DHCPv6 Confirm in DOCSIS networks

[Tore Anderson]

My cable provider just got included me in their IPv6 pilot. One of the
first things I noticed when testing (using a computer directly attached
to the cable modem) was that DHCPv6 Confirm messages went unanswered.
The first time I connected went fast, while all subsequent connections
(e.g. after resuming from suspend) was slow, as the Confirm request had
to time out before information from the cached lease was used.

I understood from my provider that the likely cause was that their Cisco
CNR DHCPv6 server did not support DHCPv6 Confirm, and they also pointed
me to the following UNH-IOL document, which says «Transmission of DHCPv6
Confirm message is not expected on a DOCSIS WAN network»:

https://www.iol.unh.edu/services/testing/ipv6/grouptest/white_papers/CPE_IPv6_Test_Event_Whitepaper.pdf

This strikes me as rather strange - as far as I can tell, the DHCPv6
client has no way of determining if the Ethernet interface is running on
is connected to a DOCSIS modem or something else, so I don't see how it
could possibly selectively disable the use of Confirm in the case of DOCSIS.

Does anyone have more information on why DHCPv6 Confirm wouldn't be
expected and supported in DOCSIS networks? (Does it work in Comcast's
network?)

-- 
Tore Anderson
Redpill Linpro AS - http://www.redpill-linpro.com