Re: Draft on using SRV records to locate whois servers

[Brad Knowles <]

At 3:18 PM +0100 2002/05/01, James Raftery wrote:

>  Firstly, this draft appears to use different semantics for the domain
>  name of an SRV RR than those in RFC2782. My reading of 2782 is that the
>  ``name'' portion of the RR owner (i.e. the name component of
>  _service._protocol.name) is analogous to the server name the client
>  wants to contact.
>
>  Without SRV records, if I wish to use whois to talk to a server named
>  whois.isp.net I should lookup the A record of whois.isp.net and
>  contact that host.
>
>  With SRV I should lookup the SRV of _whois._tcp.whois.isp.net and
>  contact the host specified by the A record owned by the SRV target.
	Not correct.  Think about mail and the MX record.  You don't want 
to send mail to user@localhost, you want to send mail to 
user@localhost.  So, you look up the MX records for aol.com.

	Likewise for whois.  You don't want the whois information for the 
server whois.domain.example, you want the whois information for 
domain.example itself, which is a different question.  You only fall 
back to using whois.domain.example in the case where no SRV record 
exists for the whois service.

>  2782 says if you want to contact host foo for service X over protocol Y,
>  then lookup "_X._Y.foo IN SRV".
	Correct.

>                                   This draft says if you want to send a
>  query ABOUT foo to a whois server, lookup "_whois._tcp.foo IN SRV".
	Correct.  Note that this is not "_whois._tcp.whois.foo IN SRV".

>                                                                       The
>  semantic meaning of ``foo'' has changed and that change is not explicitly
>  stated. I would like it to be.
	I believe that you have misunderstood, or at least you are not 
sufficiently explaining exactly where in the draft you are seeing 
this apparent change.

>  Secondly, I feel a reminder that the target of an SRV must have an A RR
>  is in order. Taking my isp.net example, above, again. If I controlled
>  customer.com and wanted to use the mechanism in this draft to publish
>  the fact that customer.com is in isp.net's whois server I cannot use:
>
>  _whois._tcp.customer.com.	IN	SRV	10 0 43 whois.isp.net.
>
>  as ``whois.isp.net'' does not have an A RR.
	No, you wouldn't provide the glue for it in your zone, but the 
owner may very well have an A record defined somewhere else, 
presumably within the isp.net zone.

>                                               I must ``undo'' the
>  name indirection desired by isp.net and instead publish the following
>  RRs (and keep them up to date):
>
>  _whois._tcp.customer.com.	IN	SRV	10 0 43 dbserver.isp.net.
>  				IN	SRV	20 0 43 dbbackup.isp.net.
	I don't see how the RHS of this example is any different from the 
RHS of the example given above.  Who says that whois.isp.net is not a 
perfectly valid host/domain name, which resolves to an A record, 
possibly among a whole host of other things?

--
Brad Knowles, <brad.knowles@localhost

"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
    -Benjamin Franklin, Historical Review of Pennsylvania.