North American Network Operators Group
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Re: Recommendation of Tools

  • From: Anders Lindbäck
  • Date: Wed Dec 03 13:02:00 2008
Mtr is even less usefull then that, in its default mode it does a traceroute and then proceeds to ICMP Ping flood each IP in the list generated by the traceroute, the result is usually completly useless on WAN topologies due to asym-routing, ICMP node protections by carriers and punting etc..

And using UDP will not really provide better results due to the same thing, and IIRC Cisco from 12.0 has a standard setting of no more then 1 ICMP Unreach per 500ms..

------------------------------
Anders Lindbäck
[email protected]


On 3 dec 2008, at 12.00, Pekka Savola wrote:

On Tue, 2 Dec 2008, Antonio Querubin wrote:
On Wed, 3 Dec 2008, Pekka Savola wrote:
FWIW, Mtr measures latency/delay and loss based on ICMP messages heard
back from the routers on path. As a result, in almost all cases, the real
hop-by-hop latency of actual end-to-end data packets is better than it can
report.

mtr has a recently added '-u' option to use UDP instead of ICMP echo requests.

But that doesn't change the gist of my message: it's still relying on ICMP ttl exceeded messages sent by the routers on the path to check the delays etc. As such it suffers from basically the same limitations as ICMP probing.

--
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings