Which PPP sub-protocol negotiates authentication options?
A. NCP
B. ISDN
C. SLIP
D. LCP
E. DLCI
Answer: D
Explanation:
PPP defines the Link Control Protocol (LCP). The job of the LCP is to establish, configure, and test the data-link connection. When hosts negotiate a PPP connection, they exchange LCP packets. These packets allow link partners to dynamically negotiate link options, including authentication, compression, and MLP. The protocol field is used to
identify various Layer 3 protocols, such as IP or IPX. The LCP field allows for the following features:
1. Authentication
2. Callback
3. Compression
4. Multilink PPP
Once the LCP establishes the Layer 2 connection, the Network Control Protocol (NCP) takes over. Link partners exchange NCP packets to establish and configure different network-layer protocols including IP, IPX, and AppleTalk. Each Layer 3 protocol has its own NCP. For example, IP’s NCP is IPCP. IPX’s NCP is IPXCP and Appletalk’s NCP is
ATALKCP.