Looking to learn a new skill or a new language? Educating yourself is now as easy as visiting a website. Here are 9 that are great for online learning.
Source: 9 Websites Where You Can Learn Anything For Free (Make Tech Easier)
Looking to learn a new skill or a new language? Educating yourself is now as easy as visiting a website. Here are 9 that are great for online learning.
Source: 9 Websites Where You Can Learn Anything For Free (Make Tech Easier)
As you probably know, Scribd is a popular document-hosting website, and if someone wanted to share a PDF file online, chances are they would upload it on Scribd. However, its interface and restrictive features, like paywall and required sign-up to download files, have been making a lot of people unhappy. Since Scribd is modifying its business model to become a “Netflix for books,” maybe it’s time to consider some Scribd alternatives. Luckily, there are more than enough to choose from. Some are simple and offer only basic file upload, while others provide a complete PDF hosting and reading experience.
Full article here:
5 Scribd Alternatives to Host Your PDF Files (Make Tech Easier)
If you have ever wondered why there are so few females in computer-related fields, it’s probably because of experiences such as the one that this woman’s daughter went through. What makes it worse is some of the idiotic comments posted under the article. Some of those comments really make us wonder about the future of humanity. Fortunately, there are many other comments that indicate that people do understand that this is a real problem. We just wish there were more of them!
To my daughter’s high school programming teacher (Usenix)
Oh, and for those that focused on the comments about Visual Basic, that is not what the article is about. If that’s all you got out of it, you might want to read it again!
The FreeSWITCH Cookbook is the second book from Packt Publishing on the subject of FreeSWITCH, which in my opinion may someday soon be the “telephony software engine” that replaces Asterisk in popularity. I’ve previously reviewed the earlier book, FreeSWITCH 1.0.6, and this book builds on that one. If you know nothing at all about FreeSWITCH, you’ll probably want to start with the earlier book, because it gives you all the basics. The publisher was kind enough to send me a complementary copy of the new book for review purposes.
This book, as the name implies, is a “cookbook” in that it gives “recipes” for how to do certain tasks. Just as an actual cookbook presupposes certain knowledge (that you know how to operate an oven; the difference between certain measuring units, etc.) this book tends to start with the assumption that you already have a grasp of how to set up FreeSWITCH, but you may need examples of the configuration necessary to perform certain tasks. And, that’s what this book gives you. The idea, I think, is that if even one of the “recipes” saves you a couple of hours of head-scratching and trying to figure out how to do something, then that justifies the cost of the book.
Normally in this type of review I would list the chapters, but in the case of this book you’ll probably want to know what’s in each chapter. So, here is the complete Table of Contents from the Packt Publishing web site:
As you can see, the order progresses from the basics (setting up your extensions, and inbound and outbound routing) to the sort of things you might want to do in a more full-featured PBX. Chapter 4 in particular will be of interest to many developers. I’ll quote from the introduction to that chapter:
One of the most powerful features of FreeSWITCH is the ability to connect to it and control it from an external resource. This is made possible by the powerful FreeSWITCH event system and its connection to the outside world: the event socket. The event socket interface is a simple TCP-based connection that programmers can use to connect to the inner-workings of a FreeSWITCH server. Furthermore, the FreeSWITCH developers have also created the Event Socket Library (ESL), which is an abstraction layer to make programming with the event socket a lot simpler. The following languages are supported by ESL:
Keep in mind that the ESL is only an abstraction library—you can connect to the event socket with any socket-capable application, including telnet!
The tips in this chapter will focus most of their attention on using the event socket for some common use cases. The last tip, though, will introduce a particularly interesting way to connect to FreeSWITCH externally without using the event socket, namely, using the built-in web server that is enabled when you install mod_xml_rpc. Regardless of how you wish to control FreeSWITCH, it is highly recommended that you read the first recipe in this chapter, Getting familiar with the fs_cli interface, as this will serve you well in all aspects of working with FreeSWITCH.
This, of course, is somewhat analogous to controlling Asterisk via Asterisk Gateway Interface programming, but it appears that you get more functionality in FreeSWITCH, and more languages are supported.
I have said on many occasions that I am not a programmer, so in one sense I’m not exactly the target audience for this book. However, I know just enough about coding to be able to appreciate when a book lays out examples in a clear, easy-to-understand manner, with enough comments for you to “get” what the author is trying to explain to you. Personally, if I could just get over my hurdle of not fully grasping XML (which is actually strange, because I have no problem understanding basic HTML, which is very similar), I think that this book would be a lot more useful to me in understanding how to do things in FreeSWITCH. I sort of “get” Asterisk dialplans a little bit, but for some odd reason XML is not nearly as understandable to me. I guess everyone’s mind works a little differently. If you work with FreeSWITCH and you don’t share my mental block with regard to XML, you are really going to like this book. In terms of layout and readability, I think it’s one of the best titles I’ve seen from Packt.
One thing in particular I like about this book is that they don’t just give you the XML dialplan (although the XML is included), but the authors then explain to you how it works. In addition, in many cases they also give you additional related information, such as tweaks you can make to the XML to perform slightly different functions or otherwise modify the behavior, and links to additional resources you made need. So, you are not just viewing XML samples and then left on your own to puzzle out how they work!
In fact, I really only have one criticism of the book — it’s too short! It’s only 134 pages from opening material to the index at the end. But I’ll balance that by saying this — I’ve seen too many books that have a high page count, but a high percentage of the book is “filler”, much like the low-grade ground beef you buy at some supermarkets. With this book, other than a few obligatory opening pages that tell you a bit about the authors and others involved with the book, it’s solid content. No history of something or other, no long personal ramblings by the authors, etc. — just the “recipes” for doing the various things you might want to do in FreeSWITCH, and then the explanations as to how they work and other useful and relevant content. You have to ask yourself the question, “Will this book save me time?” (almost certainly, if you are doing any of the things covered in the chapters of this book) and “How much is my time worth?”, and “Can I learn something from this book that would be useful to me?” (if you developing a project using FreeSWITCH, I can’t imagine how you wouldn’t).
My personal hope is that those who write, or who may be considering writing the next generation of GUI configuration programs for FreeSWITCH will get this book. It basically shows you how to do everything you need to do to create a working PBX, and for those that are programmers, Chapter 4 is where the real magic is revealed. That said, I would highly recommend this book for anyone attempting to develop a project using FreeSWITCH!
You can read a sample chapter here (PDF format).
FreeSWITCH Cookbook by Anthony Minessale, Michael S Collins, Darren Schreiber, Raymond Chandler (Amazon affiliate link)
Addendum: Just a bit more from the publisher’s site:
What you will learn from this book
In case you’ve never heard of FreeSWITCH, it is a “telephony software engine”, which means it’s in the same category as Asterisk. Over the years I’ve noticed that some Asterisk users have become frustrated with Asterisk due to unfixed bugs and design flaws that mean that the software doesn’t always work as it should. So, for quite some time, I’d hoped that a viable alternative to Asterisk might emerge, if only to keep the Asterisk developers on their toes. Competition between software projects tends to be a healthy thing, and from what I’ve read in this book, it appears that FreeSWITCH just may be the software product that eventually replaces Asterisk as the #1 open source telephony software engine.
Before I begin, as is my custom with such reviews, let’s start with a quick overview of what’s in each chapter (for the complete Table of Contents, see the Packt Publishing web site):
There are also two appendices:
The Packt Publishing web site also has this to say about the book:
What you will learn from this book :
- Set up a basic system to make and receive phone calls, make calls between extensions, and utilize basic PBX functionality
- Avoid common implementation mistakes and deploy various features of this telephony system with best practices and expert tips
- Perform routine maintenance for smooth running and troubleshoot the system when things are not going right
- Apply regular expressions to unlock unique and powerful call routing scenarios
- Call your own application(s) when particular events occur and control FreeSWITCH using the powerful Event Socket
- Set up multi-party conferencing facilities for your system
- Interact with callers, gather information, and route calls to the appropriate recipient using the automated, built-in XML IVR (Interactive Voice Response) engine
- Create a flexible dialplan, and allow third-party tools to be quickly and easily created using dialplan parsers other than the default XML Dialplan
- Park multiple calls in a FIFO queue and unpark them in the order in which they were received, using the mod_fifo module
- Record an entire phone call or session using the call recording feature
- Create advanced call control applications with the Lua scripting language
- Take a peek into the vibrant online community and history of FreeSWITCH
This book is a step-by-step tutorial with clear instructions and screenshots to guide you through the creation of a complete, cost-effective telephony system. You will start with installation, walk through the different features, and see how to manage and maintain the system.
Who this book is written for
If you are an IT professional or enthusiast who is interested in quickly getting a powerful telephony system up and running using the free and open source application FreeSWITCH, this book is for you. Telephony experience will be helpful, but is not required.
Now, here are my impressions. Please bear in mind that I did not actually attempt to build a working FreeSWITCH installation (I would need yet another spare computer to do that), but I certainly feel as though I could after reading this book. One thing that is somewhat uncommon about this book is that the author of the software is also one of the authors of the book. Too often, when you see a book written about a piece of software, the writer doesn’t fully understand the software and therefore makes guesses and assumptions about how it works, that may lead to problems down the road if you follow their advice. When the software author collaborates on the book, that’s far less likely to happen, and indeed, at no point in this book did I get the feeling that the author was struggling to understand the subject. I will even go so far as to say that this is one of the best written technical books I have read in a long time.
The biggest complaint I had about this book — and it is a very minor one — is that it could have benefited from another proofreader. Occasionally I’d see an obvious error that the proofreader should have caught — nothing major, and nothing I couldn’t figure out with about two seconds of thought, with one exception. On page 91 of the book, it appears to me as though there is some missing text at the bottom of the page. It’s discussing making a test call to Music on Hold and then, suddenly and jarringly, it jumps into a time of day example. I think the disconnect occurs in middle of a sentence: “In our example, call the debug output is as follows:” The sentence as written does not make sense to me, and it appears a block of text (perhaps a large one) may have been omitted at this point. But that is the only place in the book where I encountered an error of that magnitude. I have submitted the error to Packt Publishing and I’m hoping they will figure out what was supposed to go there and place it in the errata section of their web site.
One other point I will make about a software author writing a book on his own creation is that I think sometimes, it’s difficult for the author to correctly envision how end users will want to use the software. As an example, virtually all the dialplan examples in this book are in XML. There may be advantages to using XML, but it’s not going to be very familiar to someone coming from an Asterisk background, and I might have wished for a few non-XML examples. On pages 158-159, the author notes that,
There is a common misconception that the FreeSWITCH Dialplan is based on, and requires, XML. That is simply not true. If you prefer flat files, you could use them to store your Dialplan configuration. If you prefer YAML, you could use that, too. You just need to load the correct C-based Dialplan module to interpret your stored logic for the particular type of configuration file you want FreeSWITCH to utilize.
This aside, the most common (and currently, the most robust) Dialplan processing mechanism in FreeSWITCH is still the XML-based Dialplan module. Most Dialplan examples that are shipped with FreeSWITCH, or those scattered on the Web are in XML, therefore, they will remain the focus of this chapter. …..
Indeed, there is even an Asterisk dialplan module, albeit with limited capabilities. From page 199:
If you are used to the Asterisk Dialplan, some basic functionality is provided by the Asterisk Dialplan module, although it is not nearly as feature-rich as the XML engine. You can process contexts and route calls to phones using the Asterisk Dialplan. This module, again, is more of a sample on how to build an alternate Dialplan processing module and should not be utilized as a full, feature-rich Dialplan system.
Yet you won’t find examples using flat files, YAML, or Asterisk Dialplan in the book. However, the XML examples were clearly written and easy to understand, so I don’t think that there would be a steep learning curve to start writing dialplans in XML, assuming you are a proficient enough coder to write dialplans in the first place. And, I suspect that XML would be easier for a new user to pick up than any of the other options.
I mention the above to emphasize two points: FreeSWITCH is different from Asterisk. If you are thinking about moving from Asterisk to FreeSWITCH, you need this book to get you up to speed on the differences. And second, FreeSWITCH is both more capable than Asterisk, and arguably easier to use, once you get used to the differences (or if you have no prior experience with similar software). FreeSWITCH appears to have been designed from the ground up to avoid the issues that have plagued Asterisk, particularly those that cause Asterisk to fall to its knees under heavy load or heavy call volumes. Even if you’re a long-time Asterisk user, you may want to get this book just to see what you’re missing. You might decide that it’s worth your effort to set up a test system using FreeSWITCH, to help you understand how much better the next generation of telephony software engines can be.
One other point, in case you are reading this review several months after I wrote it — the author notes this in the preface:
At the time of this writing this book, the FreeSWITCH developers were putting the finishing touches on FreeSWITCH version 1.2. While the examples presented in this book were specifically tested with version 1.0.6, they have also been confirmed to work with the latest FreeSWITCH development versions that form the basis of version 1.2. Do not be concerned about the fact that this material does not cover version 1.2—it certainly does. The FreeSWITCH user interface is very stable between versions; therefore, this text will be applicable for years to come.
There will no doubt be some of you who are reading this that wonder if there are any Web GUI “front ends” (dialplan and configuration file generators) for FreeSWITCH. Indeed there are, and they are covered in Chapter 10, which briefly explains the differences between WikiPBX, FreePBX v3, FusionPBX, and 2600hz. Even if you plan on using a Web GUI, there may be times when you find the need to write a bit of custom code, and in that case having this book available would definitely be helpful to you.
One other thing I personally found interesting in this book was Appendix B, “The History Of FreeSWITCH.” This explains how FreeSWITCH came to be, and along the way offers further explanation on how it is different from Asterisk and why the developers felt the need to start a new project. What I think I found most interesting (and perhaps unfortunate, depending on your point of view) is that FreeSWITCH could have been the basis for Asterisk version 2, had only the Asterisk developers reacted positively to the idea. I see this sort of thing happen occasionally in the open source community, where the lead developers of a project start to develop an attitude that does not encourage outside contributions (or, they treat contributions or suggestions for improvement as if they were piles of steaming dog poo on their doorstep). Perhaps this should serve as a cautionary tale to such developers that your project can always be replaced by something better, if you do not encourage contributions to your own project from those not currently in your “inner circle” of developers.
As you may know if you have read my previous reviews, it’s rare that I get wildly enthusiastic about a book. In this case I’ll make an exception, because overall the book is that well-written (my comments above notwithstanding). If you have any interest at all in using FreeSWITCH, or are even just curious about it, you really should buy this book. It’s available in both traditional softcover dead-tree format, and as a DRM free Adobe PDF eBook, and there’s even a package deal if you want both formats. Don’t forget that you can view a sample chapter (PDF format) prior to purchase. EDIT: Also, there is an online article by the book’s authors entitled FreeSWITCH: Utilizing the Built-in IVR Engine.
FreeSWITCH 1.0.6 by Anthony Minessale, Darren Schreiber, Michael S. Collins (Amazon affiliate link)
Related: Review of FreeSWITCH Cookbook by Anthony Minessale, Michael S Collins, Darren Schreiber, Raymond Chandler (Packt Publishing)
I have previously reviewed the title, “Review of OpenVPN: Building and Integrating Virtual Private Networks by Markus Feilner“, and this is the updated and expanded version of that book. The publisher says that all examples in the book work with version 2.0.9 and 2.1 of OpenVPN. Since the original book was released in 2006, it was definitely due for an update!
Here’s what the publisher wants you to know about the book (my comments will follow):
OpenVPN is a powerful, open source SSL VPN application. It can secure site-to-site connections, WiFi, and enterprise-scale remote connections. While being a full-featured VPN solution, OpenVPN is easy to use and does not suffer from the complexity that characterizes other IPsec VPN implementations. It uses the secure and stable TLS/SSL mechanisms for authentication and encryption. This book is an easy introduction to this popular VPN application. After introducing the basics of security and VPN, it moves on to cover using OpenVPN, from installing it on various platforms, through configuring basic tunnels, to more advanced features, such as using the application with firewalls, routers, proxy servers, and OpenVPN scripting.
This is a practical guide to using OpenVPN for building both basic and complex Virtual Private Networks. It will save you a lot of time and help you build better VPNs that suit your requirements. While providing only necessary theoretical background, the book takes a practical approach, presenting plenty of examples. It starts with an introduction into the theory of VPNs and OpenVPN, followed by a simple installation example on almost every available platform. After a concise and ordered list of OpenVPN’s parameters, we dive into connecting several machines in a safe way. The last third of the book deals with professional and high-end scenarios, and also mobile integration. After having read the whole book and followed and understood all the examples, you will be an expert in VPN, Security, and especially in OpenVPN Technology. This book was written for version 2.0.9 of OpenVPN, but all examples have been tested and run smoothly on version 2.1 too.
Read the full Table of Contents for Beginning OpenVPN 2.0.9
What you will learn from this book
This book is an easy introduction to OpenVPN. While providing only necessary theoretical background, it takes a practical approach, presenting plenty of examples. It is written in a friendly style making this complex topic easy and a joy to read. It first covers basic VPN concepts, then moves to introduce basic OpenVPN configurations, before covering advanced uses of OpenVPN.
Who this book is written for
This book is for both experienced and new OpenVPN users. If you are interested in security and privacy in the internet, or want to have your notebook or mobile phone connected safely to the internet, the server in your company, or at home, you will find this book useful. It presumes basic knowledge of Linux, but no knowledge of VPNs is required.
Now back to my mini-review. If you read my original review (which explains why I think a VPN can be an important part of securing private VoIP networks, among other uses), you know that I found Mr. Feilner’s original book quite helpful in giving me a grasp on VPNs, a subject I’d known very little about prior to that point. There were a few things I thought could have been covered better, though, so I was interested to see if those things had been addressed in this updated edition.
As I had more or less noted, the author seemed to slightly prefer SuSE Linux over other versions of Linux, and the Shorewall firewall over other Linux firewall solutions, and (in my opinion) the new book still uses more pages than are really necessary talking about how to set up and configure Shorewall, but at least now the authors do provide some minimal information about the far more popular iptables firewall tool (a little over three pages). It would have been nice to see a more in-depth treatment of this subject, because sometimes setting up iptables correctly is one key to getting your VPN to work as you want it to, particularly if you need or want to do anything more complicated than a simple VPN tunnel. It’s a minor nit, to be sure, because there’s plenty of information on the web about how to set up and configure iptables, but I personally would have given that topic more than three pages.
Then I discovered they’d made one addition that I really wanted to see: A totally new chapter on OpenVPN GUI tools, and in particular, a section on Webmin’s OpenVPN plugin. My disappointment again was that this was not a more exhaustive treatment of the subject. Actually, it’s little more than a mention that the plugin exists, and a few screenshots. Granted that this was more than appeared in the original volume, and just informing readers of the existence of that plugin is no small thing, but when I did my series on Setting up an OpenVPN tunnel using a CentOS-based system as the server and a router flashed with Tomato firmware as the client, it took me two parts to explain how to configure the Webmin plugin. That same chapter also talks about some client GUI’s for Linux, but doesn’t spend more than a page or two on any of them.
I’m not really faulting the authors here — it’s very apparent that they write about what they know, and they definitely know their stuff when it comes to OpenVPN, whereas they may not be quite as familiar with Webmin or iptables. That said, Windows users should find all the information they need to set up an OpenVPN tunnel and then some, and Linux newbies get enough information to at least point them in the right direction. As for Mac users, the coverage there is about the same as in the previous edition, which is to say that there’s about three pages on how to install Tunnelblick. However, much of the information in the book is not OS specific, and those with some experience with Linux or OS X should have no trouble at all following along.
On a positive note, there are many examples and screenshots in the book, and in this one the screenshots are actually readable (well, I did need my reading glasses for a few of them, but then I’m getting to the point where I need my reading glasses to read the cooking directions on a frozen dinner!). And, the authors’ writing style is clear and easy to understand. Also, there’s a totally new (albeit relatively short) chapter on Mobile Security, which may be of interest to some of the “road warriors” out there.
So, my recommendation is this: If you read Markus Feilner’s previous book on OpenVPN and liked it, you’re almost certainly going to want to read this one, just to get up to date. If you didn’t read the previous edition but just want to get up to speed on OpenVPN, this really is one of the better books on the subject, provided that you understand that at times you may have to supplement the book with a bit of additional research on the Web, particularly if you are running OS X or Linux as your operating system (but at least you’ll have a much better handle on topics for additional research).
The reason this is a mini-review and not a full review is because due to personal/family issues I haven’t had time to do much more than skim through the new book, rather than give it a complete read as I normally prefer to do. But since Packt Publishing kindly sent me the book over a month ago, I feel as though it’s a disservice to both them and to the readers of this blog to delay mentioning it any longer. Despite my comments about the paucity of additional pages on the particular topics I’d hoped to read more about, this is still a great book for those who need to set up and secure an OpenVPN tunnel, particularly if you’re just starting out and know next to nothing about VPNs and/or OpenVPN.
Beginning OpenVPN 2.0.9 by Markus Feilner, Norbert Graf (Amazon affiliate link)
This article was originally published in December, 2009.
Regular readers of this blog may recall that I recently reviewed another Packt Publishing book, FreePBX 2.5 Powerful Telephony Solutions by Alex Robar, and that my review was generally positive. However, I have wondered for a while if there was going to be any serious competition for Asterisk and FreePBX that would also be open source, and freely available to anyone that cares to download it. Well, this book discusses one contender – sipXecs by SIPfoundry. You can look over their web site to get some idea of what sipXecs is, but in one respect it’s along the same lines as FreePBX, in that it provides a web-based GUI that allows you to do all the work of configuring your phone system from any web browser. The book is called Building Enterprise Ready Telephony Systems with sipXecs 4.0 by Michael W. Picher.
I’ve never personally so much as laid eyes upon a working sipXecs installation, so this isn’t going to be a review of sipXecs per se. But I suppose some are wondering what the difference is between sipXecs and FreePBX. The impression I got from reading this book is that the two have some differences in features, and even where there is feature overlap, there are differences in the way those features are implemented. If you are just counting features, FreePBX probably offers more, and many of those features have more configuration options. FreePBX would probably work very well in a home or small office. sipXecs, on the other hand, seems to have been designed by folks with experience in networking and larger business installations. If you were trying to link several branches of a medium-sized to large corporation together, and it’s crucial to have 100% uptime (or as close to that figure as possible), sipXecs might be a better choice (at least until someone high in the corporate food chain demands a feature it doesn’t offer). And if you’re a networking professional, you might find sipXecs more appealing. This is definitely NOT to say that sipXecs could not be used in a home or small office setting, nor that FreePBX could not be used in a large corporation for that matter, just that each may fill a particular niche better than the other.
So I will concentrate on the book itself, and I’ll let the publisher have the first word. Here is how they describe this book:
A clear and concise approach to building a communications system for any organization with the open source sipX Enterprise Communications Server
Open source telephony systems are making big waves in the communications industry. Moving your organization from a lab environment to production system can seem like a daunting and inherently risky proposition. Building Enterprise Ready Telephony Systems with sipXecs delivers proven techniques for deploying reliable and robust communications systems.
Building Enterprise Ready Telephony Systems with sipXecs provides a guiding hand in planning, building and migrating a corporate communications system to the open source sipXecs SIP PBX platform. Following this step-by-step guide makes normally complex tasks, such as migrating your existing communication system to VOIP and deploying phones, easy. Imagine how good you’ll feel when you have a complete, enterprise ready telephony system at work in your business.
Planning a communications system for any size of network can seem an overwhelmingly complicated task. Deploying a robust and reliable communications system may seem even harder. This book will start by helping you understand the nuts and bolts of a Voice over IP Telephony system. The base knowledge gained is then built upon with system design and product selection. Soon you will be able to implement, utilize and maintain a communications system with sipXecs. Many screen-shots and diagrams help to illustrate and make simple what can otherwise be a complex undertaking. It’s easy to build an enterprise ready telephony system when you follow this helpful, straightforward guide.
What you will learn from this book
• Understand the complexities of an IP Telephony and Voice over IP network
• Build a clear process for migrating existing phone systems to an IP based system
• Deliver a solid foundation for any IP based phone system
• Quickly and easily get a sipXecs open source PBX running
• Deploy phones quickly and easily.
• Utilize Internet Telephony Service Providers to reduce monthly telephony bills
• Develop training materials to help successfully teach your users how to use the system
• Leverage sipXecs Automatic Call Distribution Queues to handle basic Call Center needs
• Operate and Maintain a reliable communications platform
This book was written to be a step by step approach to building a communications system for any organization. Care was taken to clearly illustrate with diagrams and screen shots all of the steps and concepts along the way. [Emphasis added – I’ll have more to say on that point!]
Who this book is written for
This book is written for network engineers who have been asked to deploy and maintain communications systems for their organizations.
And here’s the chapter list:
Chapter 1: Introduction to Telephony Concepts and sipXecs
Chapter 2: System Planning and Equipment Selection
Chapter 3: Installing sipXecs
Chapter 4: Configuring Users
Chapter 5: Configuring Phones in sipXecs
Chapter 6: Connecting to the World with sipXecs
Chapter 7: Configuring sipXecs Server Features
Chapter 8: Using sipXecs—The User Perspective
Chapter 9: Configuring Advanced sipXecs Features
Chapter 10: Utilizing the sipXecs ACD Service
Chapter 11: Maintenance and Security
See the Table of Contents page to get a more detailed chapter breakdown.
Now, when I review a book, the thing I am looking at is whether the author accomplishes what he or she set out to do. In this case, the intent of the book is to instruct someone in how to set up a working sipXecs PBX. So, I look at whether the author seems to have a good grasp of his subject matter, and whether he can communicate his knowledge to the reader in a clear and understandable manner. A third consideration is whether the book is a good value for the money. Technical books often aren’t inexpensive, so I tend to mark them down if I perceive that there’s a lot of “filler” material in the book.
It’s difficult for me to decide how to rate this book. Does the author understand his subject matter? Yes, it certainly appears that he does. Does he effectively communicate it? Yes, the book was an easy read — I really didn’t feel like I was in “over my head” at any point in the book. Could you set up a working sipXecs phone system after reading this book? I think I could, but I can’t speak for anyone else. In fact, in many ways, this was one of the clearest and most understandable technical books I’ve read.
You sense a “but” coming, don’t you?
Well, there is, and it’s a big one. Did you notice above where the publisher said that “Care was taken to clearly illustrate with diagrams and screen shots all of the steps and concepts along the way”? Well, the book definitely contains screenshots — a LOT of screenshots. And normally, that would be very good thing, because as the saying goes, a picture is worth a thousand words. A screenshot would not add value to a book only in the case where it was useless “filler” material, and it’s pretty apparent that none of the screenshots in this book were intended to just be “filler.”
But, for a screenshot to be useful and not “filler”, it has to be readable. And in that regard, this book has a serious problem. If you buy the hardcopy edition of the book, I’d strongly urge you to also buy a good magnifying glass, because you’re going to need it to get anything out of those screenshots, unless perhaps you have perfect vision. Apparently the author (or whoever took the screenshots) has a widescreen monitor, and was running their web browser in full screen (or at least full width) mode. As a result, most of the text in the screenshots borders on microscopic, and some of the smaller print is unreadable (by me, anyway). When you take those extra-wide screenshots and reduce them to about five inches in width on a printed page, you need very good eyes (or good glasses) to make out the text. After trying to decipher the details in those screenshots for a while, I started to get a headache!
At first I thought maybe it was my eyes going bad — I am getting older, after all — but then I opened up some of the other books I have in my collection, including other Packt Publishing books, and none of them suffer from this problem. Frankly, if I were the publisher I’d stop the presses on this book immediately, and not let another copy go out the door until all the screenshots were re-done, but then that’s just me.
Now, that said, the book is not totally without value. I think that perhaps the author just might have realized he had a problem, because in many cases he repeats in the text most of what’s in the screenshot (at least the portion to which he’s calling your attention), so not being able to actually read the screenshot isn’t always such a loss — but unfortunately, it also relegates the screenshots more toward the category of “filler.”
So, would I recommend this book? Yes, for two classes of readers in particular:
If it weren’t for the screenshot issue, I’d be giving this book very high marks. The focus of the book is deployment in a business setting, and the author takes you through the steps for planning and implementing the system, whether you are replacing an existing PBX or starting from scratch. Having some knowledge of computer networking would be helpful, but as I noted, I’m no networking expert and yet I didn’t feel totally lost. In fact, if you know telephone systems but don’t know all that much about networking, you’ll find that just about everything you really need to know is explained, but without going into extraneous detail. You get the information you need to get the job done, but if you want to become a networking guru, you’ll need some other book for that.
I’m just really sorry that the bad screenshots marred an otherwise fine book, but I have to call ’em as I see ’em, and in my opinion they really are that bad. Whether that would matter to you is something only you can decide. I should mention that I was provided a hardcopy edition of the book for review, but Packt also offers an e-book edition in Adobe PDF format on their web site, and if you are comfortable reading e-books, I’d definitely go that route with this book, because most PDF readers will let you magnify sections of a page. So, the nearly unreadable screenshots might actually be very readable in the e-book edition. Also, if you do go the e-book route, be sure to scroll down the page and look for the offer, “Buy this eBook with FreePBX 2.5 Powerful Telephony Solutions eBook and get 50% discount on both. Just enter sip40xecs in the ‘Promotion Code’.” Seems like a good deal, especially if you’re wanting to compare FreePBX and sipXecs.
Building Enterprise Ready Telephony Systems with sipXecs 4.0 by Michael W. Picher (Packt Publishing link) (Amazon affiliate link)
This article was originally published in September, 2009.
FreePBX 2.5 Powerful Telephony Solutions by Alex Robar (Packt Publishing) explains how to set up, configure, and maintain a powerful VoIP PBX using FreePBX. For those not familiar with FreePBX, it’s a “front end” for the Asterisk PBX software. Asterisk can be thought of as the “engine” that runs the PBX, but FreePBX is the user interface. It basically saves you the effort of writing Asterisk configuration files and dial plans by hand. Instead, you enter all the requisite information in FreePBX’s web-based GUI, and then when you apply the configuration changes (by clicking an orange bar at the top of the screen), FreePBX (re)writes the Asterisk dial plan and configuration files on the fly. This means that making significant changes to the call flow within the PBX, or adding new extensions or trunks, can be accomplished in a matter of seconds or minutes. It also means that you can have a fully functional PBX up and running in a few hours (perhaps even less than an hour if you’re exceptionally quick and it’s not your first installation).
As I like to do in reviews, before I begin I’ll give you a thumbnail description of what’s in each chapter (condensed from information on the Packt Publishing web site):
There are also four appendices:
I’m coming from a slightly different place in my review of this book than with other books I’ve reviewed. In this case I’ve already very familiar with the subject material, having helped set up and configure a FreePBX system that belongs to another member of my family. I was a bit afraid that because I’m already so familiar with the subject, I’d find several glaring errors or oversights. Happily, that proved not to be the case – this book is a good, solid treatment of setting up and configuring a FreePBX system. In fact, the title should have been “How to set up and maintain a FreePBX system”, because that’s exactly what this book explains.
The first thing that impressed me about this book is that there was no “filler” material. Very often, with technical books, the author really only has about 75 to 100 pages of actual material, but because publishers like to publish books that have somewhere around a couple hundred pages, the author will flesh out the book with a history of the software, a profile of the developers, comparisons with competing products, and (if they are really desperate for material) a history of the Internet. 🙂 That is not the case here. After a very short preface, the author jumps right into the subject material, starting with how to install FreePBX and then continuing through subsequent chapters with virtually everything you need to know about configuration. While not every chapter may be meaningful to every reader (personally, I’ve never had the need to record a call — so far — but it’s nice to know that FreePBX can do it), the book at least touches on all the major features of FreePBX.
If I had to make one criticism of the book, it’s that in some places it reads a little bit too much like an instruction manual. And that’s not necessarily a bad thing, because FreePBX has badly needed a good manual to assist first time users in getting it set up and running. This is the manual that should have come with FreePBX. That said, the author really doesn’t touch some of the problems frequently encountered by new users. For example, in the discussion of SIP endpoints, he notes that “SIP can be problematic when traversing firewalls and other NAT devices” and that “Configuration can be particularly troublesome if both the endpoint and the FreePBX system are behind their own firewalls” (p. 44). And there he leaves the reader hanging. There is no discussion of how to overcome the problem, nor is there a pointer to the FreePBX FAQ’s or How-To’s anywhere in the book. While many readers may not encounter this issue, a fair number will, and it would have been nice if they’d been thrown a bone, if only in the form of a pointer to the FreePBX page that addresses the issue.
In my opinion, perhaps the biggest omission is in the discussion of Trunk setup in Chapter 4. This was really the only chapter in which I got the distinct feeling that the author may have been in just a bit over his head, and perhaps did not fully grasp the subject matter covered in the chapter. Not only are there errors in his examples of dial pattern usage (p. 81 – under no circumstances would you use two pipe characters in the same dial pattern, as is shown for some of the toll-free number examples), but when discussing IAX2 and SIP trunks (p. 83), only cursory information is given about how to populate the PEER details and USER details fields. Nor is it explained that with many commercial VoIP providers, the USER context and USER details fields are not used, and should be left blank. However, in the author’s defense, I suspect that I understand why this may have happened — there probably aren’t ten people on the face of the earth that can give you a full explanation of all the options that could possibly be used in the trunk PEER and USER details fields, and when and how each option should be used. Trunk configuration is probably the most difficult part of setting up FreePBX, precisely because there’s no definitive guide on how to do it correctly. In most cases, I suspect that finding the correct options to use with any particular provider is a matter of trial and error — you make educated guesses about which options might be needed and how they should be configured, and if you find a combination that works, perhaps you post it so that others can use it. Some of the known working trunk configuration settings appear in Appendix D of the book, but there are more sample configurations available at the FreePBX web site.
I only mention this because I was hopeful that maybe someone would finally provide a really good how-to on setting up FreePBX trunks, since this is something that almost always confounds new users, and even causes experienced users to get a few (more) gray hairs on occasion. Had I been writing such a book, and had I really understood the subject, I might have given several pages to the subject of trunk configuration in general, and PEER and USER details in particular, not just a few cursory paragraphs. On the other hand, most users will probably seek out a tested and working trunk configuration for whatever provider(s) they use. It’s not as though there isn’t any online help on the subject, but — and this is another minor criticism — for some reason the book barely mentions the availability of online help (for example, unless I missed it there is no specific mention of the FreePBX How-Tos that address several of the issues encountered by new users). This is why I say that at times the book reads like an instruction manual — it gives you all the basics, but seldom touches the “edge cases”, the little quirks and problems that may be encountered by a significant subset of users, but not by all.
However, I don’t want to leave you with the idea that this book is simply a rehash of information that could be found online — even if that were the case, it presents that information in a logical manner that is easily understandable by the reader. But, many essential functions of maintaining a FreePBX system happen outside of the FreePBX interface. For example, you cannot update your operating system or Asterisk from within the FreePBX GUI, but the book explains how to do both. Chapters 10 and 11 (on System Protection, Backup and Restoration, and Security and Access Control) deal with functions that are at least partially handled outside of FreePBX. In some instances the author provides useful shell scripts that automate particular tasks (for example, deleting old, outdated backups to avoid filling up the hard drive). And in many cases, the book does explain things that new users need to know, but might not know that they need to know — for example, the explanation of Codecs and the penalty involved (both in terms of system performance and call latency) in transcoding between codecs.
Anyway, the bottom line is this: Let’s say your boss wants you to set up a new office phone system using Asterisk, and gives you a couple of weeks to do it. If you have no prior experience with Asterisk, you will almost certainly want to use FreePBX (the alternative is writing dial plans and configuration files by hand, and trust me, you don’t want to do that unless you are the sort of person who enjoys writing source code for major projects, and even then you probably don’t want to do it if you’re under any sort of time deadline). And if you’re going to use FreePBX, and you don’t want to spend hours and even days ferreting out information on the Internet, you need this book. Get your boss to buy it (there’s even an e-book version if you need it right now), then just follow the instructions, chapter by chapter. In a few days time, you’ll be well on your way to becoming a FreePBX expert. That’s partly because FreePBX is so easy to use in the first place, but also because the book tells you pretty much everything you need to know, in a very understandable manner. If you get stuck, help is available at the FreePBX web site and at other various locations on the Internet.
If you are a long-time FreePBX user, you may find that you already know much of what’s in this book, but then again it might surprise you how much can still be learned. For example, I found several good suggestions for adding additional security to a FreePBX system in Chapter 11 of the book — and let’s face it, many of us are probably a bit lax about securing our systems to the greatest possible extent (and that could be a very costly mistake).
One other point I should make — as the title of the book implies, it deals with a particular version of FreePBX, namely version 2.5. Of course, as so often happens with a book about software, the ink is barely dry on the paper when a new version comes out. FreePBX 2.6 has already been offered as a release candidate, and beta versions of FreePBX 3.0 are being made available. From a user’s standpoint, version 2.6 will be nearly identical to 2.5 – there may be a few added options and such, but for the most part they are not things that you would need to worry about, or that would detract from the accuracy of this book. However, FreePBX 3.0 will be a major rewrite, but it’s only available in an early beta version, and unless you are an experimenter that wants to be on the bleeding edge, you don’t want it yet. Whenever you do move to FreePBX version 3.0 — and I’d be very surprised if a full release version is much closer than a year away — much of what you’ve learned about FreePBX 2.5 and subsequent versions will still be applicable (and also, I suspect that people will be using FreePBX 2.x versions for quite some time to come).
FreePBX 2.5 Powerful Telephony Solutions by Alex Robar (Amazon affiliate link)
Before I start, let me give you a brief description of what’s in each chapter (this is taken directly from the Packt Publishing web site):
Although this may seem like a strange subject for this blog, I have recently become interested in the concept of Virtual Private Networks (VPN) because of the increasing number of attacks on Asterisk-based system based on spoof SIP credentials. SIP, the most popular protocol for VoIP, is an inherently insecure protocol – it relies on password protection only, and on most Asterisk boxes and in many VoIP devices and software products, the password is stored in plain text. On many systems, the user name is the same as the extension number, so all a potential intruder has to do is start a brute-force attack guessing passwords. The use of strong passwords along with the use of software like Fail2Ban (with iptables) can help minimize the exposure, but in the end it’s still only password protection.
Therefore, my feeling is that it would be much better to restrict extensions to access from within the local network (wherever possible), using the permit/deny fields in FreePBX or some similar mechanism, and then “tunnel” remote extensions through a secure VPN, so they appear to be on the local network. The VPN could do the heavy lifting for security (even making the actual calls secure, although that wasn’t a priority in my situation). My problem was that I knew next to nothing about VPN’s, and most of the pages on the Web seemed to assume at least some prior knowledge. I needed something that would take me from zero knowledge to VPN guru. Unfortunately, at my age it’s a case of “the spirit is willing but the brain is a bit weak”, so I realized that the “guru” part might not come very quickly (just as a comparison, I’ve been playing with FreePBX since back in the Asterisk@Home days, and there’s still a lot I don’t understand, but for the first year or so I felt totally lost).
Since the folks at Packt Publishing were willing to send me a review copy of OpenVPN: Building and Integrating Virtual Private Networks, I decided to see if I could actually learn anything from the book. The first thing you need to know is that there are many types of VPN’s out there, and each will only communicate with its own kind, as it were. The problem with most other tunnels is that they are either not all that secure, or contain proprietary code, or are incredibly complicated to set up and use (or some combination of the above). OpenVPN has several advantages, perhaps the biggest being that it’s open source (so you can, if you are so inclined, examine the code and make sure there are no “backdoors” built in), that it can be as secure as you want it to be (and it’s not that difficult to make it very secure), and that it doesn’t rely on a third-party service over which you have no control (like one VPN application that touts itself as “zero-configuration”). So of all the VPN methods out there, OpenVPN seemed like a logical choice.
Now, having said that, the book covers its subject in a very logical manner. Advanced readers (those already familiar with the principles behind VPNs) might find the introductory material in the first chapters a bit tedious, but believe me, it was just what I needed to help me get a grasp on the subject. As you go further through the book, there are many actual examples, first showing how to set up a working VPN tunnel, then how to add additional security, and finally how to troubleshoot connections. If you are brand new at this, like me, you will probably find that you learn a great deal from the first chapters but find the latter chapters (especially Chapter 10) a bit beyond your comprehension at first. However, the person who has some networking or VPN experience under their belt may think the first chapters a bit elementary, but will find the real meat they are looking for in the latter parts of the book. Either way, I guarantee you will come away with a greater comprehension of the subject.
The book shows how to install OpenVPN on several platforms (Windows, Mac OS X using Tunnelblick, FreeBSD, and SuSE, Debian, and Redhat/Fedora based versions of Linux), but it seems like some platforms are better covered than others. A disproportionate number of examples and screenshots seem to be based on a Windows installation, whereas the Mac gets very little coverage. Because there are so many variations of Linux, the coverage there is mixed, although it seems like SuSE and Debian are better covered than Fedora-based versions, which was just a little bit disappointing because most Asterisk and FreePBX systems are based on CentOS, which is a Fedora-based OS. But most of the information in this book is not OS specific, so I didn’t have any real problem following along.
The biggest disappointment for me was in Chapter 8, where the book covers the use of Webmin, but primarily as an aid to administration of the Shorewall firewall. Many Asterisk/FreePBX systems don’t use Shorewall, but instead use iptables (if they have a firewall on the Asterisk server at all). But what was really disappointing was that there was no mention of, nor instructions for the use of the OpenVPN + CA module for Webmin (page is in Italian, but here is a description in English). I can only guess that because the book was first released in May, 2006 and version 1.0 of the Webmin module had only just been released in January of that same year, the author perhaps hadn’t had an opportunity to work with the module before the final draft of the book was submitted to the publisher. I hope that if this book is ever updated and republished, there will be consideration given to adding a chapter on the use of the Webmin module to set up and administer OpenVPN. In the meantime, you can find instructions for using the OpenVPN + CA module in The ‘Point and Click’ Home VPN HowTo Guide.
That said, I felt I learned a great deal from this book. I was able to set up an OpenVPN server (using the Webmin module, but the book definitely helped me understand the purpose of the various options, and when I checked the configuration file that the module generated I was able to spot a couple of things that weren’t the way they should be for my setup and was able to change them) and the Windows client. It all worked beautifully.
My project now, when I have absolutely nothing else to do, is trying to get the OpenVPN client running on an Asus WL-520gu router that has the DD-WRT firmware installed (I inherited this project from someone else who couldn’t do it). So far this has proven to be a tough nut to crack – although it should be easy because (if you get the right version of DD-WRT) there is a built-in OpenVPN client with a handy configuration page, it just doesn’t seem to work “out of the box” – and from what I’m reading on the ‘net, for every one person who says they’ve got it working, there are about twenty others who have become incredibly frustrated by the process (example here – note that the original poster says he got it working, but that’s followed by about 16 pages of comments, mostly by people who just can’t seem to get it to go). It’s a bit strange because the Windows client will work perfectly (indicating it’s not an issue with the server) but the firmware client in DD-WRT just doesn’t seem to work. If I ever get it figured out, I’ll try to post what I did in this blog, but so far I’ve had no luck. That, however, is not the fault of the book – in my opinion it’s the fault of the writers of the DD-WRT firmware, who apparently included a half-baked OpenVPN client interface in the firmware (I know, it’s free software so I can’t really complain, but one does wish that they’d taken a bit more care to make sure it worked).
After having read the book, I do feel fairly confident that if I should throw in the towel and decide to dump DD-WRT and install a different firmware on the router (I’m thinking about trying the Tomato firmware with USB support) I would be able to install an OpenVPN client from scratch and make it work. Probably the main reason I haven’t wanted to do that is because I very much prefer using a GUI to do things, and would like to try to make the OpenVPN GUI in DD-WRT work (even if it requires a little help), but so far that doesn’t seem to be panning out.
But I digress a bit – anyway, if you are wanting to learn about OpenVPN, whether or not you are a rank beginner you will benefit from this book. The numerous examples and screenshots make it almost impossible to fail to get an OpenVPN tunnel up and running (providing you’re not using a questionable firmware client). And, as I said above, the book is laid out in a very logical progression, so I really didn’t feel totally lost at any point (as so often happens when I try to read technical books). Especially in the case where your boss suddenly decides he needs VPN tunneling capability, and wants you to have one up and running in a very short timeframe, this would be the book to get!
OpenVPN: Building and Integrating Virtual Private Networks by Markus Feilner (Amazon affiliate link)
EDIT: This book has been updated and expanded under a new title — see Mini-review of Beginning OpenVPN 2.0.9 by Markus Feilner and Norbert Graf (Packt Publishing)