Subject: Proposed modification to mDNS-06 draft

From: Bernard Aboba <[email-masked]>
Date: Mon, 29 Oct 2001 19:31:02 -0800 (PST)

Proposer: Erik Guttman 
Date: 10/28/01
Section affected: 3
Rationale: 

The proposed change allows us to completely avoid use of ".local.arpa",
aliasing, etc. Note that this suggestion *does* change the search order
behavior, by  adding a new rule to just try the name.  But section 3 of
mdns-06 also changes the rules, by requiring the adding of local.arpa
suffixes to the search order.
    
Proposal: 

Replace section 3 text:

"
    Multicast DNS usage is determined by special treatment of the
    ".local.arpa."  namespace. The sender treats queries for ".local.arpa."
    as a special case.  A sender MUST NOT send a unicast query for names
    ending with the ".local.arpa." suffix except when:
 
      a. A sender repeats a query after it received a response
         to the previous multicast query with the TC bit set, or
 
      b. The sender's cache contains an NS resource record that enables
         the sender to send a query directly to the hosts
         authoritative for the name in the query.
  
    It is not expected that a host named "host.example.com." will be
    manually configured to have the additional name
    "host.example.com.local.arpa." when it is configured to use multicast
    DNS. Instead, a responder with a name "host.example.com." configured
    with ".local.arpa." suffix in its domain search configuration is
    authoritative for the name "host.example.com.local.arpa.". For example,
    when a responder with the name "host.example.com." receives an A type
    query for the name "host.example.com.local.arpa." it authoritatively
    responds to the query.
 
    The same host MAY use multicast DNS queries for the resolution of names
    ending with ".local.arpa.", and unicast DNS queries for resolution of
    all other names. When a user or application requests a DNS client to
    resolve a dot-terminated name that contains a ".local.arpa" suffix, the
    query for such a name MUST be multicast and the name SHOULD NOT be
    concatenated with any suffix."
 
with the following text:
 
   A mDNS "sender" MAY multicast requests for any name.  If that name
   is not qualified and does not end in a trailing dot, for the purposes
   of mDNS, the implicit search order is as follows:
 
      A. Request the name with the current domain appended. 
      B. Request just the name.
 
   This is the behavior suggested by [21].  mDNS uses this technique 
   resolve unqualified host names.  

[21] Kumar, A., et. al. "DNS Implementation Errors and Suggested
      Fixes", RFC 1536, October 1993.
 
Recommendation: Discuss

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