Commercial or non-commercial?
Since with Linux we can make very easily an website at our home there are many chances that in VoIP
the success comes in the same way, non-comercially, more easily.
Look at the films for free.
VoIP HowTo
The entire document can be found at http://www.bertolinux.com/voip/english/VoIP-HOWTO.html .
1.1 Introduction
This document explains about VoIP systems. Recent happenings like Internet diffusion at low cost, new integration of dedicated voice compression processors, have changed common user requirements allowing VoIP standards to diffuse. This howto tries to define some basic lines of VoIP architecture.
1.2 Copyright
Copyright (C) 2000,2001, 2002 Roberto Arcomano. This document is free; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This document is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You can get a copy of the GNU GPL at http://www.gnu.org/copyleft/gpl.html .
1.3 Translations
If you want to translate this document you are free, you only have to:
Check that another version of it doesn't already exist at your local LDP.
Maintain all 'Introduction' section (including 'Introduction', 'Copyright', 'Translations', 'Credits').
Warning! You don't have to translate TXT or HTML file, you have to modify LYX file, so that it is possible to convert it all other formats (TXT, HTML, RIFF, etc.): to do that you can use "LyX" application you download from http://www.lyx.org.
No need to ask me to translate! You just have to let me know (if you want) about your translation.
Thank you for your translation!
1.4 Credits
Thanks to Fatamorgana Computers for hardware equipment and experimental opportunity.
Thanks to Linux Documentation Project for publishing and uploading my document in a very quickly fashion.
Thanks to David Price for his support.
5. Requirement
5.1 Hardware requirement
To create a little VoIP system you need the following hardware:
PC 386 or more
Sound card, full duplex capable
a network card or connection to internet or other kind of interface to allow communication between 2 PCs
All that has to be present twice to simulate a standard communication.
The tool above are the minimal requirement for a VoIP connection: next we'll see that we should (and in Internet we must) use more hardware to do the same in a real situation.
Sound card has be full duplex unless we couldn't hear anything while speaking!
As additional you can use hardware cards (see next) able to manage data stream in a compressed format (see Par 4.3).
5.2 Hardware accelerating cards
We can use special cards with hardware accelerating capability. Two of them (and also the only ones directly managed by the Linux kernel at this moment) are the
Quicknet PhoneJack
Quicknet LineJack
VoiceTronix V4PCI
VoiceTronix VPB4
VoiceTronix VPB8L
Quicknet PhoneJack is a sound card that can use standard algorithms to compress audio stream like G723.1 (section 4.3) down to 4.1 Kbps rate.
It can be connected directly to a phone (POTS port) or a couple mic-speaker.
It has a ISA or PCI connector bus.
Quicknet LineJack works like PhoneJack with some addition features (see next).
VoiceTronix V4PCI is a PCI card pretty like Quicknet LineJack but with 4 phone ports.
VoiceTronix VPB4 is a ISA card equivalent to V4PCI.
VoiceTronix VPB8L is a logging card with 8 ports.
For more info see Quicknet web site and VoiceTronix web site.
5.3 Hardware gateway cards
Quicknet LineJack and VoiceTronix cards can be connected to a PSTN line allowing VoIP gateway feature.
Then you'll need a software to manage it (see after).
5.4 Software requirement
We can choose what O.S. to use:
Win9x
Linux
Under Win9x we have Microsoft Netmeeting, Internet Phone, DialPad or others or Internet Switchboard (from Quicknet web site) for Quicknet cards.
Warning!!: Latest Quicknet cards using Swithboard (older version too) NEED to be connected to Internet to get working for managing Microtelco account (not free of charge), so if you plan to remain isolated from Internet you need to install OpenH323 software.
For VoiceTronix cards you can find software at VoiceTronix web site.
Under Linux we have free software GnomeMeeting, a clone of Microsoft Netmeeting, while in console mode we use (also free software) applications from OpenH323 web site: simph323 or ohphone that can also work with Quicknet accelerating hardware.
Attention: all Openh323 source code has to be compiled in a user directory (if not it is necessary to change some environment variable). You are warned that compiling time could be very high and you could need a lot of RAM to make it in a decent time.
5.5 Gateway software
To manage gateway feature (join TCP/IP VoIP to PSTN lines) you need some kind of software like this:
Internet SwitchBoard (only when connected to Internet) for Windows systems also acting as a h323 terminal;
PSTNGw for Linux and Windows systems you download from OpenH323.
5.6 Gatekeeper software
You can download as gatekeeper the Free product Openh323 Gatekeeper (GK) from http://www.gnugk.org .
Version 2.0 of it supports "proxy function" to enabe talking from/to a private network.
5.7 Other software
In addition I report some useful software h323 compliant:
Phonepatch, able to solve problems behind a NAT firewall. It simply allows users (external or internal) calling from a web page (which is reachable from even external and internal users): when web application understands the remote host is ready, it calls (h323) the source telling it all is ok and communication can be established. Phonepatch is a proprietary software (with also a demo version for no more than 3 minutes long conversations) you download from http://www.equival.com/phonepatch .
Same function can be obtained using "Proxy" function of Gatekeeper Gnugk (see before).
8. Communications using PSTN line
8.1 Overview
VoIP becomes very interesting when you start to use PSTN lines to call other people in the world, directly to their home telephone.
8.2 Scenario
A typical application is like that:
Home telephone1 -- (PSTN) -- PC1 -- (Internet) -- PC2 -- (PSTN) -- Home telephone2
Home Telephone1 make a calls to PC1 phone number (using PSTN line, I mean classic telephone line).
PC1 answer to it.
Home telephone1 must tell PC1 what gateway use (PC2 in this case) by giving the IP address (from DTMF keyboard) and/or what number call (in this case Home telephone2).
After that PC1 will start to make an H323 call to PC2, then it will pass Home telephone2 to PC2 to make it call it throught PSTN line.
Home telephone2 answers to call and communication between Home telephone1 and Home telephone2 begins.
8.3 What can be changed in this configuration?
You may use a PBX to select many lines to access many PC1 gateway (for example one to call within your state, one to go accross Europe, and so on...): typically you don't have to change this, 'cause cost is always the same.
You can select (after called your PC1 gateway) every PC2 you want (for example a PC2 living in England to call an English person so that you'd pay only intra-country costs).
So your decision will be taken considering PSTN line costs. In fact what VoIP does is the convert this:
Home Telephone1 --- (PSTN) --- Home Telephone2
PSTN great distance calling cost
into this:
Home Telephone1 --- (PSTN) --- PC1 +
PC2 ---- (PSTN) --- Home Telephone2 =
--------------------------------------
2 PSTN short distance calling costs
To save money you need that:
2 PSTN short distance calling costs < PSTN great distance calling cost.
Typically "short distance calling" refers to a "city cal" while "great distance calling" can be an "intercontinental call"!
Links:
http://www.freewebs.com/voip-now/
http://www.freewebs.com/voip-idea/
http://www.voip-voip.page.tl
http://voip-softphone.blogspot.com
http://voip.haipa.ro
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