ccna 1 chapter 9 pdf

ccna 1 chapter 9 pdf.In addition to the way frames are composed like HDLC, PPP defines a set of Layer 2 control protocols that are dedicated to performing various link control functions. The concept of defining these additional protocols is somewhat like the additional STP protocols for Ethernet. The Ethernet header and tail define frames, and it also defines overhead protocols like STP to help make the frame forwarding process smoother. Similar to this, PPP defines the frame format in Figure 12-12, and it also defines other protocols to help manage and control the serial link. PPP divides these control protocols into the following two categories. /Link Control Protocol (LCP):This protocol has several distinct and separate functions, each focused on the data link itself and not affecting the Layer 3 protocols on that link at all.2. .260 Chapter 12 Point-to-Point WAN Network Control Protocol (NCP): this is a class of protocols, one for each network layer protocol. Each protocol acts only on the Layer 3 protocol to which it relates. PPP LinkControlProtocol (LCP) implements the same control functions regardless of the Layer 3 protocol. For features associated with higher-level protocol characteristics, typically Layer 3 protocols, PPP uses a series of PPP ControlProtocols (CP), such as the IP Control Protocol (IPCP) O PPP uses one instance of LCP for each link and applies one NCP for each Layer 3 protocol defined on the link. For example, on a PPP link using IPv4,IPv6, and Cisco Discovery Protocol (CDP), the link uses one instance of LCP, plus IPCP (for IPv4), IPv6CP (for IPv6), and CDPCP (for CDP). Table 12-4 summarizes the LCP features, names the LCP features, briefly explains them, and the following table explains one of the features, PPP authorization, in detail. Table 12-4 PPPLCP FeaturesFunction LCP Feature DescriptionLoop Link Detection Magic Number Disables the interface if a link is detected to form a loop and allows re-routing through the route that is workingError Detection Link Quality Monitoring (LQM) Disables interfaces that exceed the error percentage threshold and allows rerouting through better routesMulti-link support Multi-link PPP load-balances traffic over multiple parallel linksAuthentication PAP and CHAP exchange of user names and passwords allows each device to identify the device on the other end of the linkPPP AuthenticationThe term "Authentication" in networking refers to a set of security features that help a device confirm that another device should be allowed to communicate and is not an impostor.For example, assuming R1 and R2 are communicating over a serial link, Rl may want R2 to somehow confirm that it is the real R2. authentication provides a way to prove its identity.