20040426 Class notes:
1. Exams Chap1, 2 and CCNA are available 
   till midnight
2. int s0/0
      encaplation hdlc
   or encapsulation ppp
3. Time-Division Multiplexing (TDM) 
4. Link Access Protocols:
   LAPB	for X.25
   LAPD	for ISDN
   LAPM or PPP for modem
   LAPF for Frame-Relay
5. sh int interpretation: 3.1.7 figure 3
6. PPP: LCP + NCP
7. PPP frames:
   	Link establishment
   	Link termination
	Link maintenance
8. PPP phases:
	Link establishment
	Authentication
	Network layer protocol
9. PPP authentication: PAP or CHAP