CISCO CCNA 200-301 Q62

Which protocol is responsible for negotiating and maintaining Point-to-Point Protocol (PPP) connections?


Correct Answer: A

Link Control protocol (LCP) has the primary responsibility of negotiating and maintaining a 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

The ability to utilize compression, authentication, and multilink are three options that make PPP a popular choice for Layer 2 encapsulation over a WAN link.

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

In summary, the three steps in the establishment of a PPP session are: Link establishment phase
Optional authentication phase Network layer protocol phase

Basic Rate Interface (BRI) and Integrated Services Digital Network (ISDN) are not components of PPP, so these options are incorrect. BRI is a type of ISDN connection that contains three circuits, two 64K B or bearer channels, and one D or Delta channel. ISDN circuits are a type of WAN connection.