Network Working Group D. Perkins Request for Comments: 1134 CMU November 1989 The Point-to-Point Protocol: A Proposal for Multi-Protocol Transmission of Datagrams Over Point-to-Point Links Table of Contents Status of this Memo ................................... 2 Abstract .............................................. 2 1. Introduction ....................................... 2 1.1 Motivation ........................................ 2 1.2 Overview of PPP ................................... 3 1.3 Organization of the document ...................... 4 2. Physical Layer Requirements ........................ 4 3. The Data Link Layer ................................ 4 3.1 Frame Format ...................................... 5 4. The PPP Link Control Protocol (LCP) ................ 8 4.1 The LCP Automaton ................................. 9 4.1.1 Overview ........................................ 9 4.1.2 State Diagram ................................... 10 4.1.3 State Transition Table .......................... 12 4.1.4 Events .......................................... 12 4.1.5 Actions ......................................... 14 4.1.6 States .......................................... 16 4.2 Loop Avoidance .................................... 19 4.3 Packet Format ..................................... 19 4.3.1 Configure-Request ............................... 21 4.3.2 Configure-Ack ................................... 21 4.3.3 Configure-Nak ................................... 22 4.3.4 Configure-Reject ................................ 24 4.3.5 Terminate-Request and Terminate-Ack ............. 25 4.3.6 Code-Reject ..................................... 26 4.3.7 Protocol-Reject ................................. 27 4.3.8 Echo-Request and Echo-Reply ..................... 28 4.3.9 Discard-Request ................................. 29 4.4 Configuration Options ............................. 30 4.4.1 Format .......................................... 31 5. A PPP Network Control Protocol (NCP) for IP ........ 32 5.1 Sending IP Datagrams .............................. 33 APPENDICES ............................................ 33 A. Asynchronous HDLC .................................. 33 B. Fast Frame Check Sequence (FCS) Implementation ..... 35 B.1 FCS Computation Method ............................ 35 B.2 Fast FCS table generator .......................... 36 Perkins