RBL performance: caching nameserver vs RBL mirroring

[Richard Frovarp]

Julian Field wrote:
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> Alex Neuman van der Hans wrote:
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>> Michael Masse wrote:
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>>> Can someone explain the pro's and con's of each with respect to
>>> performance and accuracy, or am I confused and they are not actually
>>> mutually exclusive, and have nothing to do with eachother?
>>>
>>> Mike
>>>
>>>       
>> Caching nameserver means "keep a copy of DNS lookups so I don't have 
>> to do it again for some time". RBL Mirroring means "don't ask a remote 
>> RBL every time I get a message; download the changes to the list 
>> periodically".
>>     
> As a general rule, you don't need your own mirror of an RBL unless you 
> are doing well over 100,000 messages per day. Below that figure, most of 
> the RBL managers won't give you a feed for a mirror anyway. Get a 
> caching nameserver going first (essential) and see how you get on and 
> measure your message throughput. If you are well into 6 or 7 figures, 
> then think about asking the RBL managers for a direct feed. "rbldns" is 
> the best thing to use for big RBLs, not BIND. Run rbldnsd on a different 
> port and just tell BIND to feed requests for the domain to the port used 
> by rbldnsd.
>   

You want to be running a caching nameserver no matter what. I know a 
certain server that was running MailScanner and for some reason the 
caching nameserver failed on it. It had to make a trip all the way to 
the local DNS (same room), and it got very very very backed up. Of 
course this is a server that probably handles a 100,000 alone on a light 
day. No wonder the end-to-end monitor kept paging all weekend.