[AusNOG] Help with TPG EFM MTU size

[Goran Aleksic]

Hi all,

had a read on TPG EFM NTU size and I saw in an older post it was important
which LAC  you connect to etc.

In my case, got a customer on TPG EFM service who needed to migrate from
EdgeRouter to Juniper SRX to enable some features.
However, after migration, intermittent issues started with Internet Banking
and other web sites using TLS/SSL encryption.
Intermittent issues had no pattern, there was no link congestion at the
time I witnessed those.
Bandwidth speed tests were giving me expected results.
On the other side, remote desktop access, IPSec tunnel, IP Telephony all
worked well.
In the migration I observed MTU size on the old router and configured
Juniper SRX accordingly.
However, got the intermittent issues to go away only after I decreased MTU
/ TCP-MSS from 1492 to 1440 / 1400 B.
I got a case with TPG and they insisted on isolation test, which I did with
laptop, old router and new router (all 3 without specifying MTU size) and
managed to ping as big as
1. 1272 on laptop directly plugged into NTU
2. 1412 after NTU reboot
3. 1412 from Juniper SRX after NTU reboot
4. 1412 from laptop behind Juniper SRX after NTU reboot
5  1272 from laptop behind EdgeRouter after NTU reboot

This is all quite confusing.
On top of that TPG denies anything wrong and asks me to do isolation test
again (ya, right, we got no other business but to take customers offline
and do isolation tests...)

They don't seem to appreciate I had to troubleshoot this and find out the
MTU size by trial and error, while it should be deterministic and standard,
as outlined in service activation notice.

They also ignore the fact that decreased MTU impacts the link efficiency
and customer's capacity to use the service in an optimal way.

I wondered if anyone can help me make sense out of this?
What arguments can I use to get TPG to investigate properly?

Many thanks!
Goran
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