diff --git a/SRC/DETAILS b/SRC/DETAILS index e44ddd7..79eed87 100644 --- a/SRC/DETAILS +++ b/SRC/DETAILS @@ -4,37 +4,39 @@ Some details about echoping echo service: -echoping assumes the remote host accepts such connections. Experience show that -most Internet routers do and many hosts also. However, some Unices are not -shipped with this service enabled and, anyway, the administrator is always -free to close it (I think they shouldn't). echoping has therefore less chance -to succeed than ping or bing. (On a typical Unix box, "echo" service is -configured in /etc/inetd.conf but see the CERT advisory +echoping assumes the remote host accepts such connections. Experience +show that most Internet routers do and many hosts also. However, some +Unices are not shipped with this service enabled and, anyway, the +administrator is always free to close it (I think they +shouldn't). echoping has therefore less chance to succeed than ping or +bing. (On a typical Unix box, "echo" service is configured in +/etc/inetd.conf but see the CERT advisory .) What does it measure? -echoping simply shows the elapsed time, including the time to set up the TCP -connection and to transfer the data (but excluding the time for the -- possible - DNS call). Therefore, it is unsuitable to physical -line raw throughput measures (unlike bing). On the other end, the action it -performs are close from a HTTP request and it is meaningful to use it -(carefully) to measure Web performances. +echoping simply shows the elapsed time, including the time to set up +the TCP connection and to transfer the data (but excluding the time +for the - possible - DNS call). Therefore, it is unsuitable to +physical line raw throughput measures (unlike bing). On the other end, +the action it performs are close from a HTTP request and it is +meaningful to use it (carefully) to measure Web performances. UDP and inetd: With UDP servers you can have surprises: the first test is quite often -much slower since inetd has to launch the process. After that, the process -stays a while so the next texts run faster. +much slower since inetd has to launch the process. After that, the +process stays a while so the next texts run faster. A nice example: -There are many, many traps when measuring something on the Internet. Just one -example: 'echoping -w 0 -n 4 a-sunOS-machine' and you'll see the first test -succeed in a very short time (if you are close from the machine) and all of -the others take a much longer time (one second). With '-w 1' (wait one second -between tests, the default), everything works fine: it seems the sockets on -SunOS need time to recover :-) +There are many, many traps when measuring something on the +Internet. Just one example: 'echoping -w 0 -n 4 a-sunOS-machine' and +you'll see the first test succeed in a very short time (if you are +close from the machine) and all of the others take a much longer time +(one second). With '-w 1' (wait one second between tests, the +default), everything works fine: it seems the sockets on SunOS need +time to recover :-) To measure performances on the Internet you can also see: @@ -75,9 +77,9 @@ MS-Windows: Windows-NT : -echo and other services can (apparently) be provided within -'Simple TCP/IP Services' which -can be enabled through the Network Control Panel +echo and other services can (apparently) be provided within 'Simple +TCP/IP Services' which can be enabled through the Network Control +Panel Web clients: @@ -89,10 +91,10 @@ Web clients: Use all of them with care, the result is not obvious to interpret. -And don't forget to read RFC 1470 ("Tools for Monitoring and Debugging -TCP/IP Internets and Interconnected Devices"), specially its "Benchmark" -section and the Richard Stevens' books (all of them), published by -Addison-Wesley. +And don't forget to read RFC 1470 ("Tools for Monitoring and Debugging +TCP/IP Internets and Interconnected Devices"), specially its +"Benchmark" section and the Richard Stevens' books (all of them), +published by Addison-Wesley. $Id$