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The attack launched in February 2007 against the domain name service (DNS) root servers targeted six servers but only significantly affected two of the systems,
according to a report issued by the Internet Corporation for Assigned Names and Number (ICANN).
Six of the 13 root servers that
form the foundation of the Internet were affected; two badly. The two worst affected were those that do not have
new Anycast technology installed.
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| What is Anycast?
On the Internet, anycast is usually implemented by using BGP to simultaneously
announce the same destination IP address range from many different places on the Internet. This results in packets addressed to destination addresses in this range being routed to the "nearest" point on the net announcing the given destination IP address.
For a DNS root servers, anycast provides a service where by clients send requests to the service address and the network delivers that request to at least one, preferably the closest, instance in the root server�s anycastgroup.
The Anycast scheme has two major benefits:
- servers automatically spread the impact of an attack amongst themselves
- no local disaster can disrupt the operation of the root server as a whole
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DNS root server and Anycast
A root name server is a DNS server that answers requests for the root namespace domain, and redirects requests for a particular top-level domain (TLD) to that TLD's nameservers.
The term "root name server" is generally used to describe the thirteen well-known root name servers that implement the root namespace domain for the Internet's official global implementation of the DNS.
The root servers hold the list of addresses for the authoritative servers for the top-level domains. Every name lookup must either start with an access to a root server, or use information that was once obtained from a root server.
Once the address of a single functioning root server is known, the rest of the DNS information can be discovered recursively, and the address of any machine on the Internet can be looked up in this way.
An additional level of redundancy is provided by the fact that a single root server name, and its corresponding IP address, may correspond with many physical servers around the world, using a method called Anycast.
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