[nmglug] VOIP Asterisk

[John Osmon]

On Tue, May 10, 2011 at 03:39:30PM -0600, J. Marsden DeLapp wrote:
[...]
> How easy is it to setup an Asterisk based PBX? and what do they cost?

With some of the Asterisk centered linux distributions it really isn't
all that hard -- but it will take time to work out how you want to use
such a system.  What are you looking for?
  - an IP based trunking solution that feeds your old PBX?
  - a complete IP based solution with new handsets?
  - some type of hybrid?

Cost-wise -- I've seen 15 - 20 person sites run very well on a dual-core
Atom box that you can buy for around $250.  I've also run my house via
a VM instance on an existing server for $0.

Some things to think about:
  - inbound calls -- do you want to buy cards for the Asterisk box and
    keep using your current provider?  Or would you rather "port" your
    numbers to a VoIP DID provider?
  - outbound calls -- again, physical cards are needed to use
    traditional providers, or you can move to a VoIP provider
    (You can have multiple providers as well, so you can mix and match)
  - call paths -- how many simultaneous calls do you need to be able
    to handle (in and out)

What kind of handsets do you expect/want to use?
  - existing phone system 
  - new IP handsets
  - analog handsets run with ATAs

Each VoIP call is relatively small from a bandwidth perspective -- call
it 90kbps and you're pretty safe.  However, each call will generate 100
packets per second, and some gear can't handle more than 5 or 6
simultaneous calls.  So look at your network:
  - LAN -- generally safe, but not always
  - WAN -- if you want to mix your VoIP and Internet traffic, you're 
    probably going to have to get your service provider to prioritize
    the VoIP traffic -- 

Forget about FAXing over IP.  Under very controlled instances it can
work well -- but most real world applications fail.  Keep a budget for
an analog line if you need FAXing to work.

Overall, don't forget that you can stage things.  I'd do something like:
  1) Build an Asterisk box, and play with some handsets and/or soft
     phones
  2) Get an outbound trunking provider and test calls to the outside
     world -- there are plenty that you can pre-pay $5 - $10 for
     testing.
  3) Get some DIDs from your trunking provider (or another -- it's your 
     choice).  See how inbound calls work
  4) Forward you current linkes to the "new" DIDs you ordered in 3).
  5) When all is working as you want, "port" your DIDs to your DID
     provider

With a plan like the above, you can back out at any time, and keep using
your old system.

Have fun!