udp packets drop

[S H A N]

hi,
 	i have a radius server running p3/1GB ram called yoyo. below is what has happened to it... 

[root at yoyo:~]$ netstat -s -s -p udp
udp:
        5397 datagrams received
        186 dropped due to full socket buffers
        5198 delivered
        5207 datagrams output
[root at yoyo:~]$ netstat -i -b -d
Name  Mtu   Network       Address            Ipkts Ierrs     Ibytes    Opkts Oerrs     Obytes  Coll Drop
fxp0  1500  <Link#1>    00:c0:4f:01:15:9d   149570     0   10018080    13882     0    7040614     0   0
fxp0  1500  yyy.yyy.yyy.yyy yoyo             12807     -    1612355    13732     -    6840464     -   -
fxp1  1500  <Link#2>    00:90:27:e5:bc:d4   596777     0   40928713   111791     0   10794960     0   0
fxp1  1500  192.168.192   192.168.192.13    111913     -   10269671   111726     -    9227484     -   -
fxp2  1500  <Link#3>    00:90:27:e5:b5:5a        0     0          0        1     0         42     0   0
fxp2  1500  192.168.193   192.168.193.13         0     -          0        0     -          0     -   -
lo0   16384 <Link#4>                           133     0      74619      133     0      74619     0   0
lo0   16384 your-net      localhost            133     -      74619      133     -      74619     -   -
[root at yoyo:~]$ netstat -m
202/624/131072 mbufs in use (current/peak/max):
        200 mbufs allocated to data
        2 mbufs allocated to packet headers
198/406/32768 mbuf clusters in use (current/peak/max)
968 Kbytes allocated to network (0% of mb_map in use)
0 requests for memory denied
0 requests for memory delayed
0 calls to protocol drain routines

since yoyo needs to be tuned for udp performance, here is what i got in /etc/sysctl.conf

kern.ipc.maxsockbuf=2097152
net.inet.udp.recvspace=65535
net.inet.udp.maxdgram=57344
net.inet.udp.blackhole: 1

and compiled the kernel with these options

machine         i386
cpu             I686_CPU
ident           yoyo
maxusers        1024
options         NSFBUFS=1024
options         NMBCLUSTERS=32768

ok. now the question is... yoyo complains that 186 udp packets dropped due to full socket buffers. so how to avoid loosing any packet? 
please help this freebsd newbie.

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