Packet loss problem

[Colin Watson]

Hi, I've got a rather strange issue with UDP loss (at least I think it is) on my network, and frankly - I'm not sure it's me (think it might be the upstream providers stuff). Basically, the situation is this, FreeBSD 4.8 box connects to the upstream provider, and another one at another location acts as a gateway for the customers. The gateway box has very high 'drops' on it's UDP sockets, making streaming stuff awful - and output of netstat -s (UDP,TCP & IP only) on the gateway box is shown at the end of this post. My particular concern is these lines in the UDP output "41738 datagrams received
  / 33104 broadcast/multicast datagrams dropped due to no socket " which seems an inordinatly high amount. There are no drops due to full socket buffers, although I have recompiled the kernel with nmbclusters=8192 and Maxusers=1024 (to increase number of available sockets - kern.ipc.maxsockets to 9391), still the loss occurs. Any suggestions, and could someone explicitly explain what "broadcast/multicast datagrams dropped due to no socket"  means.

Many Thanks


Colin.

---> Output of netstat -s on Gateway Box ----->

tcp:
        40102 packets sent
                14837 data packets (1080215 bytes)
                23 data packets (29468 bytes) retransmitted
                0 resends initiated by MTU discovery
                17949 ack-only packets (669 delayed)
                0 URG only packets
                0 window probe packets
                6924 window update packets
                370 control packets
        46602 packets received
                10485 acks (for 1080288 bytes)
                227 duplicate acks
                0 acks for unsent data
                31029 packets (31656794 bytes) received in-sequence
                132 completely duplicate packets (177030 bytes)
                0 old duplicate packets
                9 packets with some dup. data (3920 bytes duped)
                7375 out-of-order packets (9107920 bytes)
                0 packets (0 bytes) of data after window
                0 window probes
                11 window update packets
                0 packets received after close
                0 discarded for bad checksums
                0 discarded for bad header offset fields
                0 discarded because packet too short
        182 connection requests
        14 connection accepts
        0 bad connection attempts
        0 listen queue overflows
        190 connections established (including accepts)
        258 connections closed (including 1 drop)
                19 connections updated cached RTT on close
                19 connections updated cached RTT variance on close
                9 connections updated cached ssthresh on close
        5 embryonic connections dropped
        9539 segments updated rtt (of 9546 attempts)
        9 retransmit timeouts
                0 connections dropped by rexmit timeout
        0 persist timeouts
                0 connections dropped by persist timeout
        0 keepalive timeouts
                0 keepalive probes sent
                0 connections dropped by keepalive
        1 correct ACK header prediction
        27603 correct data packet header predictions
        15 syncache entries added
                1 retransmitted
                0 dupsyn
                0 dropped
                14 completed
                0 bucket overflow
                0 cache overflow
                1 reset
                0 stale
                0 aborted
                0 badack
                0 unreach
                0 zone failures
        0 cookies sent
        0 cookies received
udp:
        41738 datagrams received
        0 with incomplete header
        0 with bad data length field
        0 with bad checksum
        0 with no checksum
        8443 dropped due to no socket  
        33104 broadcast/multicast datagrams dropped due to no socket  <-- My Particular Concern
        0 dropped due to full socket buffers
        0 not for hashed pcb
        191 delivered
        254 datagrams output
ip:
        28432403 total packets received
        9 bad header checksums
        0 with size smaller than minimum
        211 with data size < data length
        0 with ip length > max ip packet size
        0 with header length < data size
        0 with data length < header length
        0 with bad options
        0 with incorrect version number
        2585861 fragments received
        0 fragments dropped (dup or out of space)
        57 fragments dropped after timeout
        1292902 packets reassembled ok
        9414002 packets for this host
        2 packets for unknown/unsupported protocol
        17696404 packets forwarded (0 packets fast forwarded)
        16337 packets not forwardable
        0 packets received for unknown multicast group
        0 redirects sent
        15047419 packets sent from this host
        0 packets sent with fabricated ip header
        0 output packets dropped due to no bufs, etc.
        26 output packets discarded due to no route
        97835 output datagrams fragmented
        195670 fragments created
        0 datagrams that can't be fragmented
        0 tunneling packets that can't find gif
        0 datagrams with bad address in header