VoIP, SIP, and Trixbox

boundlessbazaarServers

Dec 9, 2013 (3 years and 6 months ago)

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PBX




What is a PBX?


(Private Branch Exchange)


A small telephone switch owned
by an organization, which would
allow a reduction in total phone
lines needed by that organization.


Without a PBX, a company would
have to lease a phone line for
each phone.


Historically, switching was done by
hand.


Automated systems replaced old
manually systems



Operators switching calls, Madrid Telecommunications
Museum, Madrid, Spain.

PBX


Asterisk





Software implementation of PBX called
Asterisk

was
created


Allowed all standard PBX features plus some


Created in 1999 by
Digium


Released under the GNU General Public License.


Allowed for the for PCI cards to attach telephones,
telephone lines, T1’s and E1’s.


Many features have been added to it over the years.



VoIP in General





Advantages:


Same phone number anywhere


Easily implement services such as IVR, caller ID, etc. that you
normally pay for


Cost effective


Disadvantages


911 service


Power (not through telephone)


Reliability of internet


Security/encryption

Connecting with VoIP




VoIP phones


Looks like a normal phone, but connects to an Ethernet cable


Has some obvious other internal functions, such as a DHCP client


Sometimes has Power over Ethernet (PoE) capabilities


~$90 and up (PoE more expensive)

Power over Ethernet (
PoE
)



PoE sends power down an ethernet cable


This is somewhat comparable to current POTS technology which
does the same thing


Does not require any changes in the twisted pair


This
does

require special equipment to put power into the cable.


A switch with powered ports (much more expensive than the
equivalent switch without powered ports)


Buy a PoE injector (~$50)


Specified by 802.3af


Other possible uses besides VoIP phones include PoE adapters to
inject where there is a power outlet and take it out at the end to
plug into the device, such as a wireless router where there is no
power present

Connecting with VoIP


Analog Telephone Adaptor (ATA) device


Connects any normal phone to an IP network


~$30.00


Softphones


Software IP phones that you install on a computer


Popular phone is X
-
lite


These require speakers and a microphone.


Purchase Equipment: http://www.ipphone
-
warehouse.com


SIP
(Session Initiation Protocol
)


What is SIP


It is a text based protocol used to set up, maintain, and
tear down multimedia communications such a voice
and video calls over the internet.


RFC 2543, RFC 3261


Runs over
tcp

or udp, typically on port 5060


De facto standard


No security built into it


Ex. Cisco uses proprietary protocol but it can use SIP as
well.




Trixbox


Trixbox is a custom installation of CentOS.


Trixbox comes with a working installation of:


Asterisk


FreePBX administration tool


Other custom administration tools for a machine dedicated to
acting as a PBX


Trixbox CE is completely free and open source.


Trixbox Pro is for commercial call centers, independently
managed and operated.

Trixbox

FreePBX

features


Asterisk does not come with any built in programming, you have
to edit config files first.


FreePBX offers much pre
-
programmed functionality with an
excellent web based interface


Unlimited voicemail boxes


“Follow Me” functionality


Ring groups with call confirmation (so voicemail doesn’t stop the
other phones from ringing)


Unlimited conferences


Music on Hold


Call queues


Much more


LAMPA: Linux Apache MySQL PHP Asterisk

Trunks


To call out, you must add trunks.


Dial out a POTS line using a FXO card (cannot use a normal
modem).


SIP trunks:


You connect your PBX to these places through the SIP protocol,
who will then route your calls out over a POTS line if necessary


They can also give you DID numbers (incoming numbers)


Callcentric
,
voipstreet
, and les.net are 3 examples of such
services


Callcentric

prices: $0.0198/minute


DID number: $1.95/month


ZAP Trunks





Zaptel

compatible devices (interface

drivers)


FXO card

(Foreign Exchange Office)


A card that allows you to plug in a phone line to your
PBX box.


T1 card






Creates a zap channel for each phone line


If you use a SIP trunk the company you connect to will
have to have someway of connecting to phone lines.


Sources




http://www.tech
-
faq.com/pbx.shtml


http://www.packetizer.com/ipmc/sip/papers
/understanding_sip_voip/


http://en.wikipedia.org/wiki/Session_Initiation
_Protocol