XGS-5240-Series User Manual

Configuration Guide of XGS-5240-Series
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sent to many access collector of the network.
2. Broadband Access Server responds PADO packet: The second step, server re
sponds PADO (PPPoE Active Discovery Offer) packet to client according to th
e received source MAC address of PADI packet, the packet will take sever na
me and service name.
3. Client sends PADR packet: The third step, client selects a server to process t
he session according to the received PADO packet. It may receives many PA
DO 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 packe
t match with the servce information needed by client). MAC address of the oth
er end used for session will be known after server is selected, and send PAD
R (PPPoE Active Discovery Request) packet to it to announce server the sess
ion requirement.
4. Server responds PADS packet: The fourth step, server establishes a session I
D according to the received PADR packet, this session ID will be sent to clien
t 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 b
e considered a packet of discovery stage. To stop a PPPoE session, PADT may be se
nt 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. Wh
en 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 l
ocate 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 Migr
ation to Ethernet-based DSL aggregation.
1.1.1.25 PPPoE Intermediate Agent Exchange Process
PPPoE Intermediate Agent exchange process is similar to PPPoE exchange proces
s, for the first exchange process, the access link tag is added to PADI and PADR pac
kets. The exchange process is as follows: