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@a.mx.aol.com, you want to send mail to user@aol.com. 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@skynet.be> "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, Historical Review of Pennsylvania.