adventures of a VoIP / SIP / IMS trainer & contractor|info@rzfeeser.com

A basic Asterisk v1.8 extensions.conf configuration

This is a basic extensions.conf (the Asterisk dialplan) configuration for Asterisk v1.8. As you can see, only two lines are actually necessary in extensions.conf for the SIP user agents defined in sip.conf to be able to call one another.

If you’re confused, than examine this dialplan in conjunction with my previous blog post on configuring a basic sip.conf in Asterisk 1.8. It may also enhance your understanding of Asterisk to examine the script I posted that complies any version of Asterisk in Ubutnu.

The default location for extension.conf on an Ubuntu 10.04 and 12.04 system is:
/etc/asterisk/extensions.conf
The configuration file is commented for maximum clarity. The active code […]

Rotary phone – Kellogg K-500 decomposed

For the past few months, I’ve been regularly lecturing on the architecture of the IP Multimedia Subsystem, and VoLTE access. Therefore, I thought it fitting to take a step back and explore some classic telephony.

Western Electric produced the WE 500 in 1949, a design that was Bell’s standard issue deskphone from 1950 to 1984 (when the Bell divestiture into ‘Baby Bells took place’).

The following is a decomposed view of the a Kellogg 500 (K-500) from 1958, which was produced by Kellogg / International Telephone and Telegraph (ITT) under licensed permission from Western Electric. The K-500 is identical to the […]

China’s Golden Shield project (Great Firewall) explained

I taught a lesson on SIP and the DNS, and had the following question asked by a student, “How is China handling their DNS requests? Is that how they are able to filter the net?”.

It was a tad off topic, but a great question. I had a feeling that China’s Golden Shield project (The Great Firewall), was a tad more involved than just controlling zone files, so I deferred the question till the next day, until I could research a proper answer. Here’s a brief summary of what I found.

Why did China feel a need for the Golden Shield Project?

The Golden Shield […]

How to calculate necessary bandwidth for a VoIP network

When I teach SIP, H.248, Cisco, or Avaya training courses, I’m often asked how to calculate necessary bandwidth for a VoIP network. I’m actually headed out the door to teach a SIP Essentials class this week, and seeing as I am anticipating this question, I thought I might post some helpful resources on the subject.

Essentially, it’s a question of the type of payload (codec you’ve selected), the sample period (how many samples per packet), and then taking into consideration the IP/UDP/RTP header information (generally, 40 octets), and then transmission overhead (generally, Ethernet 18 octets). After calculating bandwidth required for one call, […]

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    Introducing Cisco Voice and Unified Communications Administration v8.0 (ICOMM 640-461)

Introducing Cisco Voice and Unified Communications Administration v8.0 (ICOMM 640-461)

A few days ago, I passed the ‘CCNA Voice’, or as it is properly named, Introducing Cisco Voice and Unified Communications Administration v8.0 (ICOMM 640-461) exam, with a 95.3%. Both Cisco and Pearson Vue make it quite clear, that discussing the contents of the exam will result in an instant revocation of your certification, so I won’t be doing that in this post. I will, however, recommend that you take the ICOMM if you’re a communications jockey looking for a way to get a little more life out of your CCNA, or are looking to enhance your understanding of Cisco Unified Communications […]

Don’t let your CCNA expire & sour!

I was teaching a SIP Essentials class for Alta3 Research and Global Knowledge the other day, and I had a student mention that he would be unable to attend class for a few hours after lunch, because he needed to go take one of the entry-level Juniper network exams. He went on to explain that he had been studying for his Cisco CCNP, but when he went to schedule the exam, Cisco informed him that he had allowed his CCNA to expire, therefore, if he wished to take his CCNP exam, he would have to take his CCNA exam […]

Review – SIP softclient CSipSimple

When I teach a SIP Essentials class, I always get asked about SIP clients. So many are available, so I’d like to begin asking the question, which ones are stand out? Which ones should we all flee from?

In this posting I’ll be reviewing CSipSimiple. CSipSimple was tested on my Nexus7 (Jellybean) on Oct. 31, 2012. The app is not available in the iTunes marketplace.

In a few sentences; CSipSimple is a free app, with a clean layout, no ads, many configuration options, as well as a handful of useful call features. I found it rather straightforward to configure a user account […]

Teaching SIP Essentials (onsite & online)

I am an instructor for SIP Essentials, a five day course offered by Alta3 Research that explores Session Initiation Protocol (RFC 3261), as well as it’s accompanying protocols. Material covered is outlined on their website, but covers SIP, SIP dial-plan routing, SIP routing via the DNS, configuring SIP systems, presence, how to read SIP requests & SIP responses, SDP, RTP, and so much more… (no really, I’m not just being cliché, read the extensive course outline here).

As a teacher, I must say, teaching SIP Essentials is a blast. The course includes over 30 labs, so there’s plenty of hands on activities in between my lecturing. The […]

A basic Asterisk v1.8 sip.conf configuration

One of the many goals I set for the students attending my Session Initiation Protocol class, is to leave them with an ability to maintain their own home Asterisk SIP PBX. After all, if you don’t exercise a muscle, it will atrophy; your SIP muscle is no different. It is only by rolling up your shirt sleeves, and diving into the fray, that you can really begin fully understand SIP (and those protocols it is accompanied by… SDP, RTP, DNS, etc).

So, my hope is that this post can take some of the mystery and apprehension out of the initial […]

Get started with Asterisk on Ubuntu 10.04 LTS (first time)

I’m a SIP instructor. I teach SIP Trunking courses on-site (I come to your location), and also offer on-line courses. I wrote this Asterisk ‘crash course’ while sitting in my hotel room one evening, in an attempt to help my SIP students continue their education outside of the classroom. If you find this posting helpful, or are impressed by what you see, and would like to hire a SIP instructor, contact me or Alta3 Research.
FYI – I wrote this document off the top of my head. I may have omitted a step or two, or gotten a command wrong. […]