The Internet is a large and complex aggregation of network
    hardware, connected together by gateways. The traceroute command
    tracks the route packets follow from gateway to gateway. The
    command uses the IP protocol `time to live' field and attempts to
    elicit an ICMP "time exceeded" response from each gateway along
    the path to a particular host.

    The only mandatory parameter is the destination host name or IP
    number. The default probe datagram length is 38 bytes, but you
    can increase this by specifying a packet size (in bytes) after
    the destination host name. This is useful when the -f option is
    given for MTU discovery along the route. You should start with
    the maximum packet size for your own network interface (if the
    given value is even bigger, traceroute attempts to select a more
    appropriate value). If no packet size is given when using the -f
    option, traceroute determines the initial MTU automatically.

    To track the route of an IP packet, traceroute launches UDP probe
    packets with a small ttl (time to live) and then listens for an
    ICMP "time exceeded" reply from a gateway. Probes start with
    a ttl of one and increase by one until either an ICMP "port
    unreachable" is returned (indicating that the packet reached
    the host) or the maximum number of hops is exceeded (the default
    is 30 hops and can be changed with the -m option). At each ttl
    setting, traceroute launches three probes (you can change the
    number with the -q option) and prints a line showing the ttl,
    address of the gateway, and round trip time of each probe. If the
    probe answers come from different gateways, traceroute prints the
    address of each responding system. If there is no response within
    a 3 second timeout interval (which you can change with the -w
    option), an asterisk (*) is printed for that probe.

    To prevent the destination host from processing the UDP probe
    packets, the destination port is set to an unlikely value. You
    can change the destination port value with the -p option, if
    necessary.