Packet Types

Table 1-1 “Packet Types” lists the packets exchanged between the host and the access concentrator during the discovery stage.

Table 1-1 Packet Types

Packet	Description
`PADI`	The host sends the PPPoE Active Discovery Initiation (`PADI)` packet with the destination address set to the broadcast address.
`PADO`	When an access concentrator receives a `PADI` that it can serve, it responds to the host by sending a PPPoE Active Discover Offer (`PADO)` packet. The destination address is the unicast address of the host that sent the `PADI`.
`PADR`	Since the `PADI` was broadcast, the host may receive more than one `PADO`. The host examines the `PADO` packets it receives and selects one. The host then sends one PPPoE Active Discovery Request (`PADR)` packet to the access concentrator that it has selected. The destination address field is set to the unicast Ethernet address of the access concentrator that sent the `PADO`.
`PADS`	When the access concentrator receives the `PADR` packet, it prepares to start a PPP session. It generates a unique `session ID` for the PPPoE session and responds to the host with a PPPoE Active Discovery Session-confirmation (`PADS)` packet. The destination address field is the unicast Ethernet address of the host that sent the `PADR`.
`PADT`	Either the client or the server sends a PPPoE Active Discovery Terminate (`PADT`) packet to terminate a PPP session. The destination address field is a unicast Ethernet address. When a `PADT` is received, no further PPP traffic is sent through that session.

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