Re: Generic anycast addresses...

[Mark Smith <[e-mail]>]

On Fri., 31 May 2019, 09:37 Ted Lemon, <[e-mail]> wrote:

> On May 30, 2019, at 4:21 PM, Mark Smith <[e-mail]> wrote:
>
> An example use case for a Network Service Provider scope is anycast DNS
> resolvers.
>
>
> And how does this work if you are multihomed?
>
>

Other email I just sent.

Adding, even if both upsream/parent NSPs are providing DNS resolver service
with the same NSP scoped anycast address (because it will be a generic NSP
scoped DNS resolver address), the downstream customers' routing will pick
only one of them to use.

Similar to multicast, what I've proposed supports embedding a unicast /64
prefix. The all-zeros /64 is used as "unspecified".

So in this scenario, both NSPs would advertising the same generic NSP
scoped anycast DNS resolver address with an all zeros /64 part - and likely
such a well-known anycast address that it could be a factory default for
devices. They may also each advertise an NSP scoped anycast DNS address
which embeds one of their GUA /64s.

So a customer could leave the choice of which NSP's DNS resolver they use
entirely up to their routing system by using the generic DNS anycast
address, which would be the default, or they could prefer only one of their
NSP's DNS anycast resolver services by configuring their hosts to use that
NSP's specific anycast DNS address that includes the NSP's chosen GUA /64.

They could go further and configure the second NSP's specific NSP scope
anycast DNS resolver address as a second DNS entry on a host to get NSP
independent DNS redundancy, if the first and preferred NSP's DNS anycast
resolution service isn't considered reliable enough.

Regards,
Mark.



>