adventures of a VoIP / SIP / IMS trainer & contractor|


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 […]

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. […]

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    Acer Aspire One – OCZ Vertex II SATA II SSD – Ubuntu 12.04 – Grub Error – Cannot read disk

Acer Aspire One – OCZ Vertex II SATA II SSD – Ubuntu 12.04 – Grub Error – Cannot read disk

I recently purchased an Asus Aspire One NAV50 (532h-2789), I wanted to use it for writing, but found it a bit too small for that task. It sat around for a few weeks while I figured out what to do with it… and figure out I did. Turn it into a gaming emulation machine running Ubuntu 12.04, DosBOX, and ScummVM.

To peak the netbook’s performance, I upgraded the RAM to the (max) 2 gigs, and also upgraded the manufacturer’s 160 gig HD to a OCZ Vertex II SSD (SATA II & 120 GB). A video outline the details concerning this […]

Wasting the producers in Wasteland 2

I still remember pulling Wasteland for the Commodore 64 out of a bin of ‘throw-away’ software when I was 6. It was 1990, the NES was gaining popularity and quickly reshaping how people gamed. So, despite being 1989’s Game of the Year, Wasteland for the Commodore 64 was seen (prematurely) as ‘outdated’.

The box was similar in size and shape to that of a 33-LP vinyl, adorned in finely detailed hand-painted graphics; an artist’s vision of a post-apocalyptic southern California.

What inquisitive mind couldn’t be drawn in by that cover? A gang of five desert warriors facing a lone stranger midst the blown-out rubble of a city street. […]

Avaya phone-script from g350 to Ubuntu 12.04 TFTP server

As the Alta3 Research office network grows, I decided it was prudent to explore/develop how to bring up a TFTP (Trival File Transfer Protocol) server, primarily for use with our Avaya 46xx stations. In this post, I’ll explain how I moved the TFTP service from an Avaya G350, to an Ubuntu 12.04 LTS server.

Before I get started, some basic things about TFTP. TFTP is typically used for diskless boots (routers and phones), and across UDP port 69. TFTP offers no way to ‘list’ files available from the server. The protocol also lacks any security authentication, therefore, TFTP should never be implemented, […]