Packet loss simulation + PFsync documentation

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Packet loss simulation + PFsync documentation

Quentin Aebischer
Hello everyone,

I've been searching around and couldn't find a full description of the  
pfsync header format and all the different types of messages (some  
kind of RFC).
Do you guys know whether or not there exists such a document ? or  
something similar that would review in details al the types of  
messages for pfsync ?

I've read David Gwynne's paper about pfsync_v5  
(, and he gives a quick list of the  
different message types, but its work is 2 years old and maybe the  
protocol evolved since then ? Are there no other message types in the  
current implementation ?

Also, does the protocol implement some kind of reliability mechanism,  
like message sequencing / acknowledgements messages ? How would pfsync  
behave in an environment with limited bandwith and subject to packets  
loss ?

Lastly, I'd like to test pfsync in a simulated environment with  
potential packets loss/corruptions and/or with limited bandwith.

I know I can emulate packets loss by adding probability to a block  
rule in pf.conf, and I'm not sure but I think ALTQ could help to add  
some bandwith limitation (though its main goal is more to implement  
QoS rules, again correct me if I'm wrong).
I've heard of Dummynet for FreeBSD ; is there  the equivalent for OpenBSD ?

Thanks for reading me,


Quentin Aebischer
University of Sherbrooke,