Wireless data propagation time

[George]

I need a non-continuous low speed (<5 kbps) wireless data connection to my laptop from a desktop computer. But I'm having difficulty confirming that the data propagation time will be what I need: under 300 msec one-way. Thecircuit length is short, within the same city.

Does this propagation time require a dialup circuit-switched connection like an old-style voice circuit on which we never hear delay? Or does it haveto be packet-switched nowadays and, if so, is there a way to keep the datapropagation time low?

I'm assuming I'll use a dongle on the laptop and subscribe to a pay-as-you-go data plan.

 

[Ecnerwal]

You can ping the other machine to get an idea of the timing, but
there's no worst-case maximum for wireless.

Or packet-based wires/fibers, which is what wireless connects to.

like, at a Windows command prompt,

ping 66.117.140.16

gives me times like 10, 11, 12, 17 milliseconds, from San Francisco to
Berkeley.

And I (at the moment) get 23-42 ms from the US East coast to John's
company on the West coast. Depending what else is going on, delay can
exceed (though it rarely does) 1000ms over half a mile.

Best if you can work with the realities of how networks work (can be,
often are quick - can be slow, can be lost completely.)

At the moment, a device on my local net about 1/4 mile away has times
between 7 and 84ms - based on that particular pair of samples (8 packets
each), it can be twice as slow to go 1/4 mile as to go 2500 miles.
Welcome to networks 101.

Your likely options are to get away from a hard 300ms limit, or to
figure some way to verify transit times when you are doing "whatever it
is you need to do" and be able to re-do it if the time slips while you
are doing it. Most of the time it will probably work, but guaranteeing
it is not really in the cards via normal networking channels.

 

[Jasen Betts]

I need a non-continuous low speed (<5 kbps) wireless data connection to my laptop from a desktop computer. But I'm having difficulty confirming that the data propagation time will be what I need: under 300 msec one-way. The circuit length is short, within the same city.

Does this propagation time require a dialup circuit-switched connection like an old-style voice circuit on which we never hear delay? Or does it have to be packet-switched nowadays and, if so, is there a way to keep the data propagation time low?

I'm assuming I'll use a dongle on the laptop and subscribe to a pay-as-you-go data plan.

large buffers are the enemy of latency, they do unfortunately improve
other throughput benchmarks so many equipment makers include them.

also look into the QOS bits.

Can you afford some packet loss?, UDP has lower latency by eschewing error recovery.

a GSM voice circuit is 9.6Kbps, and low latency, but lost packets are
not retried. I've heard echo on GSM circuits, but I'm not sure how much
latency it represents.

 

[whit3rd]

I need a non-continuous low speed (<5 kbps) wireless data connection to my laptop from a desktop computer. But I'm having difficulty confirming that the data propagation time will be what I need: under 300 msec one-way. The circuit length is short, within the same city.

This, in general, is not possible with IP protocols. There is no isochronous layer, no
way to ensure a clear channel for your requirement. The video folk have workarounds,
and are trying to come up with a successor to TCP/IP, but the basic scheme is to tolerate
delays and not to control them.

This reminds me of an incident a few months ago, when a mis-configured router, somewhere
in China, was taking much of the worlds internet traffic (not delivering, just advertising
that it was 'free' and capable of delivering). People noticed the delays.

<http://arstechnica.com/security/2010/11/how-china-swallowed-15-of-net-traffic-for-18-minutes/>

 

[josephkk]

I need a non-continuous low speed (<5 kbps) wireless data connection to my laptop from a desktop computer. But I'm having difficulty confirming that the data propagation time will be what I need: under 300 msec one-way. The circuit length is short, within the same city.

Does this propagation time require a dialup circuit-switched connection like an old-style voice circuit on which we never hear delay? Or does ithave to be packet-switched nowadays and, if so, is there a way to keep the data propagation time low?

I'm assuming I'll use a dongle on the laptop and subscribe to a pay-as-you-go data plan.

That really depends on how critical limited latency is. If it is absolute
hard line limit just use circuit switched technology.

?-)