IPv6 prefixes longer then /64: are they possible in DOCSIS networks?

Wed Nov 30 16:54:10 UTC 2011

>From a requirements point of view I am not sure I would enforce these sort
of restrictions.

John

On 11/29/11 6:59 AM, "Dmitry Cherkasov" <doctorchd at gmail.com> wrote:

>John,
>
>I am determining technical requirements to IPv6 provisioning system
>for DOCSIS networks and I am deciding if it is worth to restrict user
>to use not less then /64 networks on cable interface. It is obvious
>that no true economy of IP addresses can be achieved with increasing
>prefix length above 64 bits.
>
>As for using EUI-64, unlike random or sequential generation it
>provides predictable results that may be desired, e.g. for tracking
>some device migration between different networks.
>
>Dmitry Cherkasov
>
>
>
>2011/11/29 Brzozowski, John <John_Brzozowski at cable.comcast.com>:
>> Dmitry,
>>
>>
>> You could consider the use of prefixes longer than the /64 on CMTS
>> interfaces, however, it is not clear to me why this would be done.
>> Further, most DHCPv6 implementations do not require that the generated
>> IPv6 address be eui-64 based.  A randomized algorithm could also be
>>used.
>> Another consideration is what happens after IPv6 is used for addressing
>> cable modems.  What happens when you want to address CPE or CPE routers?
>> You are right back to /64 or shorter depending on the type of device
>>being
>> provisioned.
>>
>> FWIW - we have found that there are distinct benefits to using IPv6
>>beyond
>> the amount of addresses that are available.  The use of /64 is tightly
>> coupled with these benefits.
>>
>> Can you elaborate as to why one would want to or need to use prefixes
>> longer than /64?
>>
>> John
>>
>> On 11/28/11 6:37 AM, "Dmitry Cherkasov" <doctorchd at gmail.com> wrote:
>>
>>>Hello everybody,
>>>
>>>It is commonly agreed that /64 is maximal length for LANs because if
>>>we use longer prefix we introduce conflict with stateless address
>>>autoconfiguration (SLAAC) based on EUI-64 spec. But  SLAAC is not used
>>>in DOCSIS networks. So there seems to be no objections to use smaller
>>>networks per cable interfaces of CMTS. I was not able to find any
>>>recommendations anywhere including Cable Labs specs for using
>>>prefixes not greater then /64 in DOCSIS networks. Some tech from ISP
>>>assumed that DHCPv6 server may generate interface ID part of IPv6
>>>address similarly to EUI-64 so MAC address of the device can easily be
>>>obtained from its IPv6 address, but this does not seem like convincing
>>>argument. What do you think?
>>>
>>>
>>>Dmitry Cherkasov
>>>
>>
>