Lcp packets in ppp frame
LCP PACKETS IN PPP FRAME PASSWORD
In case of authentication request from the server, a packet corresponding to an authentication protocol can be sent (PAP, Password Authentication Protocol, or CHAP, Challenge Handshake Authentication Protocol or Kerberos).The padding data is used to adjust the frame length for some protocols.Ī PPP session (from opening to closing) proceeds as follows: Thus, a field in the frame is reserved for the type of protocol to which the packet belongs. These packets are usually datagrams, but they may be something else (hence the specific name of packet instead of datagram). The data encapsulated in a PPP frame are called packets. a set of network control protocols (NCP), allowing controls on the integration of PPP within higher layer protocols.a link control protocol (LCP), allowing test and configuration controls of the communication.PPP is actually a set of three protocols: It is a much more elaborate protocol than SLIP (which is why it has replaced it), as it transfers additional data, which is better suited for data transmission over the Internet (the additional information in a frame is largely due to the increased bandwidth). PPP: the most used protocol for Internet access by modem, it allows addressing machines.SLIP: an older protocol, weak in controls.In this way, there are now two major modem protocols:
The first of them allowed simple data transmission between two machines, then some were equipped with error control, and with the rise of the Internet, they were equipped with the ability to address machines. Thus, many modem protocols were developed. We say that we have a point-to-point connection, that is to say, a connection between two machines limited to its simplest expression: there is no need to share the line between several machines, each one speaks and answers in its turn. These protocols are called modem protocols.ĭefinition of a point-to-point connectionīy the classic telephone line, two computers maximum can communicate by modem together, in the same way as it is not possible to call simultaneously two people by the same telephone line. Since only two computers communicate and the speed of a telephone line is low compared to that of a local network, it is necessary to use a protocol that allows standard communication between the different machines using a modem, and that does not overload the telephone line. The connection is made through a modem, a device capable of converting digital data from the computer into analog signals (which can travel over the telephone line by amplitude or frequency modulation, just like voice when you use the telephone). Most people, not having a line (cable or ethernet) directly connected to the Internet, and are forced to use telephone lines (the most widespread network) to connect to the Internet. The IPCP packets look totally different! They still begin and end with 0x7E and have the HDLC checksum, but there is no address or control bytes, and there's no byte-stuffing.In this tutorial, we are going to see What is PPP in Networking?. They start with 0x7E, the address follows with 0xFF, when the control byte 0x7D23 = 3 followed by byte-stuffed payload, checksum, and the frame character 0x7E. The endpoints exchange LCP packets with configuration requests and then acks, and then one of them begins with an IPCP configuration request shortly afterwards one of them gives up. I'm having trouble with the initial configuration phase.
I'm working on some middleware between a modem and a network stack doing PPP.