Figure 3: PPP LCP negotiation

+----------------+                                   +-------------------+
|                |Configure-Request----------------->|                   |
|                |                                   |                   |
|                |<-----------------Configure-Request|                   |
|                |                                   |                   |
|                |<----------------------------------|                   |
|      PPP       | Configure-Rejects or NAKs sent    |       PPP         |
|     Client     | until acceptable configurations   |      Server       |
|                | are received.                     |                   |
|                |---------------------------------->|                   |
|                |                                   |                   |
|                |Configure-ACK--------------------->|                   |
|                |                                   |                   |
|                |<-------------------- Configure-ACK|                   |
+----------------+                                   +-------------------+
When each side has both sent and
received a Configure-ACK, the LCP
state is considered "open" and
negotiation turns to Authentication
if some kind of authentication has
been negotiated during LCP.