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<div class="">This implies an IP allocation request that passes something other than a network/port to the IPAM subsystem.</div>
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What I forgot to mention in my previous email is that proposal #2 is basically a feature we are planning for our custom IPAM driver (without the routing piece). We allow arbitrary tagging of subnets with meta-data in our backend. We plan to enable the user
to utilize this information when making an IPAM request via a custom IPAM request type. However it would be a two step process - use the meta-data to find the network then use the network to get the IP.</div>
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<div class="">As a (gulp) third alternative, we should consider that the front network here is in essence a layer 3 domain, and we have modeled layer 3 domains as address scopes in Liberty. The user is essentially saying "give me an address that is routable
in this scope" - they don't care which actual subnet it gets allocated on. This is conceptually more in-line with [2] - modeling L3 domain separately from the existing Neutron concept of a network being a broadcast domain.</div>
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<div class="">Again, the issue is that when you ask for an address you tend to have quite a strong opinion of what that address should be if it's location-specific.<br class="">
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<div>An alternative that gives you more control than using an address scope would be to use a subnet pool. The more I think about this, it seems to me in that in this particular use case, all we are talking about is a grouping of subnets. This leads me to think
tying it to subnet pools rather than to a network, because you can group subnets arbitrarily (though a given subnet can be in only one pool).</div>
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<div>The issue is the often arbitrary and overloaded use of the word "network". This has already been defined as an L2 broadcast domain so I am not sure it is a good idea to change that at this time.</div>
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Fundamentally, however we associate the segments together, this comes down to a scheduling problem.
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<div class="">It's not *solely* a scheduling problem, and that is my issue with this statement (Assaf has been saying the same). You *can* solve this *exclusively* with scheduling (allocate the address up front, hope that the address has space for a VM with
all its constraints met) - but that solution is horrible; or you can solve this largely with allocation where scheduling helps to deal with pool exchaustion, where it is mainly another sort of problem but scheduling plays a part.<br class="">
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<div>Fair enough.</div>
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<div>John</div>
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