Re: Reason for Limited number of Root DNS Servers

Aleksander Kurczyk aleksanderkurczyk at
Fri Nov 11 13:43:40 UTC 2011

There is more than 13 physical root servers but these servers have only 13 domain names ( and ip addresses. Only 13 because of limitation of single DNS message to 512 bits (RFC 1035). -- List and map of the root servers
Dnia 11 listopada 2011 6:38 Gaurav Kansal <gaurav.kansal at> napisał(a):
Dear All,
Somewhere I read that number of ROOT DNS servers is limited to 13 because of protocol limitation of DNS and UDP.
Exact writing was  “A combination of limits in the DNS and certain protocols, namely the practical size of unfragmented User Datagram Protocol (UDP) packets, resulted in a limited number of root server addresses that can be accommodated in DNS name query responses. This limit has determined the number of name server installations at (currently) 13 clusters, serving the needs of the entire public Internet worldwide.”
As root DNS are running in anycast so number is not an issue at all. But I don’t understand where exactly is this limitation exists???
Please some elaborate on this.
Thanks and Regards,
Gaurav Kansal
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Aleksander Kurczyk
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