We are considering using a Netburner for a network of 64 nodes. I would like to have a master send small amounts of data <64 bytes to a specific node and then have the node respond with a small message. There will be no other traffic on the network. What kind of latency can I expect?
Thanks,
Andy
UDP latency
Re: UDP latency
It could vary the the number and type of switches and/or routers you have. What is the minimum latency you can live with? You could do a wireshark capture on a couple of devices with your exact network configuration to get a good reading.
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ahbushnell
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Re: UDP latency
I plan to set up tests. I was just wondering if anyone might already have an estimate for latency order of magnitude. i.e. about 1 ms or 100 us or 100ms.
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thomastaranowski
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Re: UDP latency
Definitely less than 1 millisecond for a typical 64 node 100Mb/s network. It's hard to make any other sort of determination without details.
The key questions are:
* How many packets are in flight to the master and slave at any give time. The netburner needs to empty it's Ethernet receive queue, and if there's other Ethernet frames in front, it delays reception. For your case, unless you're streaming alot of data, this isn't an issue.
* How are the nodes wired? If you have them all on a single segment and they are all busy talking at the same moment, you would have alot of contention, and your latency will be much more than 1ms, due to the CSMA/CD backoff.
If you have a switched network, you'll be in alot better shape, so long as all the slaves don't respond back to the master at the same instant. If your thinking of having the master broadcast a beacon, then have all the slaves respond, you might have some packet loss on the receive side unless you bump the number of your master's ethernet receive buffers so that you can queue up all 64 frames.
The key questions are:
* How many packets are in flight to the master and slave at any give time. The netburner needs to empty it's Ethernet receive queue, and if there's other Ethernet frames in front, it delays reception. For your case, unless you're streaming alot of data, this isn't an issue.
* How are the nodes wired? If you have them all on a single segment and they are all busy talking at the same moment, you would have alot of contention, and your latency will be much more than 1ms, due to the CSMA/CD backoff.
If you have a switched network, you'll be in alot better shape, so long as all the slaves don't respond back to the master at the same instant. If your thinking of having the master broadcast a beacon, then have all the slaves respond, you might have some packet loss on the receive side unless you bump the number of your master's ethernet receive buffers so that you can queue up all 64 frames.
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ahbushnell
- Posts: 25
- Joined: Thu Apr 24, 2008 7:45 pm
Re: UDP latency
[quote="thomastaranowski"]Definitely less than 1 millisecond for a typical 64 node 100Mb/s network. It's hard to make any other sort of determination without details.
That's what I was looking for. I plan to have the master send information to one device get a replay and then move on to the next. If I can do that on the order of 1 ms I'm in FAT city.
Thanks
That's what I was looking for. I plan to have the master send information to one device get a replay and then move on to the next. If I can do that on the order of 1 ms I'm in FAT city.
Thanks