MTU of the Internet?

FWIW, our router at MAE-East says:

IP packet size distribution (38569M total packets):
   1-32 64 96 128 160 192 224 256 288 320 352 384 416 448 480
   .000 .400 .046 .016 .018 .012 .008 .009 .011 .012 .006 .007 .005 .004 .004

    512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
   .010 .006 .120 .000 .099 .197 .000 .000 .000 .000 .000

It's been up for some weeks and the sample size is, well, OK. As
expected, large number at the low end, but I'm not sure what to think
about the 2048 slot. I would have thought that once packets are bigger
than ethernet MTU, they would also be bigger than 2048. If the
numbers are true, then close to 1/3 of all packets (1536 slot plus 2048
slot) are larger than 576.

Bug. I believe counters a shifted by one slot from 1024. As you'll note
that that slot is empty.

-dorian

FWIW, our router at MAE-East says:

IP packet size distribution (38569M total packets):
   1-32 64 96 128 160 192 224 256 288 320 352 384 416 448

480

   .000 .400 .046 .016 .018 .012 .008 .009 .011 .012 .006 .007 .005 .004

.004

    512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
   .010 .006 .120 .000 .099 .197 .000 .000 .000 .000 .000

It's been up for some weeks and the sample size is, well, OK. As
expected, large number at the low end, but I'm not sure what to think

Bug. I believe counters a shifted by one slot from 1024. As you'll note
that that slot is empty.

-dorian

I'll bet that is true, since histograms for the last couple of years have
shown clusters at 40, 512, 576, 1024 and a tiny bit of 1500. Looks like it
hasn't changed much since.

--Kent

Yes, that's what one would suspect, but it's been like that ever since
flowswitching was first introduced (which, of course, doesn't
necessarily mean anything). In any case, the interesting part is that
30% of all packets would still be larger than 576, with probably close
to 20% being larger than 2*576, meaning that an "enforced" MTU of 576
would lead to a very substantial increase in packet count. This would
be a big step in the wrong direction. (On that note, I'm actually not
sure about the wisdom of MTU discovery in the Internet, given the large
number of dial-up users. The way to go is to send big packets and
fragment in the access server if the user has negotiated a small MRU.)