Once the three phases of negotiation have been completed, PPP begins to forward data to and from the client and server. Data is sent by PPP when IP passes it a packet to transmit. Each transmitted data packet is wrapped in a PPP header, which is removed by the receiving computer. If data compression was selected in Phase 1 and negotiated in Phase 3, data will be compressed before transmission. If data encryption was similarly selected and negotiated, the data (optionally compressed) will be encrypted before transmission. PPP then passes the packet to the miniport driver — for example, AsyncMac — which performs appropriate framing and transmits it to the physical layer. Packet reception is done using these same steps in reverse order.
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