|  | 4.2 | PPP Session Establishment
| 4.2.2 | Phase 1: link establishment and configuration negotiation
In the link establishment and configuration negotiation phase, each PPP device sends LCP packets to configure and establish the data link. LCP packets contain a configuration option field that allows devices to negotiate the use of options, such as the maximum transmission unit (MTU), compression of certain PPP fields, and the link authentication protocol. If a configuration option is not included in an LCP packet, the default value for that configuration option is assumed. Before any network-layer datagrams (for example, IP) can be exchanged, LCP must first open the connection and negotiate the configuration parameters. This phase is complete when a configuration acknowledgment frame has been sent and received.