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HDLC & PPP

HDLC & PPP. Ch 11- 12. Chapter 11.5. High-level Data Link Control HDLC. HDLC supports communication over point-to-point and multipoint links. I-Frame (Information frame): Used to transport user data and control information

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HDLC & PPP

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  1. HDLC & PPP Ch 11- 12

  2. Chapter 11.5 High-level Data Link Control HDLC

  3. HDLC supports communication over point-to-point and multipoint links. I-Frame (Information frame): Used to transport user data and control information S-frame (Supervisory frame): Used only to transport control information. U-frame (Unnumbered frame): Reserved for system management. 11.17HDLC frame

  4. I-Frame has sequence and ACK numbers S-frame contains the code for Receive Ready, Receive Not Ready, Reject, Selective Reject. U-frame is used for session management and control information 11.18HDLC frame types

  5. 11.22Piggybacking without Error

  6. 11.23Piggybacking with Error

  7. Chapter 12 Point-to-PointAccess: PPP

  8. Two devices can be connected by a dedicated link or a shared link.  point-to-point access. Connection to ISP via PPP Format of the frame Negotiate the establishment of the link and the exchange of data How network layer data are encapsulated in the data link frame How two devices can authenticate each other. Flag = 01111110 Address = Broadcast Control field = No sequence numbers and so no flow or error control 12.1PPP frame

  9. Establishing: Negotiation of options 12.2Transition states

  10. Link Control Protocol Negotiation mechanisms. Establishing or terminating state Authentication Protocols Password Authentication Protocol (PAP) Challenge Handshake Authentication Protocol (CHAP) Network Control Protocol 12.3Protocol stack

  11. Send user name and password Check validity and accept or deny. 12.5PAP

  12. 12.6PAP packets

  13. System sends a challenge packet containing challenge value, usually a few bytes User applies predefined function with challenge value, user’s password. The result is sent as response. System does the same as user and compares the result. 12.7CHAP

  14. 12.8CHAP packets

  15. Network Control Protocol is a set of control protocols to allow the encapsulation of data coming from network layer protocols into the PPP frame. The set of packets that establish and terminate a network layer connection for IP packets is called Internetwork Protocol Control Protocol (IPCP). Use configure-request to negotiate with the other party. Ex., to set the IP addresses and so on. 12.9IPCP packet encapsulated in PPP frame

  16. Table 12.3 Code value for IPCP packets

  17. 12.10An example

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