[rescue] VOIP

Al Potter apotter at spankingnuns.com
Sun Oct 12 19:10:45 CDT 2003

patrick at zill.net said:
> Except 802.11 was never intended for this kind of use, and voice
> quality is 
> GOING to suck, particularly when you roam.

> Well, I don't think that it would particularly be a problem in most
> cases.  With overhead, etc. the most you can get on 11mbps 802.11 is
> about 3mbps full-duplex .  But you might only need 128kbps or less for
> good voice quality.  Vonage does it with less than 90kbps; as long as
> your latency is not too bad (say under 95ms ping times) you would be
> OK.

It's not the throughput, or the average latency, it's the latency that piles 
up during the roaming operations.  Particularly with the new WPA or 802.11i 
security, the 4-way handshake that sets up the keying during association and 
reassociation introduces more latency than the voice weenies are happy with.

FWIW, I'm hosting an IEEE 802.11i meeting starting Tuesday......

And I'm not generalizing, I'm paraphrasing results from a lab test which 
showed the timings to be problemating under ideal lab conditions.  Real 
world will only be worse.


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