On Fri, Sep 16, 2011 at 2:42 PM, Steve Bohrer <skboh...@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