What algorithms do DNS servers use for faster searches?

Question

DNS servers must be fast to avoid latency. What algorithms do DNS servers use to reduce latency? Are they some kind of caching mechanisms that can be effectively used to increase speed?

Answer 1

Delay is a huge problem with DNS. The slowest part of the DNS spreads over the network and requests other servers. Any client or server caching will speed up the process. In fact, this is exactly what is happening.

When the DNS server responds to the query, the response is returned with TTL (lifetime). The TTL value tells the request server how long to cache the response. The TTL value is set by the authoritative server for the zone. This is usually about one day, but may vary depending on how often the administrator thinks that the DNS record may change.

The DNS client (which may be another server acting on behalf of the end user) caches the response and dumps it from its cache when TTL is exceeded. Until this time, subsequent requests for this particular host name will exit the cache.

I used my own DNS server at home, so all my computers on the local network could use the local cache. But I found that it is better to use ISP DNS servers. They took advantage of the requests of thousands of clients and were much more likely to get more cached responses than my servers could ever have.

Answer 2

I know this question already has an accepted answer, but much more you can do than just caching. For example:

• Use BGP to create a network of geographically distributed servers accessible through Anycast. This can reduce the average number of hops that a DNS query packet must go through.

• Eliminate the infrastructure containing the delay. For example, host your DNS servers at your ISP or at a large access point on the Internet, and not at the slow end of the global network.

• Avoid CNAME records; instead, A. A. CNAME records often require the resolution of several queries.

• Use a reliable, high-performance commercial service such as UltraDNS.