NAME

       dnstcpbench - tool to perform TCP benchmarking of nameservers

SYNOPSIS

       dnstcpbench [OPTION]... REMOTE-ADDRESS [REMOTE-PORT]

DESCRIPTION

       dnstcpbench reads DNS queries (by default from standard input) and sends them out in parallel to a remote
       nameserver.  By  default  TCP/IP  is  used,  but  optionally,  UDP  is  tried first, which allows for the
       benchmarking of TCP/IP fallback.

       The program reports both mean and median numbers for queries per second and UDP  and  TCP  latency.  Each
       query  only counts once, even if it is tried over UDP first. This effectively means that passing '-u' can
       lower query rates if many queries get shunted to TCP.

       The input format is one query per line: qname single-space qtype. An example:

          www.powerdns.com ANY

       When benchmarking extended runs, it may be necessary to enable TIME_WAIT recycling, as TCP/IP port tuples
       may otherwise run out. On Linux this is performed by running:

          echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle

       The equivalent for IPv6 is not known.

OPTIONS

       REMOTE-ADDRESS
              IPv4 or IPv6 to test against.

       REMOTE-PORT
              Port to test against, defaults to 53.

       -f <FILENAME>, --file <FILENAME>
              FILENAME from which to read queries. Defaults to standard input if unspecified.

       -h, --help
              Provide a helpful message.

       --timeout-msec <MSEC>
              MSEC milliseconds to wait for an answer.

       -u, --udp-first
              Attempt resolution via UDP first, only do TCP if truncated answer is received.

       -v, --verbose
              Be wordy on what the program is doing.

       --workers <NUM>
              Use NUM parallel worker threads.

BUGS

       Currently the timeout code does not actually perform non-blocking connects or writes. So a  slow  connect
       or slow writes will still cause low performance and delays.

       Median queries per second statistics are reported as 0 for sub-second runs.

AUTHOR

       PowerDNS.COM BV

COPYRIGHT

       PowerDNS.COM BV

                                                  Aug 22, 2025                                    DNSTCPBENCH(1)