Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!CS.WISC.EDU!hagens
From: hagens@CS.WISC.EDU
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Re: Proposal for use of DNS to store RFC 987, etc mappings
Message-ID: <9007181728.AA00340@janeb.cs.wisc.edu>
Date: 18 Jul 90 16:28:55 GMT
References: <1217.648201567@UK.AC.UCL.CS>
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: inet
Organization: The Internet
Lines: 51


> 5.0 "This implies that there will be two separate copies of the 
> mapping database, one in table form, and the other within the internet
> DNS Namespace".     I agree that this is the case.  If we go down this
> path, it is imperative that we have solid mechanisms to keep these
> two views consistent.   I don't think that you have really addressed this.

No, your right. We did not discuss the specifics for keeping the 
authoritative data for a specific DNS server
and the table form consistent. At one level, it is
simply a program that produces one form from the other. At a higher level,
there are issues concerning the way in which the US collects its tables and
disseminates them to the rest of the world (and vice versa). 
Another issue is how to deal with inconsistencies that may result if a site
changes their DNS server configuration file before the change has been
propagated to those gateways which do not have DNS access.

In general tho, do you think the coordination of the tables and
server config files is feasible?

> 
> I think that the preference value is an interesting idea, however I 
> don't see why it is really needed.  Then 987 mappings are global.   There
> should be no need to have alternate/preferred mappings.   A preference
> mapping would be more appopriate when choosing a 987 gateway, but not
> for the base 987 mapping.   

In retrospect, I think the preference field is not going to work, for reasons
you site above. I think that in the 822->X.400 direction, the preference
field of MX records can be used to find the gateway. In the other direction,
it is a matter for X.400 routing to solve.

> 
> You may use 987 mappings to reformat a header containing a large number of
> addresses.   It would seem reasonable to reformat the header in a single 
> process.   There might be problems with DNS timeouts for headers
> with a very large number of addresses.   

Yes, this is a problem with the DNS today with RFC 822 mail!
We need to make sure that back-up servers are distributed correctly.
Of course, running the DNS over the OSI connection-less network will
drastically improve connectivity and dependability! :^)

> Overall, I have a lot of sympathy with the approach you propose.  The format
> of Appendix F of 987 was not a co-incidence.   However, I have a lot of
> concern that it is not the correct operational choice.
Could you elaborate here? 

Thanks,

Rob