The PPP: Point to Point Protocol

The point-to-point protocol (PPP) for in point-to-point connections on multi-protocol packet transmission provides a standard method. The PPP originally designed for two equivalence between nodes of IP flows transmission provides a encapsulation protocol. The TCP - the IP protocol centralized it is used as a synchronization modulation connecting data link layer protocol (OSI model of the second floor), has replaced the original non-standard layer 2 protocol, namely the SLIP. Besides IP outside the PPP can also carry other agreements, including the Internet DECnet and Novell network packet switching (IPX).

The PPP mainly by the following several parts:

Package: a package multi-protocol data submitted to the method. The PPP encapsulation provide different network layer protocols simultaneously in the same link transmission multiplexing technique. The PPP encapsulation elaborate design, can keep for most common hardware compatibility. To overcome the shortcomings of SLIP a multipurpose, point-to-point protocol, it provides WAN data link encapsulation services similar to the closed service provided by the LAN. So, the PPP not only provides frame bound, and provide agreement logo and a level integrity checking service.

Link control protocol, an extended link control protocol used to establish, configuration, testing and management data link connection.

Network control protocol: negotiation this link in the transmission packet format and types, establish and configuration of different network layer protocols,

Configuration: use the link control protocol of simple and self-control mechanism. This mechanism is also applied to the other control protocol, such as: network control protocol (NCP).

In order to establish a point-to-point link communication, the PPP link of each end, must first send LCP packet to set and test data link. In the link establishment phase, LCP required optional function was selected, the PPP must send after NCP bag to choose and to set up one or more network layer protocols. Once each of the selected network layer protocols were set good, from each of the network layer protocol data submitted to can across the link sent.

Link will remain unchanged, until one communication set NCP packet close links with LCP, or something happened when external events (e.g., heads of state or timer expires network administrator interference).

Should use: suppose is also in Windows 98, and has created good "dial-up connection". So can through the following methods to set the PPP agreement: first, open "dial-up connection" the attribute, likewise choosing "server type" TAB, Then, select the default "PPP: Internet, Windows NT Server, Windows 98," in advanced options can set this agreement other option, Finally, click the "ok" button.

The PPP workflow:

When the user dial-up access ISP, the router to dial-up modem confirms, and build a physical connection (bottom up).

PC to router to send a series of LCP packet (package into multiple PPP frame).

These group and its response to choose some PPP parameters, and the network layer configuration (formerly if any validation should first PAP or outlined through verification), to new access NCP PCS to allocate a temporary IP address, make the PC becomes one of the hosts on the Internet.

Communication finished, NCP release the network layer connection, recover original allocated the IP address. Then, LCP release data link layer connection. The release of is the physical connection.