Without having made any changes to these macro defines, my agent is
already sending large response packets to getBulk queries.  These
packets are being fragmented based on a packet capture obtained
from Ethereal.  So, I'm not sure what macro define, if any, is controlling
the packet size here.  If I run the snmpd with the -Dnetsnmp_udp and
-D snmp_send debug tokens, I will get output to the effect
   snmp_send:  Building SNMPv2 message ...
   netsnmp_udp:  send 3431 bytes from ...

Is there also supposed to be a limit on the packet size that the NET-SNMP
utilities will accept?  For example, will the snmpbulkget command return
an error code or reject packets exceeding some maximum size?

Barb

-----Original Message-----
From: Robert Story [mailto:[EMAIL PROTECTED]
Sent: June 21, 2004 9:00 AM
To: Barb Roesch
Cc: [EMAIL PROTECTED]; NET-SNMP Coders (E-mail)
Subject: Re: Maximum responsePdu packet size


On Sat, 19 Jun 2004 15:08:05 -0600 Barb wrote:
BR> What is the maximum packet size that the snmpd will send?
BR> 
BR> I found the macro defines
BR> #define SNMP_MAX_MSG_SIZE 1472
BR> #define SNMP_MAX_PDU_SIZE  64000
BR> 
BR> I'm assuming the SNMP_MAX_PDU_SIZE must be the upper threshold
BR> since my getBulk requests will return a snmp payload size larger than
1472.

Interesting, because I can't find MAX_PDU_SIZE being used anywhere in the
code. MAX_MSG_SIZE, however, is used all over the place.

1472 was chosen because that is the largest size that will fit into a single
ethernet packet (1500 bytes, - ip header).

You can define MAX_MSG_SIZE to be larger, but then it is likely that your
packets will be fragmented. Since UDP is an 'unreliable' (packets aren't
confirmed, as in TCP), and SNMP was intended to help manage a failing
network, 
fragmentation is generally considered a bad thing.

-- 
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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