Minimize DNS Lookups


For viewing all tips see here

Applicable To
All Browsers

How Improves Page Load Time
o        By optimizing network latency

Prologue
Before a browser can establish a network connection to a web server, it must resolve the DNS name of the web server to IP address.  If the DNS resolution has already been performed then it can be resolved from Browser / OS cache else it needs to be looked over the network using DNS server(s)

Why
o        To minimize time taken during DNS name resolution
o        Reusing domains allows the browser to reuse TCP connections more frequently, further reducing the network time

How
o        Use URL paths instead of host names wherever possible.  For example, instead of hosting developer site on developer.rootDomain.com, host it on www.rootDomain.com/developer

Exceptions
o        There are benefits also from using multiple hostnames to induce parallel downloads.  See Tip {TODO}.

Recommendations
o        Between 1 and 5 hosts, where 1 main host and rest of the hosts (not counting external hosts, such as ads) for parallelizing static resources like images, java scripts, style sheets etc.
o        Shouldn't use more than one host for fewer than 6 resources and fewer than 2 resources on single host is especially wasteful

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