On 9/27/11 08:36 CDT, Roland Bless wrote:
Hi,
it seems that there is currently not much interest in ULA-Cs (centrally
assigned ULAs).
That interest varies significantly I would suggest you are correct int
he IETF and service provider worlds. However, in the enterprise and
manufacturing worlds I this there is more interest in the ULA model.
I came across several use cases, where manufacturers
(e.g, those of cars, airplanes, or smart metering environments)
would need internal/closed IPv6-based networks (maybe only for internal
control and management), that have no connection to the Internet.
For several reasons (esp. security) those networks
should operate isolated and independent from the Internet. In some cases
these products or installations may get merged, so prefix uniqueness
would be beneficial. Using locally assigned ULAs still bears the risk of
getting conflicts between manufacturers, esp. when considering the
number of manufacturers and products.
On the one hand it would be preferable for manufacturers to have an own
prefix for that purpose. Since every product with an on-board network
would need such a unique prefix, getting/requesting /48 ULAs per
product or installation doesn't seem to be appropriate.
On the other hand the currently defined ULA format is probably also not
very well-suited for that purpose, since it is intended to be used for
sites, but these products rarely require ~2^16 subnets, i.e., an 8 bit
subnet ID may be sufficient for most purposes. Thus, for this case the
currently defined ULA format is too restrictive requiring a 16-bit
subnet ID. Letting manufacturers ask for a large PI prefix from the
normal routing space does not make much sense either, since it is not
intended to be ever routed in the Internet.
Wouldn't it make more sense to define something similar to existing ULAs
along the lines of:
| 7 bits | 21 bits | 36 bits | 64 bits |
+--------+----------+--------------------+----------------------------+
| Prefix | OUID | OLA Prefix | Interface ID |
+--------+----------+--------------------+----------------------------+
Prefix: fixed, TBA, e.g., fa00::/7
OUID: Centrally assigned organizational unique ID
OLA Prefix: Organization locally assigned prefix, that consists
of a Product specific prefix ID (PID) and an n-bit subnet ID, e.g.:
| 7 bits | 21 bits | 36-n bits | n bits | 64 bits |
+--------+----------+-----------+--------+----------------------------+
| Prefix | OUID | PID |SubnetID| Interface ID |
+--------+----------+-----------+--------+----------------------------+
PID: Product specific prefix ID (should be unique across all products
under the same OUID).
Usually n=8 or larger, depending on the number of manufactured products
(in this case 2^28=268,435,456) and their expected lifetimes. So the
idea is to centrally assign the OUIDs and let the organizations assign
the PID. If the OLA prefix space is too small for a manufacturer (some
sell currently more than 10^7 units per year), he may request another
OUID, just like it is done for company_ID/OUIs for IEEE-based
addresses. Different sizes for OUID and the OLA prefix may be discussed
(using 22 bits for OUID), but I just wanted to get input first whether
this would be useful at all or why it may be definitely a bad idea
(except that companies may misuse these addresses for other purposes).
When saw this this morning my initially reaction was negative, however
I'm warming to the idea. However if we do something like this for the
manufacturing world we better move forward normal ULA-C for the
enterprise guys that want ULA otherwise you will quickly burn through
your 21 - bit OUI. It won't just be manufactures that use this form of
ULA (how about ULA-M, for ULA-Manufacturing) if it is created without a
more standard ULA-C available for the enterprise guys.
Regards,
Roland
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