In einer eMail vom 21.04.2009 23:54:19 Westeuropäische Normalzeit schreibt
bill at herrin.us:
On Tue,
Apr 21, 2009 at 4:00 AM, <HeinerHummel at aol.com> wrote:
> As
I understand Anycast is about delivery to one out of multiple
>
destinations within a given scope.
Hi Heiner,
I would have said
"closest one from the set of valid destinations,"
but your version is good
enough.
More precisely "closest one from the set of valid destinations with respect
to the source,"
> Where is the center point of this scope ? Is it always
the location of the
> source ?
I don't understand the question.
What is a center point wrt routing?
My question is: with anycast do we always understand the above, or could it
also be any particular destination within the scope of an indicated remote
location like a different continent?
What do we understand by Anycast in the future ? Some one must do the
mapping to a specific Unicast address? Is it always the ingress ? Or can't there
be reasonable anycast services which require to send the data to some far
distant anycast server where it will be mapped to some local unicast
addresss ?
>
What are the requirements for Anycast in a new architecture?
Well,
that's the crux of the discussion, isn't it? Anycast and unicast
are
identical in every respect in the current architecture. How do we
bound the
unforeseeable consequences if that isn't true in the new
one?
I'm
getting ready to introduce an anycast route into the table in
order to
implement a "continuing operations" system with three sites
half a world
apart. "Continuing operations" is a fancy phrase for
"disaster recovery,"
something that became really popular almost 8
years ago. Once a packet hits
any of the always-running sites, a VPN
takes it back to the site with the
servers flagged "best" for that
particular address, so holistically its
unicast but from the
perspective of the Internet core its anycast from
three distinct
locations.
Would this have any hope of working right
in an architecture that
didn't accommodate anycast? How many such uses are
out there, ready to
impede the deployment of the unwary
plan?
Sorry, I don't understand what you are hereby saying.
Heiner
Regards,
Bill Herrin