Need of caching on bind server

[Barry Margolin]

In article <mailman.43.1472100432.74444.bind-users at lists.isc.org>,
 Harshith Mulky <harshith.mulky at outlook.com> wrote:

> I am trying to understand why caching is required on the bind server, when 
> the client receiving the responses would be caching based on TTL values.

A typical caching server has multiple clients. If they're an ISP, it 
will have thousands of clients, and public DNS servers like OpenDNS and 
Google DNS it may have hundreds of thousands. So even if the clients 
have caches of their own (which many do not), the cache is useful so 
that when different clients look up the same name they can be returned 
from cache.

For example, consider all the thousands of lookups for things like 
google.com, twitter.com, etc. that an ISP receives every second. If they 
didn't cache these responses, DNS traffic might rival YouTube (OK, 
that's an exaggeration).

-- 
Barry Margolin
Arlington, MA