[Bloat] How is bufferbloat prevented/fixed for UDP?

Hal Murray hmurray at megapathdsl.net
Tue May 13 00:33:28 EDT 2014

> 1)With UDP, you cannot uniquely identify a flow? This prevents an
> AQM-algorithm to drop packets for an (several) offending UDP flow(s). 

UDP packets have port numbers, just like TCP.

> 2) Unlike TCP, UDP does not back down when encountering packet loss 

Mumble.  The OS doesn't do it.  It has to be done in user code.  But there is 
no reason that it can't be done there even if it isn't done correctly as 
often as we might like.

I think most DNS code is reasonably sane, mostly because the retransmit 
timeout is several seconds and also because it only retransmits a few times.

The poster child for how to do it wrong is the NTP client that was shipped in 
a zillion Netgear home routers with a hard wired NTP server.  Dave Plonka did 
a wonderful writeup.
I call it required reading (and understanding) for anybody interested in 

These are my opinions.  I hate spam.

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