Point to Point Protocol (PPP): Which PPP component is used to identify and negotiate the Network layer protocol parameters on the link?

Introduction / Context:
PPP separates link control from network layer parameter negotiation using distinct control protocols. After the link is established by LCP, the appropriate Network Control Protocol (NCP) runs to configure per protocol options such as IP addressing.

Given Data / Assumptions:

• LCP handles link establishment, authentication negotiation, and option exchange.
• NCP family members include IPCP for IPv4 and IPV6CP for IPv6.
• The question asks specifically about identifying and negotiating Network layer protocols.

Concept / Approach:
NCP determines which Network layer protocols will be carried over the PPP link and negotiates their parameters. For example, IPCP can request IP address assignment dynamically, DNS options, and compression settings. Only after successful NCP negotiation is the network layer ready to pass traffic.

Step-by-Step Solution:

Verification / Alternative check:
PPP debug traces show LCP Configure messages followed by IPCP or IPV6CP Configure messages, confirming the division of labor.

Why Other Options Are Wrong:

• ISDN is a physical access technology, not a PPP control protocol.
• HDLC provides framing but not parameter negotiation at the network layer.
• LCP handles link control, not network layer option negotiation.

Common Pitfalls:
Mixing up LCP and NCP roles; assuming address assignment happens during LCP; overlooking that multiple NCPs can run concurrently if multiple network protocols are used.

Final Answer:
NCP