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Re: Arbitrary-length numbers

"Тони Стоев | Toni Stoev" <debian@tonistoev.info> writes:

> Why so, what is the gain? A promising example: use of arbitrary-length
> numbers in network addresses.  Node addresses can be adequate in size to
> fit local needs, not squeezing the universal expansion of the network.

Just to add a bit to what Ian said, please note that methods of writing
down arbitrary-length numbers in binary are well-understood and have been
well-understood for quite some time.  Lack of an algorithm is not why
network addresses use fixed-width fields.  Rather, the problem is that
arbitrary-length numbers are much slower because you don't know exactly
how long the packet header is going to be and therefore cannot write
highly-optimized software (generally accompanied by highly-optimized
hardware) for routing packets when you use variable-length packet headers.
The performance penalty would be prohibitive for Internet routers.

This was a topic of considerable discussion during the IPv6 design, since
of course everyone would have preferred to use arbitrary-length addresses
had it been possible.

Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>

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