[Asterisk-Users] Asterisk phone system plan - for review!

[Mike Ciholas]

Hi all,

I would be most grateful if someone would review my plans for my
new phone system and comment on areas of expected trouble and
advice on what to do better.  Instead of moving our Panasonic
KX-TD1232/TVS200 system (ugh...) to our new location, we've
decided to jump into IP telephony with *.  But we are new to *
(but not Linux), so we're trying to learn as much as we can
before we jump in and drown.  I've got 6 weeks to make this work.

The basic plan is as follows:

1. A T1 for local phone service has 8 "live" channels (and 16
"dead" ones) and uses robbed bit signaling (that is, not a PRI
which was *way* more expensive, why is that?).  A local CLEC
(Cinergy Communications)  can provide the T1 for $75/mo plus
$15/active channel.  I believe this comes with CID w/name plus a
bunch of other features too long to list but probably typical for
this service.  Anything to watch out for in getting a T1?  
Local, long distance, and toll free inbound are provided over the
T1 (5.9c/min for LD and toll free).  I'm not quite ready to jump
to IP dial tone service at this time but I am keeping an eye on
that.

2. The T1 will be terminated on one port of a Digium TE410P, 
$1500.  There seems to be no question this is the right T1 
interface to buy.  There isn't a single Digium product for sale 
on Ebay.  Guess everybody wants to keep theirs!

3. A rack mount PC running * will be in the server room.  It
will have two ethernet interfaces, one for the phones and one for
the internal LAN/internet.  The phones will be on a subnet with
the * box doing the routing between the PC LAN and phone LAN
(which should not be much traffic, right?).  The PC will also
host the voicemail stuff (which I have yet to investigate).  I
have not selected PC hardware in detail, any suggestions?  
Looking at ~$1000 for the PC.

4. The phone LAN will be served by a dedicated ethernet switch.  
I'd love to get one with inline power (Cisco C3524-PWR for
example) but these are expensive relative to garden variety
switches.  We may end up using commodity switches and wall bricks
at each phone until PoE switches become commodity (which they
most certainly will become in 1-2 years).  Do I bite the bullet
and buy a C3524-PWR ($1600 Ebay), do an inline power hub ($?), or
wall bricks ($40/phone?)?  Part of me wants to just take a 48
volt power supply and do some hack in the wiring closet...

5. The desk phones are likely to be Cisco 7940/60 series and run 
SIP.  The phones will have their own LAN jack separate from PC 
traffic.  We are looking at about 25 phones total.

6. For legacy analog phones (fax machine, certain cordless
phones, etc), I will buy an Adtran TA 750 channel bank with FXS
cards (perhaps as many as 24).  Going price seems to be around
$400 for this.  I can add a few FXO ports if I want some POTS
backup lines.  The Adtran would tie into a port of the TE410P.

7. For dial in service, I will buy a Lucent Portmaster 3.  While
this is *serious* overkill for my needs (which are met with 2
analog modems now), it is cheap enough (~$200 Ebay) and it
provides direct to digital modems.  I should be able to get
reasonable connect speeds, perhaps up to 53K (is this true with
T1 robbed bit signaling?).  The PM3 will be tied to one port of
the TE410P Digium card.  If I am feeling gratuitously silly, I
can connect a second T1 to the PM3 and have 48 modems available
(on 8 incoming lines...?).  I know dial in modem service is going
the way of the dodo bird, but having a means for traveling
employees to dial a toll free number and get to the internet is
still very handy!  Presently, our analog modems are passed
through the Panasonic switch which cuts our connect performance
to about 24K (bleah...).  I cannot dedicate an incoming line to 
the modems since they are used sporadically.

8. The power infrastructure is to concentrate as much of the
equipment in the server room and provide everything with UPS
backed power.  Theoretically, during a power failure, all of the
systems will work until the UPS has been depleted.  This assumes
the phones are powered over the LAN cable.  This means we should
have phone service and internet service during power outage.  
UPS recommendations?  I'd like at least 1 hour, and 3 would be
nice!

9. From the software setup, given that the incoming T1 will be
G.711 ulaw (right?), I would probably force everything internal
to be ulaw so the * box has no codec work to do, just shuffling
bits.  I'm not concerned about the bandwidth used on the internal
phone LAN.  This means the TE410P card just shuffles around bytes
between ports/channels (for T1 to channel bank or modems) and *
shuffles bytes between T1 and phone LAN.  Sounds like this is the
simplest setup.  Of course, I don't know what echo canceling will
do to this.  I would guess we would want to hard code that all
calls to/from the modem get no echo canceling.

10. On an experimental basis, it might be nice for certain
employees to be able to have an IP phone at their house via cable
modem.  These phones would talk to the * box via the internet and
they would become "extensions".  I have not research the various
issues of NAT, delay, bandwidth, etc.  It would see we might want
to choose something other than G.711 ulaw for these connections 
to get lower bandwidth.

11. I'd like to get a digital fax receive setup somewhere in this
mess.  Does the PM3 do it?  Otherwise, a fax modem in the * box
connected to one of the FXS lines out of the TA 750 seems doable
but silly.  Seems like we out to be able to decode the fax
directly.  Initial plan is to use existing fax machine on FXS
port and hard copy output, but I hate fax spam.

It's clear my plan is overkill for our immediate needs, but we
expect to grow at this new location by perhaps a factor of 4.  
We can then enable 24 incoming lines on the T1, support
essentially infinite modems, and support 24 FXS devices as
designed.  An additional Adtran TA 750 gets us another 24 FXS
lines if we need them.  If we need more, another TE410P card
would expand us beyond reason.  At some point, we may go IP dial
tone, or perhaps just LD and toll free inbound.

So, do this plan make sense?  Where am I pushing the boundaries 
of the technology?  Where will be my trouble points?

Thanks for everyone's help!

PS: I'm looking for a consultant to "hand hold" me if I get in
trouble with config, setup, etc.  I don't think any on site work
will be needed and we can handle stuff like "check out the latest
CVS and compile it".  If you are in this line of work and really
know your way around * and the equipment listed above, please
send me a note with your areas of expertise, experience, and
rates.

-- 
Mike Ciholas                            (812) 476-2721 voice
CIHOLAS Enterprises                     (812) 476-2881 fax
2626 Kotter Ave, Unit D                 mikec at ciholas.com
Evansville, IN 47715                    http://www.ciholas.com