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I have two machines connected to the same LAN and multicasting UDP streams at rate of about 30Mbps. Analyzers often show packet losses on one machine, but never on another.

What could be the reasons for packet losses on particular machine?


I use ubuntu OS. Multicasts passes through router. But when I multicast in LAN with switch, it works fine with zero loss. Packet looses only when router added. Both machines has same hardware, same every piece of hardware.

Multicast from other machine doesn't loose any packets even through router.

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Ummm... Anything? What have you looked at so far? – joeqwerty Aug 1 '14 at 19:37
I see few UDP bad checksums. – UDPLover Aug 1 '14 at 20:09
What operating system/version/distribution/kernel? What server hardware? What NICs? What switches? What software? - You've failed to provide the most basic amount of information here. – ewwhite Aug 1 '14 at 20:25

1 Answer 1

It could be just about anything. It can be CPU speed, I/O latency, interference, or something else. This is just the nature of UDP. If this causes you a problem, you shouldn't be using UDP.

My best guess would be that the router is making the packets more bursty because it is forwarding the packets in chunks, reducing the spacing between them. This increases the chance that a packet towards the end of a burst will find no buffer space available.

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"router is making the packets more bursty". Then why does it not affect the other machine which UDPLover says goes through the router just fine? – Eugene Beresovsky May 13 at 20:53
It's hard to know because the OP only tells us what's the same about the two machines, not what's different. It could, for example, be power management -- the machine with the higher loss may not be able to process a burst of packets as quickly when waking after power management kicks in, so the hardware buffer gets full and the tail packets get dropped. – David Schwartz May 13 at 22:37

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