[ih] The classful <net>.<host> IPv4 address format

[Vint Cerf]

12 would be correct in octal
v


On Sun, Sep 14, 2025 at 6:40 PM Barbara Denny via Internet-history <
internet-history at elists.isoc.org> wrote:

>  I always thought the ARPAnet was number 10.  On page 1 in this document,
> the example says 12. Am I missing something? I haven't read the entire
> document.
> barbara
>     On Sunday, September 14, 2025 at 05:57:16 AM PDT, Craig Partridge via
> Internet-history <internet-history at elists.isoc.org> wrote:
>
>  IEN 21 (TCP v. 3) specifies a network.host.port format, which I suspect is
> the origin of the net.host form.
>
> https://www.rfc-editor.org/ien/ien21.pdf
>
> Craig
>
> On Sun, Sep 14, 2025 at 6:21 AM Michael Kjörling via Internet-history <
> internet-history at elists.isoc.org> wrote:
>
> > Every once in a while I see people being surprised that IPv4 addresses
> > can be expressed in formats other than dotted-decimal-quad; more
> > specifically, in classful-style <net>.<host> (where net and host can
> > add up to less than four octets) or even single-large-integer format.
> >
> > I am _almost_ certain that I have seen an early IP or TCP RFC which
> > actually describes this representation, but have been unable to locate
> > that.
> >
> > Can anyone point me at an authoritative source where the
> > dotted-not-quad textual IPv4 address representation format is defined
> > or at least described? Thanks!
> >
> > --
> > Michael Kjörling
> > 🔗 https://michael.kjorling.se
>
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