Smaller than a /24 for BGP?

William Herrin bill at
Sun Jan 29 06:17:07 UTC 2023

On Sat, Jan 28, 2023 at 5:48 PM Masataka Ohta
<mohta at> wrote:
> The following way in my ID:
>     The easiest way for applications know all the addresses of the
>     destination is to use DNS. With DNS reverse, followed by forward,
>     lookup, applications can get a list of all the addresses of the
>     destination from an address of the destination.

The DNS provides no such guarantee. Moreover, the DNS does guarantee
its information to be correct until the TTL expires, making it
unsuitable for communicating address information which may change

> As for (long lasting) TCP, my ID says:
>     With TCP, applications must be able to pass multiple addresses to
>     transport layer (e.g. BSD socket).
> which implies addresses are supplied from applications by
> DNS look up.

Which is a bit of hand-waving since the protocol can't do anything
with that information regardless of whether you expand the API to
provide it. Even if it could, you  also miss the point that the
information -may change- during the ongoing connection so you can't
just statically retrieve it.

Bill Herrin

For hire.

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