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1) The RAC decided on a quadrant for assigning the CIDs from. It seemed like it was most likely that those doing local administration have chosen to start from the bottom end (i.e. all zeros in the upper bytes except for the local/global bit). So they didn’t choose that quadrant for CID assignments. IIRC, it was also mentioned that perhaps some local administrators had started from the top of the address space. So one of the middle quadrants was selected for CIDs as it is less likely to conflict with existing local administration of MAC addresses.
The choice of the address blocks for the FCoE protocol didn’t enter into the RAC decision – at least I don’t recall that from discussion. That happens to be one case of a protocol that defines the use of fixed blocks but probably not the only case. Some virtualization vendors also use fixed blocks from local address space. So it didn’t seem possible to choose a quadrant that aligned with existing use of local address blocks for protocols and that wasn’t a factor. If FCoE’s usage had fallen within the CID range, then I would have asked that those CIDs be assigned to INCITS T11 to grandfather the use.
There has been some discussion of whether to create a listing of those blocks with use that predates CID creation so that people (e.g. those wanting to do local administration) can look up the use and avoid it.
One quadrant seems adequate for local address administration and that leaves two quadrants for reserving for future use.
That does leave the possibility of a large random address assignment space with up to 44 bits of randomness. I stated some concerns about the proposal in 802.11 for this. Even with 44 or 46 bits, there is a potential for address conflicts occurring – looking at a single network, they would be extremely rare, but multiplied by all the networks and all the operating time, conflicts will occur at times and there doesn’t seem to be any mechanism proposed for conflict detection and resolution. Once one has a mechanism for conflict detection and resolution, why does one need such a large space? The proposal that currently proposes using the whole of the local address space for random assignment potentially conflicting with any other use of that space has no accompanying justification for why that is okay.
2) The statement in IEEE Std 802 remains true in intent. The address assignments made by protocols using CID blocks will be local assignments and will have a global uniqueness requirement. The text will need a bit of change because now the IEEE RA is assigning values for some of the local space. I.e. “IEEE RA-assigned values” referred to the “IEEE RA-assigned OUI values”. As with many other standards, one will need to look at each use of OUI and decide whether it should be “OUI” or “OUI or CID” depending on the context.
3) Part of the purpose of the amendment is to provide better guidance on the use of local address space. There is very little said about it anywhere. One consequence of this is that it has had very little usage. This amendment would unlock that potential by providing that guidance and would also protect the much more stressed global address space.
Roger, and others:
Please see inline comments, responses to questions below. (Again, everything is personal opinion, not RAC position.)
On Oct 8, 2014, at 12:02 PM, Roger Marks <email@example.com> wrote:
I share many of Dan's concerns about partitioning the local space.
<RMG> If a vendor for example is creating virtual machines, if they use their CID, it will by definition be unique from any other vendor using their CID as the basis for creating local addresses for virtualization or any other purpose. There doesn’t have to be a single address administration function. Other thoughts of RAC members (no policy on any of this that I recall):
1. If only a portion of the CID space is used for automated assignment, then we can reserve another portion to be the “wild west” where a Local Address administrator still has free reign.
2. We can gather up and publish somehow a list of local addresses that people have assumed to be usable. Some local addresses are specified in standards.
3. We can consider giving priority to current OUI assignees to get the corresponding CID (numbers only differing by the U/L bit). This would legitimize those users that assumed (they had rights to do this). (Big debate should we reaward someone that just assumed rights that weren’t expressly granted?) BTW, The RAC administrator just received a question last month stating the assumption that they had rights to flip the U/L bit of an assigned OUI and nobody else would be assigning a Local Address with that value—nothing that RAC policy suggests they could assume but not uncommon.
<RMG> What of any of this RAC thinking/discussion would be included in the p802c draft is not an issue for the PAR, but rather for draft development and balloting. BTW, it wasn’t only RAC thinking, but 802.1 and IETF that contributed to launching the CID recognizing possibilities for use in automated local address creation.
<RMG> On the privacy point, a CID based address is better than an EUI used as a MAC address as it is not repetitively used by a device (24-bits could still effectively be random) from the snooping point of view. If it were turned around and the CID is one used by the local address administrator, then the local MAC address that a device is using tell you nothing about that device. Using CID in diagnosis was not a consideration as far as I recall either during RAC discussions or in possible protocols I’ve heard described.
<RMG> If there were multiple DHCP devices in your house that didn’t communicate, that would be one way to allow both DHCP devices to not assign duplicates. I believe Fibre Channel Over Ethernet has sufficient specification (like DHCP) so that this would not be needed, but if the RA assigns the appropriate CID to FCOE, then no virtulization vendor or Internet of Things vendor would be assigning duplicates with the FCOE application.
<RMG> There are also possibilities that the function is more that of a software vendor, operator or other rather than a hardware manufacturer. (Though CID use in many of these cases is not for MAC addresses but rather for Context Dependent Identifiers.)
(b) The local network administrator? This seems to be like saying that every locally-assigned DHCP address in my house should have some bits that are unique to my house. What use is that? Local is local; what good is making it partially global?
<RMG> The most consistent policy for use of the local address space is that a local address administrator would assure no duplicates were created. That has existed since the early 1980s. IBM proposals back then indicated a preference for only using local addresses for 802.5 (16-bit ring number and 32-bit node number). That would have operated under this broad rule for the local address administrator. Perhaps I’m missing your point with the DHCP example here.
(c) An operator? For example, a gas meter has a gas company CID and an electrical meter has a power company CID on the same LAN. Seems like a problem better solved by VLAN,.
<RMG> VLAN isn’t the answer to duplicate addresses. I don’t recall VLANs being part of RAC considerations though.
(d) Something else?
<RMG> Where there is no standard to govern things, the CID allows private protocols that do not have to cooperate with other protocols. Obviously if p802c is successful, then it will be
referenced by other standards and be used by private protocols rather than just picking local addresses for the application as is now sometimes done. CID of course has non-address uses that can reduce the consumption of OUIs. For example, some standards
specify use of an OUI for non-address applications. I would guess though that this was not part of your concern here.
<RMG> Lots of possibilities here. How about 44 bits? One quadrant of the local space for the “wild west”, one for CID based automated assignment, one for … Realistically, the problem here is how to best accommodate the fact that the entire space is the “wild west” today, no rules other than some local administrator being responsible for preventing duplicates, but reality being that some uses of the local address space are in use. From my perspective, the RAC is really serious about not declaring other legacy uses “illegal”, something 46-bits probably could come closer to doing. I believe the RAC consensus is that any local address structuring will take years to get pushed into the marketplace. We started that by getting appropriate warning into IETF descriptions of 802 addressing and OUI and CID. We tried to get it into the revision of Std 802. We will work to get things tightened up in many IEEE standards that use the OUI registry especially other IEEE standards that use 802 addressing. But this is and will be a long process not solved by p802c even though I believe p802c helps with a solution. Any proposal that ignores the reality of legacy use and simply assumes local addresses are not in use, I believe is flawed, whether that assumption is in 802 or IETF or were to become a property of any standard that attempts to jump into the local address space.
My personal opinion is the primary RAC responsibility is to ensure the viability of its registries. The two I worry about most are OUI and EtherType. I also believe that IEEE Std 802
is the right place to standardize 802 style MAC addresses. The two are related but there is an important distinction in responsibilities. An IEEE 802c amendment will have been subjected to a balloting process open to all interested parties. A RAC policy
isn’t subject to the same process.
<RMG> I disagree in principle. Such details are for a project to decide. To me, is there a reasonable solution (technical and economic feasibility) to bring structure to the local address space and make local addresses more usable for IoT, virtulization, etc. is the requirement for approving a PAR. Sometimes we write the PAR to standardize a solution, but that is not IEEE-SA policy. The PAR serves as an announcement to the world of activity being initiated to all interested parties, in other words, a PAR to address a problem or opportunity is really what is intended by IEEE-SA process. I’m expect I’ve overstated your position here, and I’ll leave it to the PAR proponents to accommodate provision of more detail.
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