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Mastering FreeSWITCH

You're reading from  Mastering FreeSWITCH

Product type Book
Published in Jul 2016
Publisher Packt
ISBN-13 9781784398880
Pages 300 pages
Edition 1st Edition
Authors (8):
Russell Treleaven Russell Treleaven
Profile icon Russell Treleaven
Seven Du Seven Du
Profile icon Seven Du
Darren Schreiber Darren Schreiber
Profile icon Darren Schreiber
Ken Rice Ken Rice
Profile icon Ken Rice
Mike Jerris Mike Jerris
Profile icon Mike Jerris
Kalyani Kulkarni Kalyani Kulkarni
Profile icon Kalyani Kulkarni
Florent Krieg Florent Krieg
Profile icon Florent Krieg
Charles Bujold Charles Bujold
Profile icon Charles Bujold
View More author details

Table of Contents (21) Chapters close

Mastering FreeSWITCH
About the Authors
About the Reviewers
1. Typical Voice Uses for FreeSWITCH 2. Deploying FreeSWITCH 3. ITSP and Voice Codecs Optimization 4. VoIP Security 5. Audio File and Streaming Formats, Music on Hold, Recording Calls 6. PSTN and TDM 7. WebRTC and Mod_Verto 8. Audio and Video Conferencing 9. Faxing and T38 10. Advanced IVR with Lua 11. Write Your FreeSWITCH Module in C 12. Tracing and Debugging VoIP 13. Homer, Monitoring and Troubleshooting Your Communication Platform Index

FreeSWITCH Products and Services

Another way to see what FreeSWITCH can do is to think in terms of what services it will give its users. Here, too, different technologies and techniques are deployed to cater to different kinds of users, looking for a different set of features.

Business PBX services (hosted and on-premises)

FreeSWITCH's scalability and feature set lends itself naturally to being used as the basis of an extremely powerful business PBX phone system. Successfully deployed in both on-premises environments for small SOHO businesses while scalable to hundreds of users, or utilized as the foundation for hosted PBX services hosting hundreds of thousands of users, the system lends itself naturally to powering these types of solutions.

Out of the box, FreeSWITCH includes basic PBX modules which provide powerful functionalities. These modules include features such as:

  • Ring groups (simultaneous and sequential)

  • Call forwarding

  • Presence

  • Text to speech

  • Call queues

  • Caller ID blacklists

  • Caller ID name delivery

  • Privacy features / anonymous calling

  • CDRs / Call logs

  • Eavesdrop / whisper

  • Voicemail

  • Music on hold (w/ streaming sources)

  • Usage limiting

  • Call pickup / group pickup / call intercept

We could go on further, but this is a good general idea of the building blocks that are provided. Most of these modules can be activated by adding four to six lines of XML to a dial plan configuration file. The power of dial plan combined with modules should not be underestimated - this is powerful stuff with very little work to get it going!

Additional components exist for expanding into:

  • Chat

  • Messaging / SMS

  • HTTP services

Customer demands will sometimes lead to more complex requirements that might not be handled by default modules. However, ready-made building blocks combined with the ability to run your own custom scripts within FreeSWITCH allows for providing quick time to market services even for the most demanding customer base.

Call centers

Any company doing substantial business in any market segment will attest that support is a cornerstone of a business's success. A robust and comprehensive telephony platform is crucial, and FreeSWITCH allows for a configurable, scalable and maintainable solution suitable for call centers of any size.

There is no shortage of flexibility with FreeSWITCH. If your solution requires a custom application, FreeSWITCH provides a host of development options for your call control and routing. Although you are free to use any supported language to "roll your own" solution, FreeSWITCH comes complete with robust call center modules that are being utilized in production environments in literally thousands of deployments all over the world.

Mod call center includes features like:

  • Multi-tenant capability

  • Multiple agent call-distribution strategies, such as :

    • Longest idle agent

    • Round robin agents

    • Agent with least talk time

    • Agent with fewest calls

    • Top-down tier position escalation

  • Time-based scoring escalation strategies like:

    • Total time in system

    • Time in current queue

  • Caller configuration options:

    • Maximum wait time

    • Maximum wait time with no agent

  • Tier rule configuration options:

    • Wait time

    • Skip tiers with no agents

    • Discarded abandoned callers

    • Resumed abandoned callers

  • Recurring announcements with time frequency interval settings

With IVR trees easily integrated into your call center solution and full access to databases for CRM and Knowledge Basis, your ability to create call center applications is almost limitless.

If your requirements do not dictate the granularity of complex configuration options, then there are other options available with an alternative FreeSWITCH module called Mod FIFO. As the name implies, it serves as a first in, first out call-queuing mechanism, with many features and strategies, music on hold, and announcements, that's easy to integrate in custom or third-party applications.

Value added services and games, prizes, and polls

Value Added Services (VAS) are services that offer something on top of pure voice transport.

Some examples include:

  • Real time translations (for example, three-way calls with an interpreter)

  • Party lines (for example, multiple-way calls)

  • Virtual meetings (for example, conferences with or without moderator)

  • Cooperative Environments (for example, audio-video-screensharing-whiteboarding)

  • Fax-on-demand

  • Call screening-whitelisting-blacklisting

  • SMS feed subscriptions (news, traffic, special interests, and so on)

Interactive entertainment and polling is a business that fits perfectly with the ease of programming and integrated messaging capability of FreeSWITCH.

Here are some examples of what has been realized in this field:

  • Radio and TV live talk shows that allow for the public to ask questions and vote on issues, both through voice calls and via SMSs

  • Voice menu trees that ask questions to customers, giving them prizes after a number of correct answers (for example, product awareness and loyalty)

  • Redeem-the-code types of campaigns, where customers or the public can enter a code they found on your documentation or advertising to be awarded a bonus, both via SMSs and voice calls with DTMF

  • Incoming calls statistics (comparative ROI analysis on multiple channel advertising campaigns, for example, what they call the most, the number advertised on radio, TV, Internet, or the one in the press?)

"Class 4" vs "Class 5" operations (and SBCs)

FreeSWITCH is a softswitch. That is, it is a software that handles and interconnects calls, like the manual switchboards where operators answered and distributed calls by moving jacks and cables in old black and white movies.

Softswitches in telco jargon are often categorized as pertaining to a "class," and "Class 4" and "Class 5" are the only two classes you will hear about.

Because those are fuzzy terms, almost marketing terms, you will never find the exact demarcation between Class 4 and Class 5 features and capabilities; a lot of them overlap (anyway, it's mostly the same technology).

An arbitrary rule of thumb can be to use Class 4 when talking about large volume, wholesale switching of call minutes between different carriers, ITSPs, CLECs, with minimal meddling in the audio streams (apart from transcoding, if needed). The term "Class 5" applies to audio or text-based services where end user interaction is in focus and where sophisticated logic is required.

FreeSWITCH is widely used in both contexts.

A typical Class 4 usage would be to interconnect many providers of international voice routes and sell voice minutes based on algorithms about least cost route and/or route quality. Here, the sheer volume of signaling that can be managed per second and the availability of very efficient ways to lookup which route to connect to is of paramount importance. FreeSWITCH with "bypass media", mod_lcr, mod_easyroute, some Lua scripting or custom C code is a perfect platform, easy to use and modify on the fly, without service interruption.

Typical Class 5 usages would be an enterprise or SOHO PBX, a call center system, a fax server with mail2fax and fax2mail, an airport IVR to query flights' arrival times, and so on. Here, FreeSWITCH offers prized features like audio quality (that is, no glitches, distortions, and so on), programmability (how easy it is to implement complex services and business logic), capability of interfacing different media (PSTN to WebRTC, SIP to Skinny, TDM to Skype, SMS to XMPP, and so on) and different audio formats (alaw, ulaw, High Definition Audio, Silk, Siren, G729, Opus, mp3, wav, raw, and so on). Easy integration of Text To Speech and Automatic Speech Recognition, manipulation of audio prompt libraries, and easy ways to gather and interact with user pressed DTMFs are the highlights in FS Class 5 operation.

"SBC" is another very vague marketing buzzword. A Session Border Controller (SBC) is a softswitch that sits on the edge of your own telecommunication network and acts as a point of demarcation and interconnection with the external world. Let's say an SBC is a softswitch with an emphasis on security, NAT traversal, media proxying, network connectivity, manageability, audio transcoding, protocol gatewaying (connecting with different protocols), and protocol adaptation (being the compatibility layer between different "interpretations" of the same protocol). FreeSWITCH excels in those areas, as we have seen before in the two "Classes", while it sports specific SBC features like the most advanced NAT traversal, so smart that it can connect endpoint (that is, user phones) behind residential ADSLs and firewalls, or form a federation between the many international offices of a company, each SBC sitting on different NATed LANs. Also, as security goes, FreeSWITCH is one of the reference implementations for ZRTP media encryption, as well as TLS and SIPS.

WebRTC / web services / Internet-only services

FreeSWITCH's unique modular approach made it an easy choice for extending integration into WebRTC and other web-based services which need a bridge between different types of technologies. As an example, web-based communications are useful but are often hindered by their inability to connect to the rest of the established world, causing adoption to be slow. As an example, users will be reluctant to get rid of their desk phone when their browser-based replacement can't call phone numbers but only other browsers. Best of all, WebRTC support follows the same ease-of-installation and global compatibility standards that FreeSWITCH has become known for in the VoIP world. Users can make calls where one side of the conversation is WebRTC and the other is the PSTN, or WebRTC to SIP and so on. FreeSWITCH does all the hard work of normalizing the audio and signaling services between the two services and bridging any gaps that may exist when connecting from one type of service to another.

Mobile "over-the-top" SIP

As mobile services become more pervasive in the telecommunications industry, mobile network operators have responded by increasing data speeds. In this process, many service providers are now investigating "over-the-top" services which utilize data communication services to transmit and receive voice and video. These services often link to messaging or social applications and provide both real-time, semi real-time, and recorded communication services via data connections. In many cases, the user experience simulates phone technology even though it is not using traditional telephony services provided by the underlying communications service provider. In these cases, there is added complexity for handling such services.

Over-the-top services face a number of challenges, which include:

  • The ability to adapt to rapidly changing network performance characteristics

  • The ability to "hand off" calls as different networks which have better qualities come into range (that is, moving from 3G to 4G or 3G to WiFi)

  • Selecting appropriate codecs which match available capacity and bandwidth

  • Having sufficient buffering and audio stream management strategies to allow for quality communication while being resilient to issues in network consistency

  • Providing feedback to the user to allow her to understand what is happening during these complex shifts

  • The ability to track device configuration and usage information as customers roam to various locations, change devices, and so on.

  • The ability to adapt to networks which block or restrict some kind of traffic

  • Integrating with various types of physical hardware on the user's device

  • Being able to debug issues when it's unclear if they're caused by the device, the mobile network, or the softswitch

Despite the various unique challenges over-the-top apps pose, the attractive promise of cheaper phone calls integrated into social, e-mail, or other methods of communication remains a popular target for many companies.

With these goals and issues in mind, where does FreeSWITCH fit in? It should come as no surprise that FreeSWITCH is a great match for solving these challenges. While less discussed within the FreeSWITCH community, FreeSWITCH contains hidden gems for features such as:

  • Managing a jitter buffer manually, where you can account for non-standard network environments

  • Support for STUN, TURN, ICE, and alternate signaling ports and methods (such as UDP and/or TCP), and the ability to bridge between endpoints using different methods

  • The ability to select codecs on the fly on a per-call basis, which is useful in conjunction with a mechanism to detect current network conditions

  • The ability to handle unexpected events gracefully (such as dropped calls) where strategies can be taken to reconnect a caller automatically without dropping both sides

  • Rich statistics and RTCP feedback implementation providing real-time information to both caller and callee about the quality of the transmission

These are just some of the building blocks that make FreeSWITCH unique when attempting to solve these over-the-top problems. Make no mistake, over-the-top applications are still a challenge. But FreeSWITCH gives you a huge head start in tackling these problems.

Skype to SIP call, seen from FreeSWITCH's remote console

You have been reading a chapter from
Mastering FreeSWITCH
Published in: Jul 2016 Publisher: Packt ISBN-13: 9781784398880
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