So long as we are running down this rabbit hole…. ☺ My very original comment was “if this is a use case document, why is this concept in here with no associated use case for why I would need it? Could we have a use case please”
As the comment referred to multiple subnets, I would then observe that as far as IP is concerned, a subnet traditionally corresponds to a broadcast domain. These days I do not necessarily need to implement it via traditional bridging, and a lot of traditional discovery is changing to being database driven configuration. But I would have no trouble noting that a broadcast domain that also corresponds to a subnet has useful properties at a bunch of levels as a subnet prefix/mask becomes a convenient shorthand for the set, although a VNI is an even more convenient shorthand ☺ But if I want to run a single network as if it were a subnet using established tools, fine…. What I am less clear on is constructing a virtual network of multiple subnets and creating a virtual topology when AFAIK this does not get me much. Am I simply scaling a single community of interest to which common policies apply? IN which case most of the properties a broadcast domain gets me, I’d want to see at L3. Am I defining relationships between dissimilar communities of interest, which is wildly overloading the concept… As noted above policy could equally be expressed as VNI relationships, which likely is an equally useful abstraction. I hope this is clear Dave From: Joe Touch [mailto:[email protected]] Sent: Saturday, August 13, 2016 10:30 AM To: David Allan I <[email protected]> Cc: [email protected]; Bocci, Matthew (Nokia - GB) <[email protected]> Subject: Re: [nvo3] FW: Call for interest on NVO3 use case draft On 8/13/2016 9:52 AM, David Allan I wrote: Hi Joe And the use case for wanting to do subnet emulation is….? You want the properties of a subnet and/or to emulate the behavior of a shared link, i.e., to limit the scope of various protocols, including IP routing, IPv6 automatic addressing, L2 address translation (virtualizing L2 underneath a virtual L3 is needed to support revisitation, where a single node participates multiple times in an overlay), and basically any subnet-based resource discovery. Joe That‘s my question Dave From: Joe Touch [mailto:[email protected]] Sent: Friday, August 12, 2016 8:20 PM To: David Allan I <[email protected]><mailto:[email protected]> Cc: [email protected]<mailto:[email protected]>; Bocci, Matthew (Nokia - GB) <[email protected]><mailto:[email protected]> Subject: Re: [nvo3] FW: Call for interest on NVO3 use case draft The typical use case is to support subnet emulation, e.g., a group of links over which broadcast is emulated as with LANE. On Aug 12, 2016, at 7:11 PM, David Allan I <[email protected]<mailto:[email protected]>> wrote: My point would be that introducing additional complexity in an overlay should have a use case associate with it. It would not be something you would do gratuitously…. SO I’m looking for the draft to provide a use case for this vs. simply mentioning subnetting without any context ☺ Cheers Dave From: nvo3 [mailto:[email protected]] On Behalf Of Joe Touch Sent: Friday, August 12, 2016 5:07 PM To: David Allan I <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]>; Bocci, Matthew (Nokia - GB) <[email protected]<mailto:[email protected]>> Subject: Re: [nvo3] FW: Call for interest on NVO3 use case draft On 8/12/2016 4:16 PM, David Allan I wrote: 4.2 Why I would subnet my overlay could use some explanation. I normally think of subnetting as a convenient address summarization technique dependent on topology, and with an overlay I don’t have a topology. The topology of an overlay is determined by its tunnels, just as the topology of the underlying net is determined by its links. A subnet in an overlay corresponds either to a single multipoint tunnel or to a set of tunnels that transparently acts as such - just as a subnet in the Internet base network corresponds to a shared access link or a set of links that transparently act as such (e.g., switched ethernet). Joe
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