Network Control Protocol (NCP) is responsible for negotiating upper-layer protocols that will be carried across the PPP connection. NCP defines how the two PPP peers negotiate with the network layer protocols, such as IP and IPX, which will be used across the PPP connection.

Link Control protocol (LCP) is not responsible for negotiating upper-layer protocols that will be carried across a PPP connection. Link Control protocol (LCP) has the primary responsibility of negotiating and maintaining the PPP connection. LCP, defined in Request for Comments (RFCs) 1548 and 1570, has the primary responsibility to establish, configure, authenticate, and test a PPP connection. LCP negotiates the following when setting up a PPP connection:
* Authentication method used (PAP or CHAP), if any
* Compression algorithm used (Stacker or Predictor), if any
* Callback phone number to use, if defined
* Multilink; other physical connections to use, if configured

Local Management Interface (LMI) is not responsible for negotiating upper-layer protocols that will be carried across the PPP connection. LMI is a characteristic of a frame relay connection. There are three types of LMIs supported by Cisco routers:
* Cisco
* ANSI Annex D
* Q933-A Annex A

LMI has nothing to do with PPP connections.

Integrated Services Digital Network (ISDN) is a type of WAN connection and has nothing to do with PPP connections.