docs: clarify how mtr probes hops

diff --git a/README.md b/README.md
index 13d8af130e1f6b0ead9efbd6e2f27542e511b736..717bd355dcf3c139ec92370f72734a438d388bea 100644 (file)
--- a/README.md
+++ b/README.md
@@ -5,11 +5,15 @@ mtr combines the functionality of the 'traceroute' and 'ping' programs
 in a single network diagnostic tool.
 
 As mtr starts, it investigates the network connection between the host
-mtr runs on and a user-specified destination host.  After it
-determines the address of each network hop between the machines,
-it sends a sequence of ICMP ECHO requests to each one to determine the
-quality of the link to each machine.  As it does this, it prints
-running statistics about each machine.
+mtr runs on and a user-specified destination host.  It sends probes to
+the destination with successively larger time-to-live values, and uses
+the responses from intervening routers to discover and measure the path.
+As it does this, it prints running statistics for each hop.
+
+Intermediate routers may be configured to never send these ICMP
+responses, or may rate-limit them, so apparent loss at an intermediate
+hop does not always mean that forwarded traffic is being lost at that
+point.
 
 mtr is distributed under the GNU General Public License version 2.
 See the COPYING file for details.