Any one knows what id's full meaning?

[Robert Wessel]

Larry Liu <Larry.Liu at lagrace.org> wrote in message news:<bor8i1$1bbe$1 at sf1.isc.org>...
> Below is a nslookup result with "set debug".  Does anyone have a full 
> understanding  for id=15 in line 3 ?  Is the the 15th query from a 
> particular client before the ttl, expiration day, or otherwise?  Thanks.
> 
> ------------
> Got answer:
>     HEADER:
>         opcode = QUERY, id = 15, rcode = NOERROR
>         header flags:  response, want recursion, recursion avail.
>         questions = 1,  answers = 0,  authority records = 1,  additional = 0
> 
>     QUESTIONS:
>         cnf.com, type = A, class = IN
>     AUTHORITY RECORDS:
>     ->  cnf.com
>         ttl = 7200 (2 hours)
>         primary name server = dmrqs004.cnf.com
>         responsible mail addr = dns_id.dmrqs004.cnf.com
>         serial  = 2003110400
>         refresh = 3600 (1 hour)
>         retry   = 1800 (30 mins)
>         expire  = 604800 (7 days)
>         default TTL = 7200 (2 hours)
> 
> ------------
> Name:    cnf.com


The client sets an arbitrary ID in each DNS query it sends.  The
server copies that ID into the reply.  If the client has more than one
query outstanding (especially to the same server), it can use the ID
to match the response to a particular request.  Frankly it ought to do
that in any case to help avoid cache poisoning.