echoping/SRC/ttcp

"echoping" is a small program to test (approximatively) performances of a 
remote host by sending it TCP "echo" packets.

It 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.)

In any case, be polite: don't bother the remote host with many repeated 
requests, especially with large size.

The current version is very rough. It was written quickly and not debugged 
in detail.

It appears to compile and run at least on OSF/1 3.2, Solaris (?),
Linux 1.1, SunOS 4.1 and Ultrix 4.3. You do not have to be root to 
install it: just type make and copy the "echoping" executable anywhere you 
want. There is no man page.

To use it, simply:

% echoping machine.somewhere.org

or use the options before the machine name:

-v : verbose
-s nnn : size of the data to send
-n nnn : numbers of repeated tests
-w nnn : number of seconds to wait between two tests (default is one)
-t nnn : number of seconds to wait a reply before giving up
-u : use UDP instead of TCP
-d : use the "discard" service instead of echo
-c : use the "chargen" service instead of echo

echoping simply shows the elapsed time, including the time to set up the TCP 
connection and to transfer the data. 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.

With the '-n' option, you have also the minimum, maximum, average and median
time. The median is the value such that half of the measures are under it
and the other half is above. When you measure highly variables values, like
it is often the case on the whole Internet, median is better than average
to avoid  "extreme" values.

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 :-)

With UDP servers you can have other 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.

If you have the Perl/Tk <http://pubweb.bnl.gov/~ptk/> package, you can use a 
(quite rough) windowing interface, "echoping.ptk". To use it, you should 
define FLUSH_OUTPUT at the beginning of echoping.c (this seems to work
on only a few Unices, including DEC's OSF/1).

Known bugs: 

- UDP isn't really useable with large packets because of sockets 
  limitations and the lack of workaround code

To do:

- display statistics even when interrupted by Control-C
- display other calculations such as standard deviation
- timeouts even on TCP connections

To measure performances on the Internet you can also see:

Unix:

- bing, a bandwidth measurement tool <ftp://ftp.ibp.fr/pub/networking>
- ping, probably available with your system
- traceroute, idem (otherwise, see <ftp://ftp.ee.lbl.gov/>)
- ttcp, the best measurement tool but it needs some control over the 
  two machines <ftp://ftp.arl.mil/pub/ttcp>
- spray is a tool which I dont't know very well. It is available on some 
  machines (Sun, OSF/1).
I've also heard of but never tried:
- NetPerf <http://www.cup.hp.com/netperf/NetperfPage.html>
- a suite of Bandwidth Measuring programs from gnn@netcom.com 
  <ftp.netcom.com/~ftp/gnn/bwmeas-0.3.tar.Z>. These are several 
  programs that measure bandwidth and jitter over several kinds of 
  IPC links, including TCP and UDP.
  
Macintosh:

- TCP Watcher, a very nice "swiss-army knife" tool, to test ping, DNS, echo. 
  It includes an echo server. Available on Info-Mac in "comm/tcp".
  
Web clients:

- You can ping or traceroute on the Web. See 
  <http://hplyot.obspm.fr/cgi-bin/nph-traceroute>, <http://www.fr.net/>,
  and <gopher://ns.urec.fr/11/Reseaux/Annuaires>.


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.


The reference site for echoping is:

ftp://ftp.pasteur.fr/pub/Network/echoping

Stephane Bortzmeyer <bortzmeyer@pasteur.fr>. October 1995 for the
first version. December 1995 for this one.