UTT Technologies Chapter 8 User
Management
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Page 138
8.3.1 PPPoE Overview
The PPPoE stands for Point-to-Point Protocol over Ethernet, which uses client/server
model. The PPPoE provides the ability to connect the Ethernet hosts to a Remote
Management Concentrator (AC) over a simple bridging access device. And it provides
extensive access control management and accounting benefits to ISPs and network
administrators.
The PPPoE is a network protocol for encapsulating PPP frames in Ethernet frames to
provide point-to-point connection over an Ethernet network.
8.3.1.1 PPPoE Stages
As specified in RFC 2516, the PPPoE has two distinct stages: a discovery stage and a
PPP session stage. The following describes them respectively.
8.3.1.2 PPPoE Discovery Stage
In the PPPoE discovery stage, a PPPoE client will find a proper server, and then build the
connection. When a client initiates a PPPoE session, it should perform discovery to
indentify the PPPoE server’s Ethernet MAC address, and establish a PPPoE session ID.
Figure 8-12 PPPoE Discovery Stage Flows
As shown in Figure 7-21, the discovery stage includes the following four steps:
1.
PADI (PPPoE Active Discovery Initiation):
At the beginning, a PPPoE client
broadcasts a PADI packet to find all the servers that can be connected possibly. Until
it receives PADO packets from one or more servers. The PADI packet must contain a
service name which indicates the service requested by the client.
2.
PADO (PPPoE Active Discovery Offer):
When a PPPoE server receives a PADI
packet in its service range, it will send a PADO response packet. The PADO packet
must contain the server’s name, and a service name identical to the one in the PADI,
PPPoE Client
PPPoE Server
PADI
PADO
PADR
PADS
