Re: listener missing lots of udp broadcasts
Re: listener missing lots of udp broadcasts
- Subject: Re: listener missing lots of udp broadcasts
- From: Gordon Apple <email@hidden>
- Date: Fri, 27 Dec 2013 11:29:42 -0500
- Thread-topic: listener missing lots of udp broadcasts
Title: Re: listener missing lots of udp broadcasts
What I want to know is exactly how to do broadcasts over WiFi. What I want is the ability to stream video, possibly screen capture, to a large number of devices, such as a lecture hall full of students. Individual connections are just not practical at this bandwidth and volume of receivers. I was previously told this was not possible.
On 12/26/13 9:28 PM, "Jens Alfke" <email@hidden> wrote:
On Dec 25, 2013, at 11:17 PM, Michael Brian Bentley <email@hidden> wrote:
What is the percent of typical missed packets can I expect from my listener when I have a device broadcasting 100-byte UDP messages at one second intervals over WIFI? I'm seeing above 10%, sometimes well above. I know UDP isn't guaranteed delivery, but what I'm seeing seems excessive.
Way back when, I was told to avoid multicast/broadcast on WiFi.
(a) Broadcast is always bad because it wakes up the network interface of every single device on the LAN whether or not it’s interested. Multicast avoids this because interested clients can listen to that multicast address, and everyone else ignores it.
(b) WiFi base stations handle multicast by dropping the entire networks’ bit-rate way down to the lowest rate, to make delivery more reliable, so every time a multicast packet is sent, all data traffic will slow down for a little while. (Disclaimer: I was told this six or seven years ago, and newer WiFi protocols may have improved this.)
The advice I was given is that it’s often more efficient to send multiple unicast UDP packets, especially if you take into account the throughput of the entire WiFi network.
—Jens
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