IP Fragmentation - Not reliable over the Internet?

Benno Overeinder benno at NLnetLabs.nl
Fri Aug 30 14:36:39 UTC 2013

On 08/30/2013 01:58 PM, Randy Bush wrote:
>> In a study using the RIPE Atlas probes, we have used a heuristic to
>> figure out where the fragments where dropped.  And from the Atlas
>> probes where IP fragments did not arrive, there is a high likelihood
>> the problem is with the last hop to the Atlas probe.
> i wonder if this is correlated with the high number of probes being
> behind nats.

That would be a viable explanation, although we have not tried to
fingerprint the probes to figure out if this was true.

If we will rerun the experiments in the future, we should spent more
effort into identifying the router/middlebox that is giving the IP
fragmentation problems (drops or blocking PMTUD ICMP).

-- Benno

Benno J. Overeinder
NLnet Labs

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