IP Assignments for Anycasting DNS
1. PROS & CONS
A.1 Acceptance of DNS for Special Treatment
Studies show clearly that ccTLD and gTLD name servers are a critical network infrastructure that justify special policies to guarantee operability of Internet applications.
A.2. Policy Harmonisation
Three out of five RIRs (APNIC, ARIN and LACNIC) have policies allowing assignments to network critical infrastructure. All three policies classify TLD name servers as critical infrastructure. Extracts from these policies can be found in Appendices I through III.
A.3 Scalability of DNS
To serve the projected increase of DNS queries and to ensure sufficient network topological coverage and diversity TLD managers need to deploy
an increasing number of name servers.
Internet has become part of the daily life and their availabilty is as important as the availability of all public services. Anycasting is currently the state-of-the-art solution to lower the impact of Distributed Denial of Service (DDoS) attacks.
A.5 IPv6 Support
As the world starts exploiting IPv6, the DNS infrastructure should support IPv6 natively. However it is not yet possible to reduce the number of name servers in the IPv4 cloud.
B.1 Waste of Address Space
Accepting a number of IPv4/24 and IPv6/32 allocations for critical network infrastructures does not align with the traditional address conservation efforts. With anycasting it is very likely that only a few addresses from the entire assignment would be used.
B.2 Root DNS are Special, Others are Not
RIPE Document 233 dated 24 May 2002 says: "Although it is undesirable to give special status to any IP (IPv4 or IPv6) address block, it was agreed by the community that the particular need defined in this document is the only justifiable exception to that general principle."
Assigning an own network prefix is just a workaround to ensure global reachability which could also be achieved by adjusting currently deployed route filter practices.