Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!tut.cis.ohio-state.edu!ucbvax!YKTVMZ.BITNET!ELINSKY
From: ELINSKY@YKTVMZ.BITNET ("Jay Elinsky")
Newsgroups: comp.protocols.tcp-ip
Subject: Resolver implementation
Message-ID: <9001160443.AA25802@ucbvax.Berkeley.EDU>
Date: 16 Jan 90 02:49:24 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 55

I'm posting this for someone who has read-only access to this list.  He
asks that you post comments to the list.

 I know of two different methods for implementing a resolver, which are
 described below.  I'd like to hear comments on which is preferred
 because of usability, and any problems with either of the schemes.

 Both require a RESOLV.CONF file that contain the standard DOMAIN
 statement and NAMESERVER statements.

 Example:  DOMAIN WATSON.IBM.COM
           NAMESERVER X.X.X.X

 Method I
 --------
 If the host name does not contain a period, append the domain name
 before sending the name to the resolver.

 Example:  PING YORKTOWN  sends  YORKTOWN.WATSON.IBM.COM  to the resolver.
           PING YORKTOWN.WATSON sends YORKTOWN.WATSON to the resolver.

 Advantages:  Simple to implement, simple to understand, only one
              query is ever sent to the name server.

 Method II
 ---------
 Always append the domain name, and gradually remove the first element
 in the DOMAIN statement trying all possibilities.

 Example:  PING YORKTOWN.WATSON.IBM.COM
 would send to the resolver:   YORKTOWN.WATSON.IBM.COM.WATSON.IBM.COM
                       then:   YORKTOWN.WATSON.IBM.COM.IBM.COM
                       then:   YORKTOWN.WATSON.IBM.COM.COM
                       then:   YORKTOWN.WATSON.IBM.COM  (success)
           PING YORKTOWN.WATSON
 would send to the resolver:   YORKTOWN.WATSON.WATSON.IBM.COM
                       then:   YORKTOWN.WATSON.IBM.COM  (success)

 Advantages:  A user could specify part of his domain (like
              YORKTOWN.WATSON), provided that part was in their domain
              tree.

 Disadvantages:  Complicated, the Hosts Requirements RFC says that if
                 this method is implemented that a method must be provided
                 to turn it off, and that all negative queries must be
                 cached to prevent further negative traffic to the DNS.


 Has anybody successfully implemented Method II?  And if so, what kind
 of user feedback have you gotten?

 Daniel M. Barton
 TCP/IP Development
 IBM Corporation
 Research Triangle Park, NC