DoD IP Space

Owen DeLong owen at
Thu Feb 11 07:33:24 UTC 2021

> On Feb 10, 2021, at 09:50 , Doug Barton <dougb at> wrote:
> On 2/10/21 5:56 AM, Ca By wrote>
>> The 3 cellular networks in the usa, 100m subs each, use ipv6 to uniquely address customers. And in the case of ims (telephony on a celluar), it is ipv6-only, afaik.
> So that answers the question of how to scale networks past what can be done with 1918 space. Although why the phones would need to talk directly to each other, I can't imagine.

Ideally SIP does the call setup and registration of the phone’s DIDN to to IP mapping, but once call setup is completed, ideal is a pair of RTP streams between the phones directly (modulo annoying CALEA provisions getting in the way).

> I also reject the premise that any org, no matter how large, needs to uniquely number every endpoint. When I was doing IPAM for a living, not allowing the workstations in Tucson to talk to the printers in Singapore was considered a feature. I even had one customer who wanted the printers to all have the same (1918) IP address in every office because they had a lot of sales people who traveled between offices who couldn't handle reconfiguring every time they visited a new location. I thought it was a little too precious personally, but the customer is always right.  :)

Unique numbering doesn’t mean connectivity, it means the possibility of allowing connectivity.

There’s. also the transitive issue… If A needs to talk to B and B needs to talk to C, then having A and C in the same address space is a problem, even if A doesn’t need to talk to C.

> Sure, it's easier to give every endpoint a unique address, but it is not a requirement, and probably isn't even a good idea. Spend a little time designing your network so that the things that need to talk to each other can, and the things that don't have to, can't. I did a lot of large multinational corporations using this type of design and never even came close to exhausting 1918 space.

It’s absolutely a good idea. Using address overloading to avoid the possibility of permitting connectivity is just bad design any way you slice it.

Oh, and no network design survives contact with the real world. The set of things that need to talk today are not the same set of things that will need to talk in 1 year, 5 years, 10 years, etc.

The accounting department will NEVER talk directly to the sales department until they do.


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