Cayman Systems 2E-H-W User Manual page 152

How Your Cayman 2E-H-W Works
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does not receive a response within the timeout period, it
resends its PADI packet and doubles its timeout period.
2. Offer – If an Access Concentrator for the network can serve the
request, it sends a PPPoE Active Discovery Offer (PADO) packet
to the host identifying its name and the services it can offer to
the host. If more than one Access Concentrator is available, a
host may receive multiple PADO packets.
3. Request – The initiating host chooses an Access Concentrator
(based on its name or the services it offered in its PADO packet)
and sends a PPPoE Active Discovery Request (PADR) message
identifying the service it wants.
4. Confirmation – After the Access Concentrator receives the
PADR message, it generates a unique identifier for the PPPoE
session and replies to the host with a PPPoE Active Discovery
Session-confirmation (PADS) message. The PADS message
identifies the service under which the Access Concentrator has
accepted the PPPoE session.
When the host receives the Confirmation packet from the Access
Concentrator, negotiations are concluded and they can proceed to
the PPP Session stage.
PPP Session Stage
Once the PPPoE session is operative, the host and Access
Concentrator exchange PPP packets using the unique session
identifier they negotiated during discovery.
An Access Concentrator may periodically send ICMP Echo-Request
packets to the host to verify connectivity. This serves to identify
situations where a host terminates a session without sending a
Terminate-Request packet (described in the next section), since the
Access Concentrator might not otherwise be able to determine that
the session is no longer functional.
At any time after they have established a PPP session, either the host
or the Access Concentrator can terminate the session by sending the
other a PPPoE Active Discovery Terminate (PADT) packet. When this
Cayman 2E-H-W User's Guide
November 2000