voip vs. your isp

[jack-rp9/bkPP+cDYtjvyW6yDsg at public.gmane.org (Jack Coats)]

After working for a company that deals in VOIP almost exclusively, 
bandwidth is not the real problem for VOIP, it is the latency.  If 'on 
average' you packets are 'quick' getting there, makes for good 
bandwidth.  But getting there in order, reliably is the issue.  Some of 
the VOIP compression algorithm's really help reduce the bandwidth to 
pretty much a non-issue, but long latency kills you.

Since most IP providers are not focused on low latency connections, just 
'fast' connections, one of the few ways many VOIP providers have found 
to make it work is to 'significantly over subscribe bandwidth'.  If you 
need a T1 of bandwidth, you may have to get at least a T3 to make the T1 
of voice fully usable.  Unless you can get a IP provider that focuses on 
low latency connectivity or you manage your own network end to end, it 
is almost impossible to guarantee any kind of high quality VOIP service.

It doesn't have to be that way.  But from experience, most IP providers 
do not give priority to VOIP flagged packets, so even flagging them is a 
waste of time.  And if even one of the routers 'accidentally drops' the 
flag, all bets are off.

If industry starts recognizing the priority flags for VOIP or other 
truly time sensitive packets, there are people/companies that will turn 
it on for all their packets, making it a moot point again.

Yes, I am cynical, but experience earned my my gray hair.