[Discuss] Do Cheap NAT Routers "Fill up"?

[kentborg at borg.org (Kent Borg)]

[Forgive my earlier version of this e-mail, it was confusing. I hope 
this one is better.]


A little Python is a dangerous thing...

I was running a script that does a lot of http GETs to a remote machine 
with a fast network connection (linode), and after awhile it slows down, 
and I notice other things on my computer also slow down, things like a 
DNS lookup of google.com.

I wrote an even simpler Python script that does a single packet ping of 
8.8.8.8 and then does a dig of a list of well known names (things like 
google.com, yahoo.com, ...) and I ran it in a loop: it runs fast at 
first but then slows down, with some really long pauses. Pauses of 
predictable favorite lengths.

This is over DSL. So I plugged in my phone and did a tether through it, 
and the simpler script behaves similarly: fast at first then pauses. I 
tried running the simpler script on a Linux on a different DSL network 
across the country and it worked better there, but still seemed to 
deteriorate.

Then I tried running the simpler script on my linode machine and it ran 
fine there.

The difference is the NAT? In each case where I am behind a NAT it 
starts fast and then slows down. On the one case where I had no NAT it 
ran fast. Do cheap NAT boxes not know how long to keep their translation 
records, and get plugged up?

Thanks,

-kb

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