tutorials/faq: added toc at the top of page

docs/tutorials/faq/main.md

@@ -9,6 +9,86 @@ If you have a question suitable for FAQ and you don't know the answer,
 add it and set the answer to 'TBA', others can read it and give the
 right answer.
 
+## Table Of Contents
+
+- [Frequently Asked Questions](#frequently-asked-questions)
+   * [General](#general)
+      + [What is Kamailio?](#what-is-kamailio)
+      + [Is Kamailio a B2BUA?](#is-kamailio-a-b2bua)
+      + [Can Kamailio be used as SIP redirect server?](#can-kamailio-be-used-as-sip-redirect-server)
+      + [Can Kamailio be used as SIP registrar and location server?](#can-kamailio-be-used-as-sip-registrar-and-location-server)
+      + [Can Kamailio be used as SIP proxy server?](#can-kamailio-be-used-as-sip-proxy-server)
+      + [Can Kamailio be used as SIP load balancer server?](#can-kamailio-be-used-as-sip-load-balancer-server)
+      + [Can I load balance Asterisk or FreeSwitch with Kamailio?](#can-i-load-balance-asterisk-or-freeswitch-with-kamailio)
+      + [Can Kamailio be used as SIP least cost routing server?](#can-kamailio-be-used-as-sip-least-cost-routing-server)
+      + [Is it possible to reload Kamailio configuration file?](#is-it-possible-to-reload-kamailio-configuration-file)
+      + [What is the license of Kamailio?](#what-is-the-license-of-kamailio)
+      + [Can it be installed on Windows?](#can-it-be-installed-on-windows)
+   * [Transport Layers](#transport-layers)
+      + [What transport layer protocols are implemented in Kamailio?](#what-transport-layer-protocols-are-implemented-in-kamailio)
+      + [Does Kamailio have support for WebSockets?](#does-kamailio-have-support-for-websockets)
+      + [Can Kamailio do gatewaying between transport layers?](#can-kamailio-do-gatewaying-between-transport-layers)
+      + [Can Kamailio be used to call from web browsers (webrtc) to classic](#can-kamailio-be-used-to-call-from-web-browsers-webrtc-to-classic)
+               + [Modules](#modules)
+      + [What is a Kamailio module?](#what-is-a-kamailio-module)
+      + [Where are Kamailio modules located?](#where-are-kamailio-modules-located)
+      + [Which modules are compiled by default?](#which-modules-are-compiled-by-default)
+      + [How can I compile and install a module that is excluded by default?](#how-can-i-compile-and-install-a-module-that-is-excluded-by-default)
+      + [I use 'make all', but I can't get the db_mysql.so. How can I get this?](#i-use-make-all-but-i-cant-get-the-db_mysqlso-how-can-i-get-this)
+      + [How to compile only one module?](#how-to-compile-only-one-module)
+   * [SIP Message Processing](#sip-message-processing)
+      + [Why changes made to headers or body are not visible immediately?](#why-changes-made-to-headers-or-body-are-not-visible-immediately)
+      + [Why parts of From/To header appear many times?](#why-parts-of-fromto-header-appear-many-times)
+      + [Why body or other parts of the SIP message appear multiple times?](#why-body-or-other-parts-of-the-sip-message-appear-multiple-times)
+      + [How to set different header values for each destination of a SIP request?](#how-to-set-different-header-values-for-each-destination-of-a-sip-request)
+      + [How to remove a single header field when a header appears multiple times?](#how-to-remove-a-single-header-field-when-a-header-appears-multiple-times)
+      + [Why the SIP requests are replied with "483 Too Many Hops" or "513 Message Too Large"?](#why-the-sip-requests-are-replied-with-483-too-many-hops-or-513-message-too-large)
+      + [I send SIP requests to Kamailio, but nothing happens, why?](#i-send-sip-requests-to-kamailio-but-nothing-happens-why)
+   * [Media Streams](#media-streams)
+      + [Does Kamailio relay media streams?](#does-kamailio-relay-media-streams)
+      + [What codecs are supported by Kamailio?](#what-codecs-are-supported-by-kamailio)
+      + [Can Kamailio be used for video calls?](#can-kamailio-be-used-for-video-calls)
+   * [Getting Started](#getting-started)
+      + [What are the minimum knowledge requirements before starting with Kamailio?](#what-are-the-minimum-knowledge-requirements-before-starting-with-kamailio)
+      + [Any step-by-step guide to install Kamailio?](#any-step-by-step-guide-to-install-kamailio)
+   * [Support](#support)
+      + [Are there public mailing list where one can ask questions about Kamailio?](#are-there-public-mailing-list-where-one-can-ask-questions-about-kamailio)
+      + [What are the rules for posting questions about Kamailio?](#what-are-the-rules-for-posting-questions-about-kamailio)
+      + [Where I can report an issue?](#where-i-can-report-an-issue)
+      + [Where can I buy commercial support?](#where-can-i-buy-commercial-support)
+   * [DNS](#dns)
+      + [Does it have support for ENUM?](#does-it-have-support-for-enum)
+      + [What kind of DNS queries can it do?](#what-kind-of-dns-queries-can-it-do)
+      + [Can it do DNS-based (SRV) load balancing?](#can-it-do-dns-based-srv-load-balancing)
+      + [How to avoid reverse DNS for **src_ip** comparison?](#how-to-avoid-reverse-dns-for-src_ip-comparison)
+   * [Instant Messaging and Presence](#instant-messaging-and-presence)
+      + [Can it route SIP instant messaging requests (page mode, RFC3428)?](#can-it-route-sip-instant-messaging-requests-page-mode-rfc3428)
+      + [Can it store instant messages for offline users and deliver them when the users become online?](#can-it-store-instant-messages-for-offline-users-and-deliver-them-when-the-users-become-online)
+      + [Can it route instant messages using MSRP (RFC4975)?](#can-it-route-instant-messages-using-msrp-rfc4975)
+      + [Can it handle end-to-end presence requests?](#can-it-handle-end-to-end-presence-requests)
+      + [Does it have support for SIP SIMPLE Presence (presence agent model)?](#does-it-have-support-for-sip-simple-presence-presence-agent-model)
+      + [Does it have support for Resource Lists Service?](#does-it-have-support-for-resource-lists-service)
+      + [Can it act as a presence user agent?](#can-it-act-as-a-presence-user-agent)
+      + [Can it handle subscription requests for dialog states (aka, blinking lamps)?](#can-it-handle-subscription-requests-for-dialog-states-aka-blinking-lamps)
+      + [Does it have support for handling XCAP?](#does-it-have-support-for-handling-xcap)
+   * [NAT Traversal](#nat-traversal)
+      + [Can Kamailio be used with phones connecting from behind NAT?](#can-kamailio-be-used-with-phones-connecting-from-behind-nat)
+      + [Can Kamailio be installed behind NAT (e.g., like on Amazon EC2)?](#can-kamailio-be-installed-behind-nat-eg-like-on-amazon-ec2)
+   * [Configuration File Processing](#configuration-file-processing)
+      + [Can I check the configuration files for syntax errors?](#can-i-check-the-configuration-files-for-syntax-errors)
+      + [Do I have to delete the AVPs added in the configuration file for a SIP message?](#do-i-have-to-delete-the-avps-added-in-the-configuration-file-for-a-sip-message)
+      + [What is a pseudo-variable?](#what-is-a-pseudo-variable)
+      + [How to iterate through the items in a comma separated string?](#how-to-iterate-through-the-items-in-a-comma-separated-string)
+      + [How is the function return code evaluated?](#how-is-the-function-return-code-evaluated)
+      + [How is the SIP request retransmission handled?](#how-is-the-sip-request-retransmission-handled)
+   * [Troubleshooting](#troubleshooting)
+      + [I get 'out of memory' errors, what can be done?](#i-get-out-of-memory-errors-what-can-be-done)
+   * [Tools](#tools)
+      + [How to generate HA1 value in command line?](#how-to-generate-ha1-value-in-command-line)
+      + [How to generate HA1B value in command line?](#how-to-generate-ha1b-value-in-command-line)
+      + [Kamctl gives an error regarding opening FIFO file, why?](#kamctl-gives-an-error-regarding-opening-fifo-file-why)
+      + [Kamcmd sometime fails to execute RPC commands with number parameters, why?](#kamcmd-sometime-fails-to-execute-rpc-commands-with-number-parameters-why)
+
 ## General
 
 ### What is Kamailio?