With the recent addition of the ability to set the buffers size for UDP and TCP
sockets in 5.2, it seems like a good time to revisit the question of what the
default value should be. The current behavior is to set them to 128k, which
seems rather large. The rational, from the CVS log message:
- set SO_SNDBUF and SO_RCVBUF to 128Kb for newly-opened UDP sockets,
to enable large PDUs to be sent and received. Some
implementations default very low (Solaris 2.7 8Kb, Linux 2.4
64Kb).
The other important bit of information about socket size is that if affects the
number of packets that can be received while a process is busy. The original
author of the patch to allow increased buffers sizes was motivated by the fact
that his snmptrapd was losing packets due to an insufficient receive buffer.
The new patch allows on to set independent buffer sizes for client vs server,
and send vs receive. Given that SNMP_MAX_PDU_SIZE is less than 64k, a default
buffer size of 128k seems excessive.
I suggest that:
1) snmpd and snmptraps both set the default receive buffers size to at least
128k, if not more, to minimize the changes of missing packets.
2) if no buffer size is specified, that the default be to use the default size
specified by the OS. I'm guessing that the average PDU is pretty small (<1k),
so the OS defaults are probably very safe.
Thoughts, opinions and arguments welcomed.
--
Robert Story; NET-SNMP Junkie <http://www.net-snmp.org/>
<irc://irc.freenode.net/#net-snmp>
Archive: <http://sourceforge.net/mailarchive/forum.php?forum=net-snmp-coders>
You are lost in a twisty maze of little standards, all different.
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