QTECH QSW-3400 Инструкция по настройке - Manual (Page 375)

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3. Client sends PADR packet: The third step, client selects a server to process the session
according to the received PADO packet. It may receives many PADO packets for PADI
message of the first step may be sent to many servers (select the server according to
whether the service information of PADO packet match with the servce information needed
by client). MAC address of the other end used for session will be known after server is
selected, and send PADR (PPPoE Active Discovery Request) packet to it to announce
server the session requirement.
4. Server responds PADS packet: The fourth step, server establishes a session ID according
to the received PADR packet, this session ID will be sent to client through PADS (PPPoE
Active Discovery Session-confirmation) packet, hereto PPPoE discovery stage is
completed, enter session stage.
PADT (PPPoE Active Discovery Terminate) packet is an especial packet of PPPoE, its’
Ethernet protocol number (0x8863) is the same as four packets above, so it can be considered
a packet of discovery stage. To stop a PPPoE session, PADT may be sent at the discretional
time of the session. (It can be sent by client or server)
PPPoE Intermediate Agent supplies a function that identify and locate the user. When passing
network access device, PADI and PADR messages sent by client with the access link tag of
this device at PPPoE discovery stage, so as to exactly identify and locate the user on server.
If the direct-link access device is LAN switch, the added information include: MAC, Slot ID,
Port Index, Vlan ID, and so on. This function is implemented according to Migration to
Ethernet-based DSL aggregation.
49.1.2.1 PPPoE Intermediate Agent Exchange Process
PPPoE Intermediate Agent exchange process is similar to PPPoE exchange process, for the
first exchange process, the access link tag is added to PADI and PADR packets. The
exchange process is as follows: