Editing Point-to-Point Protocol (section)

===Automatic self configuration===

LCP initiates and terminates connections gracefully, allowing hosts to negotiate connection options. It is an integral part of PPP, and is defined in the same standard specification. LCP provides automatic configuration of the interfaces at each end (such as setting [[datagram]] size, escaped characters, and magic numbers) and for selecting optional authentication. The LCP protocol runs on top of PPP (with PPP protocol number 0xC021) and therefore a basic PPP connection has to be established before LCP is able to configure it.

RFC 1994 describes [[Challenge-Handshake Authentication Protocol]] (CHAP), which is preferred for establishing dial-up connections with ISPs.
Although deprecated, [[Password Authentication Protocol]] (PAP) is still sometimes used.

Another option for authentication over PPP is [[Extensible Authentication Protocol]] (EAP) described in RFC 2284.

After the link has been established, additional network ([[Network layer|layer 3]]) configuration may take place. Most commonly, the [[Internet Protocol Control Protocol]] (IPCP) is used, although [[IPX/SPX|Internetwork Packet Exchange Control Protocol]] (IPXCP) and [[AppleTalk|AppleTalk Control Protocol]] (ATCP) were once popular.<ref>{{Cite report |url=https://datatracker.ietf.org/doc/rfc1552/ |title=The PPP Internetworking Packet Exchange Control Protocol (IPXCP) |last=Simpson |first=William A. |date=December 1993 |publisher=Internet Engineering Task Force |issue=RFC 1552}}</ref><ref>{{Cite report |url=https://datatracker.ietf.org/doc/rfc1378/ |title=The PPP AppleTalk Control Protocol (ATCP) |last=Parker |first=J. Bradford |date=November 1992 |publisher=Internet Engineering Task Force |issue=RFC 1378}}</ref> [[IPv6CP|Internet Protocol Version 6 Control Protocol]] (IPv6CP) will see extended use in the future, when [[IPv6]] replaces [[IPv4]] as the dominant layer-3 protocol.