Hi Joe, Dave, dear all, I think that the term “subnet” is indeed only defined in a context sensitive way.
Unfortunately there is no distinction made between a L2-subnet (aka a broadcast domain, or a MEF EVC, or o broadcast domain equivalent achieved without broadcast such as EVPN) and a L3-subnet (the object that does not appear in any information model that I am aware of, but which has a size which is defined by a subnet-mask and which supports the use case of “change the IP-address range assigned to that subnet”. Part of the reason for complexity is the lack of a proper definition of this object in the information model. If I am wrong – I would be happy to be corrected by someone who can point me to an authoritative definition of the term subnet as an object that supports the use case “change address range assigned to subnet” without specifying how the subnet is built as layer 2 construct (e.g. as Ethernet yellow cable, VLAN in a Switched Ethernet domain, VXLAN overlay, EVPN, MEF EVC or ATM point to point link). Thanks to OpenStack for finally fixing the problem by introducing the method “create network”, which creates – exactly – this missing object in an abstract way. So Dave’s question is very valid, simply because the term “subnetting” is not properly defined – unless the authors point to a reference RFC where the term is defined in an authoritative way. Lothar Von: nvo3 [mailto:[email protected]] Im Auftrag von Joe Touch Gesendet: Samstag, 13. August 2016 19:30 An: David Allan I <[email protected]> Cc: Bocci, Matthew (Nokia - GB) <[email protected]>; [email protected] Betreff: 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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