Sorry for the late reply.
Le 19/02/2013 22:08, joel jaeggli a écrit :
On 2/19/13 12:40 PM, Alexandru Petrescu wrote:
I think I may need to actually better expose the problem: how to form
IPv6 addresses for vehicles. (yes we know these already exist: DHPCv6,
PRefix Delegation on cellular, stateless autoconf, NAT, NPT, 64share).
One of the questions I have in that context what special property of
cars make them need a new method?
Well they're different than Ethernet interfaces. One could have several
Ethernet interfaces in a single car. And, cars have their globally
unique space of identifiers which is not EUI-48.
When one tries to make an IPv6 addressing architecture for vehicles one
goes into planning which could quickly overcome the space of IPv6.
There are very many hurdles to a simple straightforward IPv6 address
planning for vehicles.
1 - At most 2^78 vehicles may exist.
There may be not enough space in IPv6 addressing architecture space
to uniquely distinguish between all past current and future
vehicles.
Theoretically, the total number of vehicles possible is given by
interpreting the semantics of VIN (17 "digits", some holding
max 33 values, others less). Under optimistic interpretations, a
trivial 1-to-1 conversion from VIN "characters" space to bit-space
of an IPv6 address leads to 78bits.
(the structure of VIN is :
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| WMI | VDS | VIS |
+--------+-----------------+-----------------------+
but more details on the net searching Vehicle Identification
Numbers)
It's hard to imagine that the first 78 bits of an IPv6 address
designate one particular vehicle. The IPv6 address structure
ofers something like a maximum of 61bits to designate one
particular subnet. And, in a vehicle there is often more than one
subnet.
2 - the prefixes obtained from Registries, or from ISP (which one
should I try first?) may come with a price tag. The more vehicles,
the pricier the allocation.
3 - prefixes which are provider-assigned and/or provider independent
may introduce routing churn in the core of the Internet - if these
prefixes are numerous.
For these reasons, we still look closely at the use of ULAs (instead of
globally routable prefixes) and at how to generate these ULAs meaningfully.
Alex
Alex
Doug
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