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====== Kamailio - Getting Started Guide ======

A collection of guidelines and useful links to smoothen the understanding and
deploying of Kamailio for newbies.

Feel free to add new content here.

The first version of the tutorial was written for Kamailio v4.3.x.

It is recommended that you read first all the content of this tutorial and
then start installing Kamailio, because some more relevant information might be
found later for specific use cases.

===== Prerequisites =====

==== SIP ====

The initial name of the project was SIP Express Router (aka SER) and that says
it all: Kamailio is a SIP router at the core. It means that it works at the
lower layer of SIP packets, routing each and every SIP message that it
receives based on the policies specified in the configuration file.

It is important to understand that it is not a telephony engine at its core, a
VoIP call is seen as a sequence of SIP messages sharing the same attributes
for caller, callee and signaling tokens such as Call-ID, From tag and To tag.

Given the above, a good understanding of SIP is critical to get faster
familiar with Kamailio, especially with its configuration file routing
rules.

Session Initiation Protocol (SIP) is specified by IETF (www.ietf.org), with
the core specification in the RFC 3261:

  * https://tools.ietf.org/html/rfc3261

Many other RFCs add to the core specifications, look at what is published by
the IETF Working Groups for SIP and SIMPLE.

IETF RFC documents are a bit dry to read, with particular language suitable
for technical specifications, therefore trying to learn SIP directly from RFCs
could be not that easy. Fortunately there are plenty of free online resources,
tutorials or blogs, as well as books, that can help understanding SIP faster.

A SIP Introduction tutorial was written by SER/Kamailio developers quite some
time ago. It is available inside source tree of Kamailio, in the folder
doc/sip/. It is docbook xml format, the html version can be read online at:

  * http://www.kamailio.org/docs/tutorials/sip-introduction/

Other online SIP learning resources:

  * [[http://www.siptutorial.net|siptutorial.net]]
  * [[http://www.tutorialspoint.com/session_initiation_protocol/index.htm|tutorialspoint.com]]
  * [[http://www.voip-info.org/wiki/view/SIP|voip-info.org]]

SIP Books:

  * [[http://www.amazon.com/SIP-Beyond-VoIP-Communications-Revolution/dp/0974813001|SIP Beyond VoIP]]
  * [[http://www.amazon.com/Understanding-Session-Initiation-Protocol-Telecommunications-ebook/dp/B003E2UQ8M/|Understanding the Session Initiation Protocol]]
  * [[http://www.amazon.com/SIP-Demystified-Gonzalo-Camarillo-ebook/dp/B000T8OAHC/|SIP Demystified]]
  * [[http://www.amazon.com/Internet-Communications-Using-SIP-Delivering-ebook/dp/B008O5JR20/|Internet Communications Using SIP]]
==== Logical Programming ====

Kamailio configuration file is not just a set of 'parameter=value' line. It
has active components for runtime, named routing blocks. A routing block is a
group of actions that specify what should be done for each SIP message.

The actions are exported by Kamailio core or modules and are like functions
exported by a library. Those actions can be combined in conditional statements
like IF and SWITCH or in loops like WHILE. Modularity is provided by the
ability to execute a routing block from another routing block.

Therefore, understanding logical programming is important as well. Be sure you
are familiar with concepts such as functions, variables, conditions or loops.

IF, SWITCH and WHILE are pretty similar to other imperative languages such as
C, Perl, Python or Java. Even Shell/Bash programming is useful to get into
Kamailio configuration structure.

==== Linux/Unix ====

Being developed for Unix/Linux, managing a Kamailio instance, from
installation to runtime and maintenance involves operations specific for Linux
administration, like running command line applications from terminal,
configure network and firewall to allow sending/receiving SIP and RTP packets,
a.s.o.

Troubleshooting Kamailio and SIP requires knowledge of various tools for
reading and searching log files (e.g., grep, awk), sniffing the network (e.g., sngrep,
ngrep, tcpdump, wireshark). Of course, knowing to work with text editor,
especially the ones for terminal if the server is remote, is quite obvious
(e.g., vim, joe, nano, pico, emacs, etc.).

===== Initial Installation =====

==== From Sources ====

Install current stable version:

  * [[install:4.3.x:git|Install Kamailio v4.3.x From GIT]]

Install development version (master branch):

  * [[install:devel:git|Install Kamailio Devel Version From GIT]]

When installing from sources:

  * configuration files are deployed in: /usr/local/etc/kamailio
  * binary files are deployed in: /usr/local/sbin/
==== Debian ====

Kamailio is part of latest official stable Debian distributions (and its Ubuntu cousin), but might be an older version.

To use most recent Kamailio release, you can use the APT repositories hosted by Kamailio project, see details at:

  * [[packages:debs|KAMAILIO DEBS Repositories]]

Then, the typical way of installing packages can be used:

<code>
apt-get update
apt-get install kamailio
</code>

Various modules are packaged separately, you can search the repository to see what is available:

<code>
apt-cache search kamailio
</code>

Install the other packages of the modules you may need, like mysql or tls modules -- they can be installed with:

<code>
apt-get install kamailio-mysql-modules kamailio-tls-modules
</code>

When installing from deb packages:

  * configuration files are deployed in: /etc/kamailio/
  * binary files are deployed in: /usr/sbin/

==== CentoOS ====

Kamailio RPMs are available for several distributions, such as RedHat
Enterprise, CentOS, OpenSuse and Fedora. For more details, see:

  * [[packages:rpms|KAMAILIO RPMS Repositories]]

You can add them to YUM configuration and then install Kamailio with usual yum
commands:

<code>
yum install kamailio
...
yum install kamailio-mysql-modules kamailio-tls-modules
</code>

When installing from rpm packages:

  * configuration files are deployed in: /etc/kamailio/
  * binary files are deployed in: /usr/sbin/
===== Configuration File =====

==== Overview ====

If you installed from sources, then the configuration file is located at:

  * /usr/local/etc/kamailio/kamailio.cfg

If you installed from packages, then the configuration file is located at:

  * /etc/kamailio/kamailio.cfg

==== Configuration Scripting Language ====

Kamailio uses its own configuration file language. Its structure is described in the Core Cookbook:

  * [[cookbooks:devel:core|Devel Core Cookbook]]
==== Default Configuration File ====

The default configuration file is trying to provide the features for a simple
VoIP (telephony) provider.


  * user authentication
  * IP authorization
  * accounting
  * registrar and location services
  * attacks detection and blocking (anti-flood protection)
  * NAT traversal
  * short dialing on server
  * multiple identities (aliases) for subscribers
  * multi-domain support
  * routing to a PSTN gateway
  * routing to a voicemail server
  * TLS encryption
  * instant messaging (pager mode with MESSAGE requests)
  * presence services

Not all the above features are enabled by default -- read the comments at the
top of **kamailio.cfg** in order to find what tokens must be defined.

=== Enabling User Authentication ===

Initial installation doesn't ask users for authentication.
Enabling that means defining WITH_MYSQL and WITH_AUTH --
that means adding the next two lines after the first line (after the one with
#!KAMAILIO).

<code c>
#!define WITH_MYSQL
#!define WITH_AUTH
</code>

Obviously, for the above to really work, you need to install MySQL server and
create the database required by Kamailio (see **kamdbctl** tool). You need
also to add subscribers (username/password to subscriber database table). You
can use **kamctl** tool for managing subscriber records.


=== Enabling Persistent Location ===

Initial installation doesn't have persistent location enabled, meaning that if
you restart Kamailio, the registration records are lost. If you enable it,
registration records are saved to database and reload at restart.

To enable persistent location records, you have to define WITH_USRLOCDB -- add
the next line in **kamailio.org** after those line you added in the previous
section:

<code c>
#!define WITH_USRLOCDB
</code>

=== Enabling NAT Traversal ===

The default **kamailio.cfg** comes with NAT traversal support, relying on
RTPProxy for RTP relaying. The NAT traversal support has to be enabled by
defining WITH_NAT:

<code c>
#!define WITH_NAT
</code>

You have to install RTPProxy applicationand configure it to use the same
control socket as in **kamailio.cfg** parameter for **rtpproxy** module.

===== Tools =====

==== kamctl ====

Kamctl is part of Kamailio project (in the same source tree) and installed by default.

It has a configuration file named **kamctlrc**, located in the same folder with **kamailio.cfg**. You have to edit it to set your SIP domain, the database engine, username/password/... to connect to database, etc.

This is the tool to manage kamailio from command line, providing lots of operations, such as adding/removing/updating SIP users, controlling the ACL for users, managing the records for LCR or load balancing, viewing registered users and internal statistics, etc.

When needed to interact with Kamailio, it does it via FIFO file created by **mi_fifo** module. Operations to the database are done by connecting directly to the database server.

==== kamdbctl ====

Kamctl is part of Kamailio project (in the same source tree) and installed by default.

It uses the same configuration file like **kamctl**, respectively the **kamctlrc**.

The tool can be used to create and manage the database structure needed by Kamailio, therefore it should be immediately after Kamailio installation, in case you plan to run Kamailio with a database backend.

It is not used for managing the records inside the database tables, just for database structure and access to the database (e.g., granting/revoking access to database server). For managing the records inside database table, **kamctl** is the tool that has to be used.

==== kamcmd ====

Kamctl is part of Kamailio project (in the same source tree) and installed by default.

This is an application that can send RPC commands to Kamailio from command line. It requires that the **ctl** module is loaded by Kamailio.

==== siremis ====

It is a web management interface for Kamailio, written in PHP -- more at:

  * http://www.siremis.org

==== kamcli ====

It is a command line application write in Python, more or less an alternative to **kamctl**. It has a modular architecture, allowing to extend it by writing new plugins.

See more at:

  * https://github.com/asipto/kamcli

===== Typical Use Cases =====

==== VoIP Provider ====

The default **kamailio.cfg** is practically an implementation of simple SIP
operator services. See the section above dedicated to default configuration
file for more details.

==== Load Balancing ====

See dispatcher module:

  * http://kamailio.org/docs/modules/stable/modules/dispatcher.html

==== Least Cost Routing ====

See the modules:

  * http://kamailio.org/docs/modules/stable/modules/lcr.html
  * http://kamailio.org/docs/modules/stable/modules/carrierroute.html
  * http://kamailio.org/docs/modules/stable/modules/drouting.html

==== IMS/VoLTE ====

Look at the modules that have the name prefixed with **ims_** or starting with
**cdp** (the later are for Diameter):

  * http://kamailio.org/docs/modules/stable/

Example of configuration files for different IMS roles (eg., ICSCF, PCSCF,
SCSCF) are available in the source tree, look inside the sub-directory
**examples/**.

==== Instant Messaging and Presence ====

Look at the modules that have the name prefixed with **presence** (presence
server) or **pua** (presence user agent):

  * http://kamailio.org/docs/modules/stable/


==== WebRTC ====

See the module:

  * http://kamailio.org/docs/modules/stable/modules/websocket.html

===== Useful Resources =====

==== Kamailio Books ====

  * [[http://www.asipto.com/sw/kamailio-admin-book/|SIP Routing with Kamailio]]

==== Kamailio Online Tutorials ====

  * [[http://www.asipto.com/pub/kamailio-devel-guide/|Kamailio Devel Tutorial]]
  * [[http://kamailio.org/docs/ser-getting-started/SER-GettingStarted.pdf|SER Getting Started]]

==== Related Open Source Projects ====

Open source projects embedding Kamailio that can help rolling out specific use cases.

  * [[https://www.sipwise.org/products/spce/|sip:provider CE]] - telephony operator platform
  * [[https://github.com/2600hz/kazoo|kazoo]] - cloud PBX platform
  * [[http://www.elastix.org/|Elastix MT]] - multi-tenant PBX system
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