HP-UX PPP Enhancements - PPPoE and PPPv6 for TOUR 1.0

hp-ux ppp enhancements – pppoe and pppv6 white paper

August 2003

protocol overview

Typically, a PPPoE session comprises two peers communicating over an

Ethernet link. Each peer must learn the Ethernet address of the remote peer

and establish a unique session identifier that identifies the PPPoE session

between the peers. The following diagram depicts how the PPPoE client and

the server, on the same link, communicate with each other.

fig 1: When Client and Server Are on the Same Link

An optional relay is required when there is a router between the PPPoE client

and the server. In such cases, the relay receives packets from the clients and

transmits them on the other link to the server and from the server to the client.

See fig 2 for information on how the client connects to the server via a relay.

fig 2: When Client and Server Are on Different Links

PPPoE Session

Each PPPoE session includes the following stages:

 Discovery stage

PPPoE functions as a client/server model in the discovery stage. Before

a host tries to initiate a PPP session, it searches for a suitable PPPoE

server (access concentrator) that can provide the services required by

the host. The host then learns the server's Media Access Control (MAC)

address and a unique session number called the session ID. During this

process, if the host finds more than one access concentrator, it chooses