[92924] in North American Network Operators' Group
Re: Refusing Pings on Core Routers??? A new trend?
daemon@ATHENA.MIT.EDU (Fergie)
Fri Oct 20 00:56:33 2006
From: "Fergie" <fergdawg@netzero.net>
Date: Fri, 20 Oct 2006 04:55:11 GMT
To: rubensk@gmail.com
Cc: nanog@merit.edu
Errors-To: owner-nanog@merit.edu
IIRC, this is not news.
- ferg
-- "Rubens Kuhl Jr." <rubensk@gmail.com> wrote:
> template response -- I hear is "Well, you can't rely on traceroute
> because of ICMP prioritisation". When you start to explain how
> traceroute actually works (both ICMP-based and UDP-based (which
> still relies on ICMP responses, of course!)), and that ICMP prio
> should only affect the IP of which the router listens on (and not
> hops beyond or at the dest), most NOCs fire back with another
If I recall well, Cisco GSRs impose low priority and/or limits for all
ICMP traffic flowing thru the box, not just packets to/from router
itself, and there's not a knob to adjust that.
Also of notice is that packets that expire TTL needs some kind of
low-path processing, and will be subject to increased latency or loss
compared to normal ones, and this affects every tool to trace packets
thru the network I've seen.
--
"Fergie", a.k.a. Paul Ferguson
Engineering Architecture for the Internet
fergdawg(at)netzero.net
ferg's tech blog: http://fergdawg.blogspot.com/
