[asterisk-biz] How are phone calls routed and who is responsible for what?

[John Schmerold]

The VOIPJet note reminded me of an issue that has been bugging me for 
some time. How are phone calls routed and who is responsible for what?

I understand what happens when I plug www.google.com into my web 
browser, my computer connects to a name server, it contacts its name 
server until the IP address is determined. Then my router contacts its 
router until I'm connected to google.

When it comes to phone calls I'm baffled. When I pick up the handset at 
the house to call my brother's house across the street, they may or may 
not both be in the same switch, handled by the same carrier, delivered 
via the same physical connections.

Who is responsible for this routing and how does one go about protecting 
the route to your phone number.

The point of this exercise is performance and security.
1. Performance
    When we get VOIP service from a supplier, how can we determine their 
ability to perform. On a simple level, we can ping their SIP server. 
Fast, consistent ping may mean good service. However we don't know if we 
just connecting to a sip server that connects to another sip server that 
may or may not have a good connection.

2. Security.
     What if our supplier goes out of business (Remember Enron, Worldcom 
or even NorVergence)? How do we get our number? How long does it take? 
etc etc  Most resellers go through XO or Level 3. Is anyone aware of 
their policies relative to number ports when one of their resellers goes 
broke or refuses to return your number to you?
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