On Wed, 7 Sep 2005, Christopher L. Morrow wrote:
On Tue, 6 Sep 2005 sdb@stewartb.com wrote:
On Tue, 6 Sep 2005, Christopher L. Morrow wrote:
On Tue, 6 Sep 2005, chip wrote:
On 9/6/05, Joe Maimon <jmaimon@ttec.com> wrote:
If the hop(s) following the one you see loss for shows no loss, then disregard the loss for that hop, obviously whatever it is, it does not affect transit, which is what you really want to know.
Is that correct?
This is one of the most misunderstood concepts in properly reading output from a traceroute (mtr, visualtraceroute, whatever). Basically you are seeing loss of packets destined directly *TO* that router, not THRU it. Most
no... not destined TO the router, destined THROUGH the router that happen to TTL=0 ON that router.
Very true. Most backbone kit on a tier 1 network is designed to switch
I was really just pointing out that 'traceroute' or 'mtr' send packets with increasing TTL to show 'loss' or 'delay' from place to place, I wasn't trying to debate the every-changing reasons why backbone equipment might or might not answer 'ttl-expired' or 'unreachable' (or any 'exception traffic' really) in a 'timely' fashion. That issue changes with the wind/os/hardware/model.... :)
Yeah, it was a sweeping generalisation, hence the excessive use of words such as "usually" and "most" :) I was trying to put the point across as to why things are like this, for those that might be wondering why. The main point was actually that the ability of a device (router, web server etc) to deal with stuff _like_ ICMP message generation does not reflect its ability to perform it's main task.
nice to L3 sending in the answer police though :) Thanks!
Thanks :) SB -- Stewart Bamford (Posting as an individual) Level3 Snr IP Engineer *** Views expressed are my own and not necessarily those of Level3 *** Primary email stewart@whoever.com Secondary email me@stewartb.com Personal website http://www.stewartb.com/