FreeRadius Losing packets in Multi-Threads mode

Bjørn Mork bjorn at
Tue Oct 25 20:15:46 CEST 2011

Andrej <andrej.groups at> writes:
> On 26 October 2011 04:48, Bjørn Mork <bjorn at> wrote:
>>>   If the server is too slow to process requests, the kernel will throw
>>> away the UDP packets.  This happens when the server is slow... whether
>>> it's threaded or not.
>> But then the client won't get the acks and retransmit.  If I understood
>> correctly, then the problem is the packets *are* acked but not logged.
> Maybe my whole understanding of UDP is flawed, I thought the whole
> point of using UDP instead of TCP is not to have ACKS and retransmits?

Not nessarily.  The point is that UDP leaves that up to the
application.  For RADIUS accounting this is described in

   It is recommended that
   the client continue attempting to send the Accounting-Request packet
   until it receives an acknowledgement, using some form of backoff.  If
   no response is returned within a length of time, the request is re-
   sent a number of times.  The client can also forward requests to an
   alternate server or servers in the event that the primary server is
   down or unreachable.  An alternate server can be used either after a
   number of tries to the primary server fail, or in a round-robin
   fashion.  Retry and fallback algorithms are the topic of current
   research and are not specified in detail in this document.

I don't know if all clients follow this recommendation, but a lot of
them do.


More information about the Freeradius-Users mailing list