The issue is wrt the onboard Intel NICs which keeps dropping multicast packets:
NIC Name: Intel 82574L GigE Eth Controller
Driver Date: 9/29/2010
Driver Version: 22.214.171.124
BIOS Rev: 2.0a
Intel westmere CPUs: X5680 @3.33GHz (6 Core- 2 CPUs installed for total of 12 cores).
Operating System Details:
Windows 7 (64bit)
Memory: 8GB Reg. ECC DDR3
We have a network where we connect multicast senders to a DLINK Websmart DGS-1224T switch. We also connect our supermicro unit with the above NIC to the same switch. The unit acts as consumer of multicast packets for e.g VLC player running on the unit.
We see packet losses on a multicast session when following condition happens:
1. Start 2 stream (5Mbps each) from the sender to some multicast address such as 126.96.36.199:1231 & 188.8.131.52:1232
2. Start a consumer (e.g. VLC player) instance on the unit in question and tune to the mutlicast 184.108.40.206:1231. This session will experience a lot of packet losses.
3. Start another consumer (e.e VLC player) isntance on the unit and tune it to the other multicast 220.127.116.11:1232. Now the packet losses on the first session (18.104.22.168) disappears and the stream runs fine, in fact both streams run fine without any packet losses.
4. Stop any consumer and the reamining running consumer starts to experience packet losses again.
A lot of debugging at our end indicated that if there are "m" multicast streams on the network, and if the swtich is not doing a true multicast but is just flooding all the packets on all the ports on the switch, then to have loss free multicast streams on the unit we have to run _exactly_ "m" number of consumers on the unit. This is a very strange behavior as the NIC should be able to handle all the packets which are getting sent to the NIC with out any errors as the NIC is a gigabit ethernet card and the total multicast traffic is only at 10Mbps.
When we added another NIC ( a Broadcomm gigabit NIC) on the unit (by removing the graphics card and using that PICe slot) we did not see this behavior. The NIC was able to handle the traffic flood without any problem and the consumers on the unit did not encounter any multicast packet losses.
We also noticed that if we set the speed and duplex settings on the NIC and the port on the switch to be at "100MbpsFull Duplex", this behavior of packet drops is not observed. However, we need to use the 1GbpsFull duplex on the NIC for our product.
Another observation wrt to the Intel onboard NIC is that, if the multicast is set as 22.214.171.124:1231 & 126.96.36.199:1232 (same mutlicast destination IP, but different port) then the multicast sessions work just fine without any packet losses.
Please let us know how to fix this issue.
PS: Even though I have mentioned in the above text that the switch is a DLINK switch, this issue was reproduced on other switches from Alcatel-Lucent and Cisco switches at one of our client sites.