[Live-devel] Problems with packetdrop in multicast streams.

Johan Winäs johan.winas at i-solutions.se
Sun Mar 6 16:33:42 PST 2005

This is not directly related to live.com, but you might have seen the 
same problem.

We have an application where we recive rtp multicast streams, running on 
windows xp. The problem is that on high loads, we get packet loss.
This is for multicast not a stange problem, the strange part is that I 
have verified that the packets get sent from the switch.....
So the stream is correct on the ethernet line. But I can se that we miss 
packets from the rtp headers in Windows XP.

To verify this, I have made several experiments.
The streams all come thrue one ethernet cabel, in to a cisco 3550 
switch. On this switch I then have 4 computers.
The test setup.
Computer 1 is a Linux server, reciving all 9 streams, total of 27Mbit, 
no packet loss, nice video.
Computer 2 is a Windows XP that recives 4 streams, total of 12Mbit, no 
Computer 3 is a Windows XP that recives 9 streams from the Linux server, 
this is the multicast streams sent via http tcp. No problem with the video.
Computer 4 is a Windows XP that recives 9 streams, total fof 27Mbit, 
packet loss!. Just a few packets, but this gives errors in the video.

So, the only machine that has a problem, is the windows xp machine when 
reciving something above ~14Mbit. I can switch the computers, and the 
problem is the same. The machine trying to view "to much" multicast has 
packet loss. Dont matter with switch port,s or cables either.

The switch dont report any dropped frames or similar, no errors at all. 
On any port. And since the Linux server shows the streams nice, the 
incomming streams must be ok.

We have logged the rtp headers, and there are no packets out of order. 
But I can see that the RTP count jumps a packet or two once in a while.

Anyone having any idés about what this might be?

Already tested xp with no service pack, with sp1 and sp2. sp2 has 
slihtly more packetloss, even that the firewall is turned off.


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