TCP Prague in ns-3: Pacing Rate hits 0 bps

[Maria Eduarda Veras Martins]

Hey everyone,

I'm trying to use TCP Prague in ns-3 with code from a Google project (link), but my simulation crashes when the pacing rate becomes 0 bps. I've noticed the function updating the pacing rate seems to be SocketBase::UpdatePacingRate().

Should TCP Prague have its own dedicated function for this, or am I missing something in how it interacts with the base socket's pacing?

Any ideas on how to fix this, or can anyone point me to a working TCP Prague ns-3 repository or offer implementation tips?

Thanks!

[Gabriel Ferreira]

I think this is better suited for upstream ns-3-users. In any case, floating point exception (SIGFPE).
You just need to debug and check whether it was division/multiplication by NaN, division by zero, or the other possible cases for that, and trace it back.
It is usually someone forgetting to put a +1 to denominators. =x
Also, find it very suspicious ssthresh value. It is unsigned 32bit limit.

[Maria Eduarda Veras Martins]

Hi Gabriel,

I found the problem! The TCP state is CA_CWR, and in the Prague implementation, HasCongControl isn't set to true. It seems CongControl wasn't used at all, only PktsAcked. Because of this, the window is set to 0 in that part of the code, leading to a division by zero error.

I'm a bit confused about the PktsAcked and CongControl functions, especially regarding when to use each of them. Could you help me understand them better? I'll be doing some more research on my end as well.

Thank you

[Tom Henderson]

Maria, that implementation is out of date and was not complete.  There is an updated implementation around but it is not on a public branch; I'll see if I can obtain an updated version.

- Tom

--
You received this message because you are subscribed to the Google Groups "5G-LENA-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 5g-lena-user...@googlegroups.com.
To view this discussion, visit https://groups.google.com/d/msgid/5g-lena-users/4216cceb-0d23-45bf-9939-b82d605f5855n%40googlegroups.com.

[Maria Eduarda Veras Martins]

Hi Tom, that would help a lot!!

Thank you very much.