[ih] Fw: Dotted decimal notation

[Barbara Denny]

 I thought I hit reply all. Apologize for any duplicates.

barbara
   ----- Forwarded Message ----- From: Barbara Denny via Internet-history <internet-history at elists.isoc.org>To: "greenwald at cis.upenn.edu" <greenwald at cis.upenn.edu>; Vint Cerf <vint at google.com>Cc: Nelson H. F. Beebe via Internet-history <internet-history at elists.isoc.org>; Michael Greenwald <mbgreen at seas.upenn.edu>Sent: Monday, December 28, 2020, 06:27:00 PM PSTSubject: Re: [ih] Dotted decimal notation
  Not sure if anyone is interested but I found a document written for the Army dated November 1977 that shows internet and packet radio headers.  In a very early internet header the first byte is identified as the network and the last 3 bytes are described as source or destination host (not all the fields in the current IPv4 header are present and the ordering is different). 
If interested the document is in dtic:  Army Packet Radio Network Protocol Study by DE Rubin.
barbara
    On Monday, December 28, 2020, 04:58:37 PM PST, Vint Cerf via Internet-history <internet-history at elists.isoc.org> wrote:  
 
 i believe michael is correct.

v


On Mon, Dec 28, 2020 at 7:51 PM Michael Greenwald via Internet-history <
internet-history at elists.isoc.org> wrote:

> On 2020-12-28 16:35, Brian E Carpenter via Internet-history wrote:
> > Thanks for the various replies. I wasn't there, but clearly some magic
> > happened between the 8-bit network numbers in RFC776 (January 1981) and
> > the emergence of Class A, B, C addressing in RFC790 (September 1981),
> > and that called for some new notation such as dotted decimal.
>
> For what it's worth, I am fairly certain that I was
> parsing dotted decimal addrs (10.0.0.6) "long" before
> class A, B, or C addresses existed. The rough description
> that I got from Dave Clark in 79-ish was that the
> first byte was the network, and the remaining 24 bits
> were structured as subnet/host in some network-specific
> way (8 bit imp/... n bit host, or 16 bit subnet/8 bit host,
> or whatever). And for debugging/tracing on multics, I
> was definitely printing IP addrs as 4 dotted decimal
> numbers, even though I really, really, didn't like them.
> So I assume that the dotted-decimal notation was in use
> in more than one place, already, by 79.
>
> >
> > That magic is not well documented in the RFC series, but in IEN175,
> > reporting on a January 1981 meeting, we find that
> >      "Vint Cerf led a further discussion on addressing.  The main
> > focus
> >      was on the tradeoff between a flat address space and a
> >      hierarchical one...
> >      Vint suggests that we have both in one!  Let an address be
> >      composed of two parts: a hierarchical address (called an address)
> >      and a flat address (called an identifier)."
> >
> > I guess that became Class A, B, C by September, via IEN177, but it also
> > accurately describes IPv6 addressing.
> >
> > Regards
> >    Brian Carpenter
> >
> > On 29-Dec-20 10:54, Jack Haverty via Internet-history wrote:
> >> IIRC, this convention was created over time by a coalescence of "rough
> >> consensus and running code" as the early user programs (Telnet and
> >> FTP)
> >> were being rewritten to use TCP instead of NCP, so it would have been
> >> during the late 70s.  On the ARPANET, e.g., when a particular Telnet,
> >> you would type "O <host>/<imp>", e.g., 1/6 to connect to MIT-DMS, host
> >> 1
> >> on IMP 6, or "O 70" which was the equivalent.  Something new was
> >> needed
> >> for specifying 32-bit IP addresses.
> >>
> >> Dotted quad was one early approach, where the 4 numbers could be
> >> either
> >> octal, if they had a leading zero, and otherwise decimal.
> >> A leading 0 indicated that the number was octal - also a common
> >> convention in programming languages at the time.
> >>
> >> The "dotted decimal" convention evolved from the "dotted quad", with
> >> the
> >> difference being that the numbers in the "...decimal" form were of
> >> course always decimal, regardless of the presence of a leading zero.
> >>
> >> I believe all of these forms were created as various people wrote user
> >> programs.  The notation is really a design decision of the user
> >> interface, converting typed IP addresses into the appropriate 32-bit
> >> fields for the underlying TCP code.
> >>
> >> Some people liked decimal numbers, others liked octal.
> >>
> >> One particularly irritating choice was pure decimal, i.e., a 32-bit
> >> number represented in decimal (no dotted quad).  The early SRI TIU
> >> (terminal concentrator) required the user to input decimal numbers,
> >> which were annoyingly difficult to calculate.    E.g., 10.0.0.5,
> >> easily
> >> recognized as Host 0 on ARPANET IMP 5, had to be typed in its 32-bit
> >> decimal format when specifying what remote computer the user wanted to
> >> access.  It was difficult to do such calculations in your head; I
> >> remember pulling out a calculator to create the appropriate many-digit
> >> decimal number.
> >>
> >> Eventually the "dotted quad" notation reached rough consensus and many
> >> host implementations of user apps (Telnet, FTP) permitted that form of
> >> specifying a target host.
> >>
> >> The "dotted decimal" convention eventually superceded the "dotted
> >> quad"
> >> notation because the quad form was often confusing.
> >>
> >> E.g., "ISIF in dotted decimal is 010.002.000.052, or 10.2.0.52", where
> >> leading zeroes are ignored.  But in dotted quad,
> >> 010.002.000.052 and 10.2.0.52 would not be equivalent.  010 would be
> >> network 8 rather than 10, and 052 would be 42 instead of 52.
> >>
> >> I don't remember who first produced dotted decimal though.  I think
> >> you'd have to look at the applications programs of the time (FTP,
> >> Telnet) to see what each used for its UI.
> >>
> >> /Jack
> >>
> >>
> >> On 12/28/20 12:55 PM, Brian E Carpenter via Internet-history wrote:
> >>> Can anyone recall when and by whom the dotted decimal notation for
> >>> IPv4
> >>> addresses was invented? This text first appeared in RFC820 (January
> >>> 1983):
> >>>
> >>>    One commonly used notation for internet host addresses divides the
> >>>    32-bit address into four 8-bit fields and specifies the value of
> >>> each
> >>>    field as a decimal number with the fields separated by periods.
> >>> This
> >>>    is called the "dotted decimal" notation.  For example, the
> >>> internet
> >>>    address of ISIF in dotted decimal is 010.002.000.052, or
> >>> 10.2.0.52.
> >>>
> >>> The leading zeroes are not considered valid these days.
> >>>
> >>> Thanks
> >>>    Brian Carpenter
> >>
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