
 nInterworking between networks (gateways, bridges ...)
 nNetwork planning
 n
  
 
 IN: Intelligent
 Network
 IETF: Internet Engineering
 Task Force
 IEEE: the Institute of
 Electrical and Electronics Engineers, Inc
 RSVP: Resource ReSerVation
 Protocol
 ITU: International
 Telecommunications Union
 SS7: Signaling System
 7
 OMAP: Operation and
 Maintenance Application Part