8. Fictional example

   This is (part of) the zone file for asdf.com, a still-unused domain:

        $ORIGIN asdf.com.
        @               SOA server.asdf.com. root.asdf.com. (
                            1995032001 3600 3600 604800 86400 )
                        NS  server.asdf.com.
                        NS  ns1.ip-provider.net.
                        NS  ns2.ip-provider.net.
        ftp.tcp         SRV 0 0 21 server.asdf.com.
        finger.tcp      SRV 0 0 79 server.asdf.com.
        ; telnet - use old-slow-box or new-fast-box if either is
        ; available, make three quarters of the logins go to
        ; new-fast-box.
        telnet.tcp      SRV 0 1 23 old-slow-box.asdf.com.

                        SRV 0 3 23 new-fast-box.asdf.com.
        ; if neither old-slow-box or new-fast-box is up, switch to
        ; using the sysdmin's box and the server
                        SRV 1 0 23 sysadmins-box.asdf.com.
                        SRV 1 0 23 server.asdf.com.
        ; HTTP - server is the main server, new-fast-box is the backup
        ; (On new-fast-box, the HTTP daemon runs on port 8000)
        http.tcp        SRV 0 0 80 server.asdf.com.
                        SRV 10 0 8000 new-fast-box.asdf.com.
        ; since we want to support both http://asdf.com/ and
        ; http://www.asdf.com/ we need the next two RRs as well
        http.tcp.www    SRV 0 0 80 server.asdf.com.
                        SRV 10 0 8000 new-fast-box.asdf.com.
        ; SMTP - mail goes to the server, and to the IP provider if
        ; the net is down
        smtp.tcp        SRV 0 0 25 server.asdf.com.
                        SRV 1 0 25 mailhost.ip-provider.net.
        @               MX  0 server.asdf.com.
                        MX  1 mailhost.ip-provider.net.
        ; NNTP - use the IP providers's NNTP server
        nntp.tcp        SRV 0 0 119 nntphost.ip-provider.net.
        ; IDB is an locally defined protocol
        idb.tcp         SRV  0 0 2025 new-fast-box.asdf.com.
        ; addresses
        server          A   172.30.79.10
        old-slow-box    A   172.30.79.11
        sysadmins-box   A   172.30.79.12
        new-fast-box    A   172.30.79.13
        ; backup A records - new-fast-box and old-slow-box are
        ; included, naturally, and server is too, but might go
        ; if the load got too bad
        @               A   172.30.79.10
                        A   172.30.79.11
                        A   172.30.79.13
        ; backup A RR for www.asdf.com
        www             A       172.30.79.10
        ; NO other services are supported
        *.tcp           SRV  0 0 0 .
        *.udp           SRV  0 0 0 .

   In this example, a telnet connection to "asdf.com." needs an SRV
   lookup of "telnet.tcp.asdf.com." and possibly A lookups of "new-
   fast-box.asdf.com." and/or the other hosts named.  The size of the
   SRV reply is approximately 365 bytes:

      30 bytes general overhead
      20 bytes for the query string, "telnet.tcp.asdf.com."
      130 bytes for 4 SRV RR's, 20 bytes each plus the lengths of "new-

        fast-box", "old-slow-box", "server" and "sysadmins-box" -
        "asdf.com" in the query section is quoted here and doesn't
        need to be counted again.
      75 bytes for 3 NS RRs, 15 bytes each plus the lengths of
        "server", "ns1.ip-provider.net." and "ns2" - again, "ip-
        provider.net." is quoted and only needs to be counted once.
      120 bytes for the 6 A RR's mentioned by the SRV and NS RR's.