Traceroute losses through NYC1.gblx.net?

Christopher Morrow morrowc.lists at gmail.com
Fri Sep 16 13:53:17 CDT 2011


On Fri, Sep 16, 2011 at 2:42 PM, Steve Bohrer <skbohrer at 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



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