RINA - scott whaps at the nanog hornets nest :-)

George Bonser gbonser at seven.com
Sat Nov 6 22:26:40 CDT 2010


> 
> I prefer much less packet loss in a majority of my transmissions,
which
> in turn brings those numbers closer together.
> 
> 
> Jack

True, though t the idea that it greatly reduces packets in flight for a
given amount of data gives a lot of benefit, particularly over high
latency connections.  Considering throughput <= ~0.7 * MSS / (rtt *
sqrt(packet_loss)) (from http://sd.wareonearth.com/~phil/jumbo.html) and
that packet loss to places such as China is often greater than zero, the
benefits of increased PMTU become obvious.  Increase that latency from
20ms to 200ms and the benefits of increased MSS are obvious.

The only real argument here against changing existing peering points is
"all peers must have the same MTU".  So far I haven't heard any real
argument against it for a new peering point which is starting from a
green field. It isn't going to change how anyone's network behaves
internally and increasing MTU doesn't produce PMTU issues for transit
traffic.  

It just seems a shame that two servers with FDDI interfaces using SONET
long haul are going to perform much better on a coast to coast transfer
than a pair with a GigE over ethernet long haul simply because of the
MTU issue.  Increasing the bandwidth of a path to GigE shouldn't result
in reduced performance but in this case it would.

At least one peering point provider has offered to create a jumbo VLAN
for experimentation.





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