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@ -4,37 +4,39 @@ Some details about echoping
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echo service:
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echoping assumes the remote host accepts such connections. Experience show that
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most Internet routers do and many hosts also. However, some Unices are not
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shipped with this service enabled and, anyway, the administrator is always
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free to close it (I think they shouldn't). echoping has therefore less chance
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to succeed than ping or bing. (On a typical Unix box, "echo" service is
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configured in /etc/inetd.conf but see the CERT advisory
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echoping assumes the remote host accepts such connections. Experience
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show that most Internet routers do and many hosts also. However, some
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Unices are not shipped with this service enabled and, anyway, the
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administrator is always free to close it (I think they
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shouldn't). echoping has therefore less chance to succeed than ping or
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bing. (On a typical Unix box, "echo" service is configured in
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/etc/inetd.conf but see the CERT advisory
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<http://www.cert.org/advisories/CA-96.01.UDP_service_denial.html>.)
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What does it measure?
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echoping simply shows the elapsed time, including the time to set up the TCP
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connection and to transfer the data (but excluding the time for the
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- possible - DNS call). Therefore, it is unsuitable to physical
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line raw throughput measures (unlike bing). On the other end, the action it
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performs are close from a HTTP request and it is meaningful to use it
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(carefully) to measure Web performances.
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echoping simply shows the elapsed time, including the time to set up
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the TCP connection and to transfer the data (but excluding the time
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for the - possible - DNS call). Therefore, it is unsuitable to
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physical line raw throughput measures (unlike bing). On the other end,
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the action it performs are close from a HTTP request and it is
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meaningful to use it (carefully) to measure Web performances.
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UDP and inetd:
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With UDP servers you can have surprises: the first test is quite often
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much slower since inetd has to launch the process. After that, the process
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stays a while so the next texts run faster.
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much slower since inetd has to launch the process. After that, the
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process stays a while so the next texts run faster.
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A nice example:
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There are many, many traps when measuring something on the Internet. Just one
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example: 'echoping -w 0 -n 4 a-sunOS-machine' and you'll see the first test
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succeed in a very short time (if you are close from the machine) and all of
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the others take a much longer time (one second). With '-w 1' (wait one second
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between tests, the default), everything works fine: it seems the sockets on
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SunOS need time to recover :-)
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There are many, many traps when measuring something on the
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Internet. Just one example: 'echoping -w 0 -n 4 a-sunOS-machine' and
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you'll see the first test succeed in a very short time (if you are
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close from the machine) and all of the others take a much longer time
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(one second). With '-w 1' (wait one second between tests, the
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default), everything works fine: it seems the sockets on SunOS need
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time to recover :-)
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To measure performances on the Internet you can also see:
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@ -75,9 +77,9 @@ MS-Windows:
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Windows-NT :
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echo and other services can (apparently) be provided within
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'Simple TCP/IP Services' which
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can be enabled through the Network Control Panel
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echo and other services can (apparently) be provided within 'Simple
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TCP/IP Services' which can be enabled through the Network Control
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Panel
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Web clients:
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@ -89,10 +91,10 @@ Web clients:
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Use all of them with care, the result is not obvious to interpret.
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And don't forget to read RFC 1470 ("Tools for Monitoring and Debugging
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TCP/IP Internets and Interconnected Devices"), specially its "Benchmark"
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section and the Richard Stevens' books (all of them), published by
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Addison-Wesley.
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And don't forget to read RFC 1470 ("Tools for Monitoring and Debugging
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TCP/IP Internets and Interconnected Devices"), specially its
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"Benchmark" section and the Richard Stevens' books (all of them),
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published by Addison-Wesley.
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$Id$
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