Resolver – SWITCH Security-Blog

SWITCH operates recursive name servers for any user within the Swiss NREN. While larger universities typically run their own recursive name server, many smaller organisations rely on our resolvers for domain name resolution. During the consolidation of our name server nodes into two data centres, we looked for opportunities to improve our setup. Dnsdist is a DNS, DoS and abuse-aware load balancer from the makers of PowerDNS and plays a big part in our new setup. While the first stable release of dnsdist (version 1.0.0) is only a few days old (21 April 2016), it feels like everyone is already using it. We are happy users as well and want to share with you some of the features we especially like about dnsdist.

Our old setup consisted of several name server nodes which all shared the same IP address provided by anycast routing. Our recursive name server of choice was and still is BIND, and we have been providing DNSSEC validation and malicious domain lookup protection through our DNSfirewall service for some time. While this setup worked very well, it had the disadvantage that some badly behaved or excessive clients could degrade the performance of a single name server node and as such affect all users routed to this node. Another disadvantage was that each name server node got its share of the whole traffic. While this may sound good, it has the disadvantage that we have several smaller caches, one on each node. My favorite quote from Bert Hubert, founder of PowerDNS, is: “A busy name server is a happy name server“. What it means is that it is actually faster to route all your queries to a single name server node because this will improve the cache-hit rate.

Dnsdist provides a rich set of DNS-specific features
Our new setup still makes use of anycast routing. However, it is now the dnsdist load balancer nodes that announce this IP address, and they forward the queries to the back-end recursive name servers for domain name resolution.

The server nodes are located in two data centres, and both load-balancers announce the same IP address to make use of anycast routing. Query load is typically sent to resolvers within the same data centre but is distributed to the other site as well in the event of a higher load or server loss.

Das Domain Name System (DNS) ist ein wichtiger Bestandteil des Internets. Aus Endbenutzersicht erscheint das Internet oft zusammengebrochen, wenn die Namensauflösung nicht funktioniert. In den letzten Jahren wurden Schwachstellen im Protokoll aufgedeckt, welche es erlauben, DNS-Antworten für einen DNS-Resolver zu manipulieren. Um die Vertrauenswürdigkeit der Daten sicherzustellen, wurde die Erweiterung DNSSEC entwickelt.

Was ist DNSSEC?

DNSSEC ist eine Erweiterung des Domain Namen Systems (DNS), die dazu dient, die Echtheit (Authentizität) und die Vollständigkeit (Integrität) der Daten von DNS-Antworten sicherzustellen.

Continue reading “DNSSEC – Einführung zu DNS Security Extensions”