介绍了ppp协议的主要内容用户接入Internet，在传送数据时都需要有数据链路层协议，其中最为广泛的是串行 线路网际协议（SLIP）和点对点协议（PPP）。由于SLIP具有仅支持IP等缺点，主要用于低速（不超过19.2kbit/s）的交互性业务，它并未成为Internet的标准协议。为了改进SLIP，人们制订了点对点PPP（Point-to-Point Protocol）。RFC1661、RFC1662、RFC1663。-Ppp protocol introduced the main contents of the user access to Internet, in the transmission of data, we need to have a data link layer protocol, which is the most widely Serial Line Internet Protocol (SLIP) and Point to Point Protocol (PPP). Because SLIP only supports IP, such as with the shortcomings, mainly for low-speed (no more than 19.2kbit/s) of the interactive business, it did not become the Internet standard protocol. In order to improve the SLIP, people developed a point-to-point PPP (Point-to-Point Protocol). RFC1661, RFC1662, RFC1663.