Configuration Guide Configuring PPPoE Client
6.3.1.2 Overview
In a scenario where Internet access is implemented through the Asymmetric Digital Subscriber Line
(ADSL) technology, the device provides dialup and packet forwarding functions.
6.3.2 Dialup to the Internet
The device has Internet access capability after the dialup is complete; therefore, hosts in the intranet also have Internet
access capability.
6.3.2.1 Working Principle
Dialup corresponds to the negotiation process, whereas Internet access corresponds to the packet forwarding process.
Negotiation can be further divided into three parts: protocol negotiation, protocol keepalive, and protocol termination.
Protocol Negotiation
Protocol negotiation is divided into PPPoE negotiation and PPP negotiation.
During PPPoE negotiation, both parties confirm a unique peer, record the peer's MAC address, and establish a unique
session ID.
During PPP negotiation, the server checks the client's authentication information. If the client passes the authentication, the
server allocates an IP address to the client. If the client has already been configured with an IP address and the configured IP
address meets the server's requirements, the server will agree to use this IP address as the IP address of the client.
After both protocols are up, the device has Internet access capability and prepares a Layer 2 (L2) header that is necessary
for data packet encapsulation.
Protocol Keepalive
After PPP is up, both parties periodically send LCP heartbeat packets to each other. If the party at one end does not receive
any heartbeat response from the other party, it actively terminates the protocol.
Protocol Termination
In certain cases, either party may actively terminate the protocol.
The initiating party sends a PPP termination packet to end the current PPP session, and then sends a PPPoE termination
packet to end the current PPPoE session.
After receiving the PPP termination packet, the passive party returns an acknowledgement packet to agree to the termination
of the PPP session; and after receiving the PPPoE termination packet, the passive party returns another acknowledgement
packet to agree to the termination of the PPPoE session.
Once either party receives a PPPoE termination protocol, the PPP session and the PPPoE session will immediately
terminate, even if it has not received any PPP termination protocol.
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