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I'm setting up a LAN comprised of 60 end nodes that are receiving a high volume of UPD datagrams from one master server.

The server sends 60 unique datagrams every 100ms, each datagram is 64 bytes. This means I'm sending 38400 bytes per second.

Each one of the 60 nodes should receive it's unique datagram at roughly the same time, ideally all end nodes get their message within a timespan of <20ms. And this is what I need help with. How should I build this network?

My only real concern here is latency. Security is not an issue since it's a standalone LAN.

What is the best way to build this network and how can I assure this low latency and have all my nodes be roughly in sync?

Thanks

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up vote 4 down vote accepted

At a frequency of 60 packets per 100ms (600 packets per second) you should have no trouble achieving your goals with simple unmanaged gigabit Ethernet switches cascaded (heaped) together, assuming that there's no other traffic on the network. You'll have sub-1ms delivery times of such small frames with even consumer-grade switches provided that yours is the only traffic.

If there is other traffic then you'll start getting into the fun, non-deterministic world that is Ethernet.

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That depends on how latency sensitive it is. I see ping 64byte payload latency of about 300-400ms on cheap hp procurve 2510, but 200-250ms on cisco 2960S. Wouldn't you agree? –  3molo May 30 '12 at 20:11
    
@Evan this will be the only traffic on this network. –  Mattias May 30 '12 at 20:22
    
@3molo that sounds like very high latency, @ –  Mattias May 30 '12 at 20:22
    
@3molo that sounds like very high latency, Evan seems to think sub-1ms delivery time is achievable. When I ping my very small network using a cheap unmanaged Netgear switch I usually see latency under 1ms for ping with 64 bytes payload. Regardless, I'm no networking expert and I'm grateful for you sharing your stats. Does these networks that your pinging have a lot of congestion? Also, what kind of hardware would you recommend in order to lower those delivery times to around 10ms? –  Mattias May 30 '12 at 20:30
    
@3molo: That sounds like latency over a WAN, not a LAN. That's some ungodly huge latency for a LAN. Is it possible you're using a PING utility that returns round trips in microseconds instead of milliseconds? –  Evan Anderson May 30 '12 at 22:05
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