ADSL2/2+ PPP over L2TP Process Cycle

This is an overview for the process cycle for establishing a PPP session over a new L2TP tunnel between a LAC and LNS. A general rule of thumb is that everything is repeated. The CPE will go through PPP establishment and LCP with the LAC, then once the L2TP tunnel is built it can renegotiate LCP with the LNS if the LNS settings differ to the LAC (such as MRU size). So LCP will "run" again and then IPCP will run.

Long Version (click for original, © James Bensley and all that shit):

Short version:

 

These next two diagrams below are from BT, the lower one shows in more detail the steps involved for the end to end PPP set-up process whilst the upper on shows simply the protocol reach for PPP, LCP and IPCP.

PPP over BT Wholesale 21CN Source: BT SIN 472v6

 

PPP over BT Wholesale 20CN

References:
BT SIN 374v1p5
BT SIN 472v2p6


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