Examples:

   1  2
   3 13 TCP/SMTP/mail
   1 21 Postel@F.ISI.USC.ARPA

   1  2
   3 13 TCP/NIFTP/RFT
   1 12 TSC.SRI.ARPA

     The first example is a resolution request for the name
"Postel@F.ISI.USC.ARPA".  It is 21 octets in length.  The requested
application service is TCP/SMTP/mail.  The second example is a
resolution request for application service NIFTP at TSC.SRI.ARPA.


                                   8
 
RFC 830                                                       October 1982



AFFIRMATIVE RESPONSE

   Command Type   Number of Items

   Service Indicator   Length   Transport Protocol/Service/Service Type

   Name Indicator   Name Length    Name String

   Address Indicator   Address Length   Address

Examples:

   2  3
   3 13 TCP/SMTP/mail
   1 21 Postel@F.ISI.USC.ARPA
   2  6 "10  2  0 52  6 25"

   2  4
   3 13 TCP/NIFTP/RFT
   1 12 TSC.SRI.ARPA
   2  6 "10  3  0  2  6 47"
   2  6 "39  0  0  5  6 47"

     An affirmative response implies that the destination offers the
requested service.  The parsing of an address is implied by the
indicated transport protocol.  In the first example, the transport
protocol is TCP.  Thus, the address is composed of three fields: the
internet address ("10 2 0 52"), the protocol number ("6" for TCP [3]),
and the port number ("25" for SMTP [3]).  A multiple-address response in
the second example indicates that TSC is multi-homed via both ARPANET
(net  10), and SRINET (net  39).  A multiple-resolution response is
preferred.  It offers the source a choice.

NEGATIVE RESPONSE

   Command Type   Number of Items

   Service Indicator   Length   Transport Protocol/Service/Service Type

   Name Indicator   Name Length   Name String

   Name Indicator   Name Length   Partial Name String

   [Comment Indicator   Comment Length   Comment]

     This indicates difficulty in resolution.  Returned with this
command is the left-most portion of the specified name including the
difficulty encountered.  An optional comment item may be included.




                                   9
 
RFC 830                                                       October 1982


Examples:

   3  4
   3 13 TCP/SMTP/mail
   1 16 Postel@F.ISI.USC
   1 16 Postel@F.ISI.USC
   9 18 Resolution Failure

   3  4
   3 13 TCP/NIFTP/RFT
   1 13 TSC..SRI.ARPA
   1  5 TSC..
   9 17 Syntactic Anomaly

In the first example, the resolution failed because USC is not top-level
domain.  The syntactic error of adajacent dots in the second example is
obvious.

INCOMPATIBLE SERVICE