3.6. Network-Layer Protocol Phase

Once PPP has finished the previous phases, each network-layer protocol (such as IP, IPX, or AppleTalk) MUST be separately configured by the appropriate Network Control Protocol (NCP).

Each NCP MAY be Opened and Closed at any time.

Implementation Note:

Because an implementation may initially use a significant amount of time for link quality determination, implementations SHOULD avoid fixed timeouts when waiting for their peers to configure a NCP.

After a NCP has reached the Opened state, PPP will carry the corresponding network-layer protocol packets. Any supported network-layer protocol packets received when the corresponding NCP is not in the Opened state MUST be silently discarded.

Implementation Note:

While LCP is in the Opened state, any protocol packet which is unsupported by the implementation MUST be returned in a Protocol- Reject (described later). Only protocols which are supported are silently discarded.

During this phase, link traffic consists of any possible combination of LCP, NCP, and network-layer protocol packets.