Editing Load balancing (computing) (section)

====DNS delegation====

Another more effective technique for load-balancing using DNS is to delegate {{mono|www.example.org}} as a sub-domain whose zone is served by each of the same servers that are serving the website. This technique works particularly well where individual servers are spread geographically on the Internet. For example:
:one.example.org A 192.0.2.1
:two.example.org A 203.0.113.2
:www.example.org NS one.example.org
:www.example.org NS two.example.org

However, the zone file for {{mono|www.example.org}} on each server is different such that each server resolves its own IP Address as the A-record.<ref>{{Cite web|url=https://www.zytrax.com/books/dns/ch8/a.html|title=Chapter 8 - IPv4 Address (A) Record|website=www.zytrax.com}}</ref> On server ''one'' the zone file for {{mono|www.example.org}} reports:
:@ in a 192.0.2.1

On server ''two'' the same zone file contains:
:@ in a 203.0.113.2

This way, when a server is down, its DNS will not respond and the web service does not receive any traffic. If the line to one server is congested, the unreliability of DNS ensures less HTTP traffic reaches that server. Furthermore, the quickest DNS response to the resolver is nearly always the one from the network's closest server, ensuring geo-sensitive load-balancing {{Citation needed|date=November 2014}}. A short [[Time to live|TTL]] on the A-record helps to ensure traffic is quickly diverted when a server goes down. Consideration must be given to the possibility that this technique may cause individual clients to switch between individual servers in mid-session.