S4C4 PPP

Protocols Point to Point Protocol Link Control Protocol Network Control Program Password Authentication Protocol Challenge Handshake Authentication Protocol

Protocols Point to Point Protocol Link Control Protocol Network Control Program Password Authentication Protocol Challenge Handshake Authentication Protocol

Internet Connectivity Problems Provides method for encapsulation of datagrams using HDLC Used LCP to establish, configure and test data-link connections Uses a family of Network Control Protocols to establish and configure different network layer protocols Supports IP, IPX, and Appletalk

PPP Layered Architecture Layer 1 –Synchronous/Asynchronous physical media Layer 2 –Authentication and LCP –BCP (bridge control protocol) Layer 3 –Network Control Protocol, IPCP, IPXCP, IP, IPX, IPXCP

PPP Frame Formats Flag Address Control Protocol – identify encapsulated protocol Data FCS

PPP PPP Session Establishment/Termination Establish Link Link Quality Network Layer Protocol Link Termination

Link Establishment and Configuration Negotiation Each PPP device sends IP packets to configiure and establish a link Option field allows devices to negotiate use of options such as maximum transmission unit LCP must open connection and negotiate configuration parameters before datagrams can be exchanged

Link Quality Negotiation Link is tested to determine if link quality is good enough to support network layer protocols Client can be authenticated –PAP –CHAPdetailed in RFC 1334

Network Layer Configuration NCP configures network layer protocols –PPP devices send NCP packets to choose and configure one or more network layer protocols –Then datagrams can be sent over the link –When LCP closes the link, network layer protocol is notified so it can take appropriate action –Check LCP and NCP states using show interfaces

Link Determination Router(config-if)# ppp encapsulation –Activates PPP on interface and link Terminated at request of user or physical event such as loss of carrier or timeout

PAP Performs layer 2 authentications Weak, subject to hacking Takes place before network layer protocol configuration phase begins Simple method for remote node to establish its identify –Uses two-way handshake –Password sent in text

CHAP Preferred over PAP Periodic, unannounced challenges –Does not allow caller to attempt authentication without a challenge –Uses secret known only to authenticator and peer Three-way handshake