Why are XFRs to Secondaries equally fast?

[Klaus Darilion]

Hello!

Yesterday I made some tests transferring a zone with 50mio RRs to 35 Secondaries. I measured the time between:

-          Primary logs "zone test/IN: sending notifies"

-          Primary logs "client xxxx: transfer of 'test/IN': AXFR-style IXFR ended"

What makes we wonder is, that for several secondaries the XFR duration is equally fast although these secondaries are globally distributed with different RTTs and different VMs:
173  seconds
173  seconds
404  seconds
405  seconds
609  seconds
620  seconds
622  seconds
638  seconds
838  seconds
838  seconds
839  seconds
839  seconds
843  seconds
848  seconds
859  seconds
1031 seconds
1032 seconds
1032 seconds
1035 seconds
1037 seconds
1038 seconds
1038 seconds
1038 seconds
1043 seconds
1702 seconds
2359 seconds
2361 seconds
2361 seconds
2361 seconds
2361 seconds
2361 seconds
2361 seconds
2361 seconds
2361 seconds
2362 seconds

For example, there are 8 secondaries (Mumbai, LosAngeles, Melbourne, Atlante, SaoPaulo...) to which the XFR took 2361 seconds.


Are there some mechanisms in Bind that put multiple XFRs together into a common stream? Or do you have any other ideas how it come that several XFRs are equally fast?

Thanks
Klaus


--
Klaus Darilion, Head of Operations
nic.at GmbH, Jakob-Haringer-Straße 8/V
5020 Salzburg, Austria
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/bind-users/attachments/20230727/aed32459/attachment.htm>