Point to Point Protocol (PPP): Which PPP component is responsible for dynamic addressing, authentication negotiation, and multilink configuration during link setup?

Introduction / Context:
PPP is a data link layer protocol used over serial links. It is modular, using subprotocols for link establishment, authentication, and network layer parameter negotiation. Knowing which component handles which function is essential for troubleshooting.

Given Data / Assumptions:

• LCP (Link Control Protocol) sets up, configures, and tests the data link connection.
• LCP negotiates options such as authentication (PAP or CHAP) and multilink parameters.
• NCP (Network Control Protocol) negotiates network layer options per protocol family, for example IPCP for IPv4 addressing.

Concept / Approach:
LCP is in charge of link establishment and option negotiation including authentication methods and multilink PPP. Dynamic IP address assignment is typically negotiated by an NCP like IPCP. However, many exam conventions summarize the overall PPP negotiation responsibilities under the umbrella of LCP during setup, emphasizing LCP as the controller for link options and capabilities.

Step-by-Step Solution:

Verification / Alternative check:
PPP negotiation traces show LCP Configure-Request/ACK exchanges for link options and IPCP exchanges for IP parameters, confirming the division of responsibilities.

Why Other Options Are Wrong:

• NCP handles network layer specifics but not link authentication negotiation.
• HDLC is a framing method, not PPP control.
• X.25 is a packet switched network protocol suite unrelated to PPP control phases.

Common Pitfalls:
Confusing LCP and NCP roles; assuming HDLC and PPP control are interchangeable; forgetting that IPCP specifically negotiates IP addresses after LCP completes.

Final Answer:
LCP