[144671] in North American Network Operators' Group
Re: Traceroute losses through NYC1.gblx.net?
daemon@ATHENA.MIT.EDU (Christopher Morrow)
Fri Sep 16 14:54:12 2011
In-Reply-To: <CE188505-3E93-4F9E-94E2-C65EA0B7C7B7@simons-rock.edu>
Date: Fri, 16 Sep 2011 14:53:17 -0400
From: Christopher Morrow <morrowc.lists@gmail.com>
To: Steve Bohrer <skbohrer@simons-rock.edu>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Fri, Sep 16, 2011 at 2:42 PM, Steve Bohrer <skbohrer@simons-rock.edu> wrote:
> Can I expect that backbone routers should never give me timeouts on a
> traceroute through them, so, lots of asterisks from these systems indicate a
> packet loss problem that needs to be fixed?
something inside the router has to make the icmp-unreachable-ttl-expired, right?
perhaps that thing is rate-limited (in hardware/software) so that a
line-rate flood of ttl=1 packets won't induce an outbound dos attack
effect?
perhaps that is a shared resource among all of the ports on the
pic/card/chassis?
perhaps the function that does this does more than just make
ttl-expired? (other error codes or other ancillary functions)
> Or, are these traceroute asterisks essentially meaningless, and should be
> expected on any busy link?
think router not link, but.... probably less important that you don't
see ttl-expired messages, but that you do see no packet
loss/mal-effects with the protocols you care about (ping? http? smtp?)
it's also possible that the destination has requested gblx to filter
udp toward it (depending on what sort of a day they are having and how
much fun gblx wants to incur)
-chris
