DOCSIS 3.0 & PPPoE/L2TP compatibility

iptech iptech at
Mon Jul 30 12:33:51 UTC 2012


We are a small ISP and have a setup in place with the local cable 
company for terminating their users via L2TP for Internet access. 
However they have just announced to us that they are moving to a DOCSIS 
3.0 compliant setup, and this standard no longer supports PPPoE via 
L2TP, and can now only offer PPTP for terminating with us.

We have already begun replacing our Cisco 7206VXR LNS devices with Cisco 
ASR 1Ks and as you will be aware the older 7206 can do both L2TP and 
PPTP, whereas the ASR1k can do only L2TP. I do not have any experience 
in the cable arena, but from what I have read in the DOCSIS standards, 
each version has maintained backwards compatibility, therefore I am very 
surprised our CableCo has claimed they cannot do PPPoE/L2TP anymore.

The CMTS they are currently using is a Cisco, and now they are moving to 
a new ARRIS CMTS. I have not been able to find any information on this 
device and what it can do or not. With the ASR1K marked as the natural 
upgrade path for LNS functions, therefore I cannot believe that it is 
not fully compatible with DOCSIS 3.0.

 From what I can tell the only way to accommodate the new CMTS PPTP 
connections will be to terminate them on the legacy 7206VXR, which at 
the end of the day is a backwards step. I would greatly appreciate if 
anyone can give me any pointers and/or suggestions on this matter, so I 
can understand it and move it forward.

FYI: The driver for the CMTS upgrades is to offer higher bandwidth 
access speeds 15mb-20mb.

Thank you.

More information about the NANOG mailing list