PPP API - PowerPoint PPT Presentation

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PPP API

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  1. PPP API 1-1

  2. PPP Overview Three types of Protocols • Link Connect Protocols • Authentication Protocols • Network Protocols 1-2

  3. Link Protocols • To be portable to a wide variety of environments, PPP provides a Link Control Protocol (LCP). • The LCP is used to • automatically agree upon the encapsulation format options, • handle varying limits on sizes of packets, • detect a looped-back link and other common misconfiguration errors, and • terminate the link. 1-3

  4. Link Phase Diagram Dead Establish Authenticate Up Opened Success/None Fail Fail Terminate Network Down Closing 1-4

  5. Authentication Protocols • CHAP - Challenge Handshake Authentication Protocol • Used to periodically verify the identity of the peer using a 3-way handshake • Done upon initial link establishment, and MAY be repeated anytime afterward • Process: • After the Link Establishment phase is complete, the authenticator sends a "challenge" message to the peer. • The peer responds with a value calculated using a "one-way hash" function. • The authenticator checks the response against its own calculation of the expected hash value. If the values match, the authentication is acknowledged; otherwise the connection SHOULD be terminated. • At random intervals, the authenticator sends a new challenge to the peer, and repeats steps 1 to 3. • PAP - Password Authentication Protocol • Allows for a username and password to be included • Device attached to has to check and ok password 1-5

  6. Network Control Protocols • Can handle more than one network type • First configure the network type • Include information about network in each communication 1-6

  7. Types of PPP Control • Two Types of control • Serial Link Control • Modem Link Control 1-7

  8. Material Needed for PPP Examples • A PPP Host that can be accessed over a serial port • Two Modems • A remote access server 1-8

  9. Supported Functions • Can handle PPP over direct serial • Can handle modem setup and PPP • Requires fixed IP addresses 1-9

  10. Example Applications • Echo Client to Remote Echo Server through Remote Access Server over Modem on Com2 • FTP Server Available through Direct Serial Connection on Com1 • HTTP Server Available through Remote Access Over Modem on COM2 • IP Routing Between a Direct Serial Connection to a Modem Connection 1-10

  11. Echo Client to Remote Echo Server through Remote Access Server over Modem on Com2 • Modem connection with modem control • Sets modem to either send or receive • Sends and receives data • Have to adjust numbers and IP addresses 1-11

  12. FTP Server Available through Direct Serial Connection on Com1 • Serial connection only • Has authentication built in • IP addresses need to be set 1-12

  13. HTTP Server Available through Remote Access Over Modem on COM2 • Uses modem connection • Sets up modem configuration and makes or allows calls • Waits for call • Acts as webserver 1-13

  14. IP Routing Between a Direct Serial Connection to a Modem Connection • Combination version • Uses serial for one connection • Modem for other connection • Sends data to modem to setup for operation • Board waits for connection on modem • Already has connection over serial 1-14

  15. State Diagrams 1-15

  16. Modem State Diagram NASetSysAccess Unitialized PPPCreateDevice PPPSetModemAutoAnswerRingsPPPSetModemDialString PPPSetVJ PPPSetPeerAddr PPPSetAuth Stopped PPPModemClose PPPModemInit Started PPPCheckLink PPPAddRoute PPPDelRoute PPPGetPeerAssignedAddress 1-16

  17. Direct Serial State Diagram NASetSysAccess Unitialized PPPCreateDevice Stopped PPPSetVJ PPPSetPeerAddr PPPSetAuth PPPSerialClose PPPSerialInit Started PPPCheckLink PPPAddRoute PPPDelRoute PPPGetPeerAssignedAddress 1-17

  18. State Diagrams 1-18

  19. PPP Enhancements - API Changes • PPPAddUser() superseded by NAsetSysAccess() • PPPSetAuthentication() superseded by PPPSetAuth() • PPPDelRoute() was added for cases where addresses provided by remote site such as an ISP • PPPGetPeerAssignedAddress() was added to get address from a remote site such as an ISP 1-19

  20. PPP Enhancements - Modem Driver Changes • AT&FE1 modem command from NET+OS 3 removed • Modem hardware hang up / reset (toggle DTR) replaces software hang up / reset (+++ATH command) • Dial-up client mode no longer sends ATS0=x command, only dial-up server mode sends ATS0=x command 1-20

  21. PPP Enhancements - Application Changes • NAsetSysAccess() replaces PPPAddUser() in all examples • PPPSetAuth() replaces PPPSetAuthentication() in all examples • Dial-up client example (echomod2) modified to better handle common modem communications errors. The code outlines how to close the modem on a disconnect so that the connection can be reestablished. 1-21