Re: Shared cache servers on an island's IXP

[Stephane Bortzmeyer <bortzmeyer () nic fr>]

On Thu, Jan 18, 2024 at 12:53:19PM +0100,
 Jérôme Nicolle <jerome () ceriz fr> wrote 
 a message of 36 lines which said:

> - Low redundancy of old cables (2)
> - Total service loss when both cables are down because of congestion on
> satelite backups

A problem which is not often mentioned is that most (all?) "local
caches" (CDN, DNS resolvers, etc) do not have an "offline mode" (or
"disconnected-from-master mode"). During an outage, they continue to
work for some time then break suddenly, in a not-friendly way, serving
various error messages instead of old data and/or useful
messages. (For instance, the DNS resolver may not be able to serve
stale answers.)

The time during which they can continue to work when they are
disconnected from their master is typically undocumented (except for
the DNS), and discovered only when there is a long outage.

Making the Internet work better with sometimes-broken connectivity is
still an area of research.