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Hi,
I am new in network and practicing to use PPP network over VPN. Here I am not able of figure out the number of processes involved in the service. There are other more protocols to work on but I have a ready made network setup. I had made some successful data transfer some sometime the packets gets loose in the middle of network. I had found this via a sniffing tool.
PPP is one of the two protocols from the standardization of communications on serial links (Brief being the second). It not only allows the encapsulation of data-grams, but also the resolution of certain issues related to network protocols such as assignment and management of addresses (IP, X25 and others). There are lots of things you have to work here.
A connection Ppp consists mainly of three parts. The first is a method for encapsulating data-grams over serial link. DPI uses the HDLC frame format (High Level Data Control), ISO (International Organization Standardization). The second is a Link Control Protocol (LCP - Link Control Protocol) to establish, configure and test the data link connection and the third is many network control protocols (NCPs - Network Control Protocol) for establishing and configuring different network layer protocols.
There are various services engaged in a PPP protocol. So working on that you must know about them. The first is Pennant which is as pacer frame equal to the value 01111110. Only one flag is required between two frames. The other one is Address where PPP does not address individual stations, therefore this field must be 0xFF (all stations). Any unrecognized address will destroy the fabric. The comes Control which is the control field shall be 0x03.
Any connection Ppp begins and ends with a phase of dead link. Once an external event indicates that the physical layer is ready, the connection goes to the next phase, namely the establishment of the link. As Ppp must be supported by a large number of environments, a specific protocol has been developed and integrated Ppp any connection phase, it is LCP (Link Control Protocol). Lcp is a protocol used to establish, configure, test, and complete the connection Ppp. It can handle various sizes of packages and performs a number of tests on the configuration. It can detect a particular link looped on itself.
If authentication is successful or it has not been requested, the connection enters phase Network Protocol. It was at this stage that the various network protocols which are configured in the network. This configuration is done separately for each network protocol. It is provided by the Network Control Protocol (NCP) appropriate. At this time, the data transfer is possible.
The principle is to create PPTP packets under the protocol Ppp and encapsulate them in IP datagrams. Pptp tunnel creates a level 3 protocol defined Greece (Generic Routing Encapsulation). The PPTP tunnel is characterized by an initialization of the client, a control connection between the client and the server and the closure of the tunnel by the server.