Completely reformated

GETADDRINFO
Stephane Bortzmeyer 24 years ago
parent bcc4468a34
commit 20c1318a36

@ -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
<http://www.cert.org/advisories/CA-96.01.UDP_service_denial.html>.)
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.
$Id$

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