#use wml::template Title="echoping details"

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<H2>echo service</H2>

<P>echoping, with its default setting, assumes the remote host accepts
such connections. Experience show that most Internet routers or hosts
do not. 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 <A
HREF="http://www.cert.org/advisories/CA-1996-01.html">CERT
advisory</A>.)

<H2>What does it measure?</H2>

<P>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. 

<H2>UDP and inetd</H2>

<P>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.

<H2>A nice example</H2>

<P>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 :-)

<H2>To measure performances on the Internet you can also see</H2>

<H3>Unix</H3>

<UL>
<LI><A
  HREF="http://www.freenix.fr/freenix/logiciels/bing.html">bing</A>, a
  bandwidth measurement tool
<LI>pathchar or <A
  HREF="http://www.employees.org/~bmah/Software/pchar/">pchar, a bandwidth measurement tool
<LI>ping, probably available with your system
<LI>traceroute, idem (otherwise, see <A HREF="ftp://ftp.ee.lbl.gov/">LBL</A>)
<LI><A HREF="ftp://ftp.arl.mil/pub/ttcp/">ttcp</A>, the best measurement tool but it needs some control over the 
  two machines 
<LI><A HREF="ftp://ftp.scl.ameslab.gov/pub/netpipe/">Netpipe</A>, it needs some control over the two machines 
<LI><A HREF="http://www.psc.edu/~pscnoc/treno_info.html">treno</A> (evaluates available bandwidth for TCP) 
<LI>spray is a tool which I dont't know very well. It is available on some 
  machines (Sun, OSF/1).
<LI>I've also heard of but never tried:
<UL>
<LI><A
  HREF="http://www.netperf.org/netperf/NetperfPage.html">Netperf</A>, a suite of Bandwidth Measuring programs from gnn@netcom.com 
  These are <A HREF="ftp://ftp.netcom.com/~ftp/gnn/bwmeas-0.3.tar.Z">several 
  programs</A> that measure bandwidth and jitter over several kinds of 
  IPC links, including TCP and UDP.
</UL>
</UL>

<H3>MacOS</H3>

<UL>
<LI>TCP Watcher, a very nice "swiss-army knife" tool, to test ping, DNS, echo. 
  It includes an echo server. Available on <A
  HREF="http://www.info-mac.org/">Info-Mac</A> in "comm/inet".
</UL>

<H3>MS-Windows</H3>

(I have little knowledge of that environment and I tested nothing.) 

<UL>
<LI><A
HREF="http://www.ccs.org/winsock/xref-e.html#echo_clients">WSNUTIL</A>.
Seems to be an echo client and server. 
<LI><A
HREF="http://www.winsite.com/info/pc/win95/misc/echox32.zip/">echox32</A>,
an echo server
<LI><A
HREF="http://www.winsite.com/info/pc/win3/winsock/cfing13b.zip/">cfinger</A>,
an
echo client and server
</UL>
  
<H3>Windows-NT</H3>

echo and other services can (apparently) be provided within
'Simple TCP/IP Services' which
can be enabled through the Network Control Panel

<H3>Web clients</H3>

You can ping or traceroute on the Web. See <A
HREF="http://www.traceroute.org/">traceroute.org</A>.

<P>Use all of them with care, the result is not obvious to interpret.

<P>If you are interested in Internet measurements, there is an <A
HREF="http://www.ietf.org/">Internet Engineering Task Force</A>
Working Group, <A
HREF="http://www.ietf.org/html.charters/ippm-charter.html">IPPM (IP
Performance Metrics)</A> which produces many fine RFC that are really
good to read. I appreciate RFC 2330 and 3148.

<P>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.