Re: listener missing lots of udp broadcasts
Re: listener missing lots of udp broadcasts
- Subject: Re: listener missing lots of udp broadcasts
- From: Jens Alfke <email@hidden>
- Date: Fri, 27 Dec 2013 12:24:51 -0800
Here’s an interesting article I just found:
http://www.wi-fiplanet.com/tutorials/article.php/3433451
It gets rather technical, but one interesting point is that the WiFi protocol has its own packet acknowledgment, so normally even a UDP packet will be resent by the base station if the client doesn’t receive it. But multicast packets are not acknowledged, so they have higher levels of packet loss.
Reading between the lines, I’m guessing that WiFi packets/frames intrinsically have a very high rate of loss, high enough that they had to add an ACK to the protocol to bring it up to the fidelity levels of Ethernet (which does not use acknowledgment.) This would explain why you’re seeing higher than expected levels of loss with multicast.
There’s also a lot of detail in the article about the timing of when multicast packets are sent relative to normal packets. I can’t follow it, but I think it might explain why you sometimes see different rates of packet loss depending on other network traffic.
—Jens
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