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IPv4 Addresses: 5% Left

 
 
victor
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      10-21-2010
On 21/10/2010 5:41 p.m., Matty F wrote:
> On Oct 21, 12:48 pm, Lawrence D'Oliveiro<l...@geek-
> central.gen.new_zealand> wrote:
>> In message
>> <(E-Mail Removed)>, Matty F
>> wrote:
>>
>>> Why didn't they use IPv6 in the first place?

>>
>> Were talking pre-PC era, back when computers, at least ones powerful
>> enought to be worth networking, were hefty boxes that had to live in their
>> own special rooms. Nobody ever thought wed have a billion computers like
>> that. And indeed, we never did.

>
> I invented a principle (but somebody else may have thought of it
> first) that when you are designing something, assume that it is going
> to succeed, and design accordingly to allow it to be scaled up.


Its a principle invented by a Mr I M Smug known as "hindsight".
 
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John Little
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      10-22-2010
On Oct 20, 9:45*pm, Lawrence D'Oliveiro <l...@geek-
central.gen.new_zealand> wrote:

> Given that IPv6 has room for roughly the same number of addresses as the
> estimated number of atoms in the entire observable Universe...


That's an exaggeration. 2^128 is about 3 x 10^38, cricket ground for
number of atoms is 10^80.
(See http://en.wikipedia.org/wiki/Observa...atter_content).
Just 41 orders of magnitude...

Also, subnets are always 64 bits in IPv6, drastically reducing
utilization of the address space.

Regards, John
 
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John Little
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      10-22-2010
Lawrence said:
> >>> math.log(2 ** 128, 3)

>
> 80.75900845714655


What's that 3 for? What relevance is a log to base of 3?

>>> math.log(2 ** 128, 10)

38.531839444989586
 
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Matty F
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      10-22-2010
On Oct 22, 10:19 am, victor <(E-Mail Removed)> wrote:
> On 21/10/2010 5:41 p.m., Matty F wrote:
>
>
>
> > On Oct 21, 12:48 pm, Lawrence D'Oliveiro<l...@geek-
> > central.gen.new_zealand> wrote:
> >> In message
> >> <(E-Mail Removed)>, Matty F
> >> wrote:

>
> >>> Why didn't they use IPv6 in the first place?

>
> >> Were talking pre-PC era, back when computers, at least ones powerful
> >> enought to be worth networking, were hefty boxes that had to live in their
> >> own special rooms. Nobody ever thought wed have a billion computers like
> >> that. And indeed, we never did.

>
> > I invented a principle (but somebody else may have thought of it
> > first) that when you are designing something, assume that it is going
> > to succeed, and design accordingly to allow it to be scaled up.

>
> Its a principle invented by a Mr I M Smug known as "hindsight".


It's in Systems Analysis 101, if a field is likely to expand in size,
have a field length on it.
 
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Lawrence D'Oliveiro
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      10-22-2010
In message
<(E-Mail Removed)>, John
Little wrote:

> Also, subnets are always 64 bits in IPv6, drastically reducing
> utilization of the address space.


No they’re not. They learned their lesson from the “class” restrictions of
IPv4.
 
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Lawrence D'Oliveiro
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      10-22-2010
In message
<(E-Mail Removed)>, Matty F
wrote:

> It's in Systems Analysis 101, if a field is likely to expand in size,
> have a field length on it.


Does that mean you should have a length field for the field length field,
just in case?
 
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Matty F
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      10-22-2010
On Oct 23, 11:51 am, Lawrence D'Oliveiro <l...@geek-
central.gen.new_zealand> wrote:
> In message
> <(E-Mail Removed)>, Matty F
> wrote:
>
> > It's in Systems Analysis 101, if a field is likely to expand in size,
> > have a field length on it.

>
> Does that mean you should have a length field for the field length field,
> just in case?


Yes, if you are going to have fields longer than 255 bytes. I never
saw fields longer than that in commercial systems. Longer fields could
probably be broken up into smaller fields of max 255 bytes.
 
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Ted
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      10-22-2010
On Fri, 22 Oct 2010 16:01:13 -0700 (PDT), Matty F
<(E-Mail Removed)> wrote:

>On Oct 23, 11:51 am, Lawrence D'Oliveiro <l...@geek-
>central.gen.new_zealand> wrote:
>> In message
>> <(E-Mail Removed)>, Matty F
>> wrote:
>>
>> > It's in Systems Analysis 101, if a field is likely to expand in size,
>> > have a field length on it.

>>
>> Does that mean you should have a length field for the field length field,
>> just in case?

>
>Yes, if you are going to have fields longer than 255 bytes. I never
>saw fields longer than that in commercial systems. Longer fields could
>probably be broken up into smaller fields of max 255 bytes.


Or have variable length fields. Something like UTF-8, but endless.
 
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Matty F
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Posts: n/a
 
      10-22-2010
On Oct 21, 7:30 pm, Lawrence D'Oliveiro <l...@geek-
central.gen.new_zealand> wrote:
> In message
> <(E-Mail Removed)>, Matty F
> wrote:
>
>
>
> > On Oct 21, 12:48 pm, Lawrence D'Oliveiro
> > <(E-Mail Removed)_zealand> wrote:

>
> >> In message
> >> <(E-Mail Removed)>, Matty
> >> F wrote:

>
> >>> Why didn't they use IPv6 in the first place?

>
> >> Were talking pre-PC era, back when computers, at least ones powerful
> >> enought to be worth networking, were hefty boxes that had to live in
> >> their own special rooms. Nobody ever thought wed have a billion
> >> computers like that. And indeed, we never did.

>
> > I invented a principle (but somebody else may have thought of it
> > first) that when you are designing something, assume that it is going
> > to succeed, and design accordingly to allow it to be scaled up.

>
> So how scalable were your systems? Could they network a billion machines?


I suppose there always has to be a limit somewhere.
In the early 1980s we allowed the addressing for our database to reach
8 Terabytes.This was in the days when disk drives for PCs were seldom
bigger than 256 Megabytes. I never imagined that a commercial system
would need more than 8 TB. So I allowed for a size increase of 30,000
times over a 30 year period, and that was not enough. However it was a
simple conversion to copy the database with another byte of
addressing. The database did have a 1 byte length for the length of
the address field. So the database could never be bigger than the
number contained in a 255 byte binary field. I believe that is enough.

I designed and implemented a three dimensional spreadsheet whch could
have 2,000,000,000 rows, columns and another dimension. Each cell
could contain a query that could examine a simple file of up to
2,000,000,000 records.
Numbers could have almost any editing desired, up to 64 characters in
length. Not bad for the1980s. It's still larger than Excel.
 
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Murray Symon
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Posts: n/a
 
      10-23-2010
Lawrence D'Oliveiro wrote:

> In message
> <(E-Mail Removed)>, Matty
> F wrote:
>
>> It's in Systems Analysis 101, if a field is likely to expand in size,
>> have a field length on it.

>
> Does that mean you should have a length field for the field length field,
> just in case?


DER has a scheme that handles that pretty well.
It is TLV with a variable Length field.
 
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