ModemLPA
and router-modem-integration work.

Modems that vary link speeds or lose their connectivity can't tell other devices that their links have changed. We have been trying to improve this situation by designing protocols that allow modems to tell other devices, such as routers, about changes.

Our ModemLPA design has a proof-of-concept packet generator. ModemLPA code is available, along with some internet-drafts and documentation:

For some context describing the overall problem, see:

Approaches from others in this problem space include radio extensions for PPPoE links, and the Dynamic Link Exchange Protocol (DLEP).

Lloyd Wood (lloydwood@users.sourceforge.net))