Hi,

The great Cisco TRex team [1] has updated their performance testing software so 
that it can now test NAT64 boxes! They added an Advance Stateful mode (ASTF) 
that implements an extremely fast TCP stack for testing [2]. Naturally I 
pointed it at a Jool box :-)  Unfortunately the Jool box collapsed under the 
surge of new sessions :-(

Some observations:
- At the beginning of the test the performance seems fine (2.5Gbit/s in my test)
- When a lot of flows are created the box starts dropping packets massively and 
performance collapses
- The BIB logging actually still shows new sessions being created

From this it seems that the session table is a performance bottleneck. Not 
surprising for a stateful protocol :-)  But because Jool still creates new 
sessions but starts dropping packets of existing sessions it also seems that 
session creation has a higher priority than packet forwarding. Could it be that 
session creation locks the session table, and that the increased size of the 
table keeps the locks blocked for longer and longer?

Q1: any disagreements with my interpretation? ;-)
Q2: what can we do to improve this?

Cheers,
Sander

PS: Developers that want to work on this and would like access to my lab boxes 
(Dell R630 with lots of cores, memory and some 10Gbit/s NICs): feel free to 
contact me!

[1] https://trex-tgn.cisco.com
[2] https://trex-tgn.cisco.com/trex/doc/trex_astf.html

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