RIS anchor/beacon changes

Dear all,

In the coming months we will be making several changes in the prefix 
advertisements by RIS Route Collectors. These changes were discussed 
previously on RIPE Labs[0].

January 2nd 2024
----------------
The following BGP announcements will be disabled:

   * IPv4 anchor+beacon announcements on RRC04, RRC07, RRC10, RRC13, 
RRC14, RRC15, RRC16, RRC21 and RRC22
   * IPv4 anycast failover simulation beacon (84.205.72.0/24) on RRC03 
and RRC14

All IPv6 anchor+beacon announcements will remain.

February 1st 2024
-----------------
We will be enabling the following new prefix advertisements:

   * A single anycast IPv4 and IPv6 anchor+beacon pair per RIR region, 
advertised from each RRC in this region.
   * An anycast IPv4 /25 and /28 anchor, advertised from one RRC per RIR 
region
   * An anycast IPv6 /56 and /64 anchor, advertised from one RRC per RIR 
region

To accommodate these changes we will also modify the encoding used in 
the BGP AGGREGATOR attribute.

For full details and an overview of all anchor and beacon prefixes, 
please refer to our updated documentation[1].

Kind regards,
Martin Pels
RIPE NCC

[0] 
https://labs.ripe.net/author/emileaben/ris-beaconing-shining-a-light-on-bgp-dynamics/
[1] https://ris.ripe.net/docs/routing-beacons