PPPoE Intermediate Agent Configuration
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56. PPPoE Intermediate Agent
Configuration
56.1
Introduction to PPPoE Intermediate Agent
56.1.1
Brief Introduction to PPPoE
PPPoE (Point to Point Protocol over Ethernet) is a protocol that apply PPP protocol to
Ethernet. PPP protocol is a link layer protocol and supply a communication method of
point-to-point, it is usually selected by host dial-up link, for example the link is line dial-up.
PPP protocol is applied to Ethernet that means PPPoE protocol makes many hosts of
Ethernet to connect a remote access collector through one or multiple bridge devices. If
the remote access collector is broadband access server (BAS), it can supply broadband
access and accounting functions for these hosts, so PPPoE protocol is used to broadband
access authentication of Ethernet usually.
56.1.2
Introduction to PPPoE IA
Along with broadband access technique is rapidly developed, broadband access
network is also developing from strength to strength, but security problem gradually
becomes the focus, soever the clients or the access device and the network are faced
with security problem (especially from the client) in the current access network. Traditional
Ethernet user can not be identified, traced and located exactly, however in exoteric and
controllable network, identification and location are the basic character and requirement
for user, for example, when supplying the application that use user accounts to login, this
method supplied by PPPoE Intermediate Agent can availably avoid user accounts
embezzled.
There are two stages for PPPoE protocol work: discovery stage and session stage.
Discovery stage is used to obtain MAC address of the remote server to establish a
point-to-point link and a session ID with the server, and session stage uses this session ID
to communicate. PPPoE Intermediate Agent only relates to discovery stage, so we simply
introduce discovery stage.
There are four steps for discovery stage:
1. Client sends PADI packet: The first step, client uses broadcast address as
destination address and broadcast PADI (PPPoE Active Discovery Initiation)
packet to discover access collector in layer 2 network. Notice: This message