Notes on Point to Point WANs

PPP Link Control ( LCP ) Features

  • Looped link detection - magic number - detects if a link is looped and sibles that interface
  • error detection - link quality monitoring - disables an interface that exceeds an error threshold
  • multilink support - multilink PPP - load balances traffic over multiple parallel links
  • authentication - pap, chap - exchanges names and passwords to authenticate devices.
Looped Link Detection - LCP uses a magic number sent in the LCP message. If the router receives a message with it's own magic number, it knows it is a looped interface and brings down the interface. If the interface was not looped it would of received the magic number of the other router.

Enhanced Error Detection - analyzes the number of errors received on an interface and if it breaches a certain threshold will take the interface down to prevent network congestion.

PPP Multilink - Is a load balancing method used in PPP. When more than one connection exists between to routers, it allows a layer 3 protocol to see the links as one. However it will force equal load balancing of packets between the links. Even though the layer 3 protocol sees one route.

PPP Authentication - refers to a set of security functions that help one device confirm the that the other device is authorized to communicate. PAP and CHAP are PPP authentication methods.