On Fri, 30 June 2023, 04:19 Joel Halpern, <[email protected]>
wrote:

> One of the arguments made in these documents seems to be that by using
> this technology you can reduce latency by skipping the DNS step.
>
> I do not see how that works.  Are you assuming that applications will
> have the anycast address for a given service hard coded?  And that all
> operators providing this service will use the same anycast address for
> the service?  That seems a big ask but unless you do that, DNS is still
> required.


Encoding service or function identifiers has been done in multicast
addresses rather than using DNS to discover them. In IPv6 multicast
addresses there are both well-known IANA and locally defined multicast
group ids in addresses.

One perspective on anycast is that it is similar  to multicast, except that
the packet is being delivered to only 1 of possibility many anycast
destinations, rather than being duplicated if necessary and being delivered
to all of possibility many multicast destinations.

Unicast - 1 to 1
Anycast - 1 to any
Multicast - 1 to many

I came up with the following formal IPv6 anycast addressing scheme a while
back which accommodated both well known and locally defined service or
function identifiers in anycast addresses, heavily inspired by IPv6
multicast's identifier capabilities.

https://datatracker.ietf.org/doc/html/draft-smith-6man-form-func-anycast-addresses

Regards,
Mark.

And that is putting aside the fact that we have found that
> the indirection through DNS and the resultant decoupling is very helpful.
>





> Yours,
>
> Joel
>
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