Bind internal behavior when used as resolver

[Kevin Darcy]

Surya ARBY wrote:
> Hello all.
> I'm making a study about GSLB (Global Site Load Balancing) which is some kind of "advanced" load balancing based on DNS. To be exhaustive and to be sure to understand impacts on clients, I need to know how Bind behaves when used as resolver/caching system. In fact I couldn't find any reliable information on the Net, and the official documentation doesn't describe the internal processing of Bind.
>
> Here are my questions, I hope someone will be able to reply :-)
>   
Frankly, this sounds like a homework assignment, rather than "real 
world" questions.

I may be wrong on that, if so, pardon the rudeness of my responses, but 
the point of studying a subject is to *learn* it, not just copy answers 
from other people.
>
> - By default, does Bind honor the TTL value read in DNS answers ?
>   
Set up a BIND instance and test this.
> - Is it possible to overwrite this TTL value to use another one defined by the local administrator ?
>   
See max-cache-ttl in the documentation.
> - What is the behavior when TTL read is equal to 0 ? Can we be sure it doesn't cache ? 
>   
Set up a BIND instance and test this.
> - Is TTL overwriting often used ?
>   
N/A.
>
>
> About Multiple IP Responses, when Bind sends a query for domain name (for example www.foo.com) and the reply contains multiple IP addresses, how does it behaves ? 
>   
Set up a BIND instance and test this.
> I read that Bind sends to the clients only one IP address took in the pool in a pseudo-random (Round Robin ?) fashion. Is it true ?
>   
Set up a BIND instance and test this.
> Also, is Bind configurable to reply with all IP addresses to the client ? In this case, is the initial order of IP addresses received initially by Bind preserved ? 
See rrset-order in the documentation.

                                                                         
- Kevin