[SURBL-Discuss] Combined SURBL A record format (Was: Re: Bill
Stearns' sa-blacklistavailable as SURBL: ws.surbl.org)
Scott at ncs.co.nz
Wed Apr 21 21:29:27 CEST 2004
> Good to know. Sounds like it's mostly a question of style
> then, though multiple A records would require no new coding
> whereas bitmasks would.
> > Using the DNSBL
> > Anyone can query our DNSBL through normal DNS means. Just
> > reverse the octets and do a name lookup. For example, to check
> > if 127.0.0.2 is present in opm.blitzed.org, do a DNS lookup on
> > 126.96.36.199.opm.blitzed.org. Each entry in the DNSBL has an A
> > record and a TXT record associated with it, the TXT record
> > contains a URL to the proxy information page specific to that
> > IP address telling the user a little information about how to
> > sort out the proxy.
> > In opm.blitzed.org, the A record has an IP address of 127.1.0.x
> > where x is a bitmask of the types of proxy that have been
> > reported to be running on the host. The values of the bitmask
> > are as follows:
> > WinGate 1
> > SOCKS 2
> > HTTP CONNECT 4
> > Router 8
> > HTTP POST 16
> The bitmask approach is more compact, but the multiple A record
> approach is more human-readable and transparent IMO. I'm leaning
> towards the latter, but am interested in any other comments.
> Jeff C.
This is all quite interesting.
I'm happy with either method obviously. Excuse my ignorance with regards to DNS lookups, but do all the A records come down with the first DNS lookup, or are they fetched each time from the remote server?
What are the traffic overheads with incorporating either type of method - I would have thought that the bit mask method would cause less traffic - also with smaller zone transfers?
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