Monday, November 7, 2011

An Asterisk Deployment [Small-Office]

Last post was a very advanced topic, so before posting the part-II of that post I thought to post something with less complexity.

We've already covered Installing Linux, Asterisk, Setting up very basic IVR and making calls within one server's domain.

In this post we'll discuss a small to medium environment deployment of VoIP server. [See attached Image]. This sort of deployments - with a variation of ±( 10-20) end points - is not very common nor successful as we'll see the pros and cons.

Deployment Scenario


Feature such as customized IVR, Call recordings, CDR reports ,and restricted dialing are most demanded in addition to the core use of Internal PBX.


The advantages of deploying VoIP with above features are mainly :

-Relative afford-ability :
Equivalent Proprietary equipment with these features are far far far more expensive with typically Panasonic and Nortel topping the list. China Analogue PBXs are easily available too but they don't offer all the features and flexibility.

-Cost effectiveness:
Even if China made PBXs or Panasonic Hybrid equipment may be used in place but the expansion factor in these environments cost way much more than options available in VoIP. Consider buying a 16 or 24 port card only to accommodate two new users whereas in VoIP all you need is buy two IP phones at max or minimum install a free Softphone.

Isn't it nice to change IVR prompts or options according to products or even change voicemail greetings without engaging any technical guys or vendors of PBX! though they still call me but every time I do it on phone or by remote desktop sessions in minutes. Now the only cost is of a cell phone call at max. Complex IVR designing and techniques are not commonly required in such deployments but there are cases when client's total emphasis is on a great IVR and then anything else. Anyways customizability is definitely a major attraction.
These are all the advantages of using OpenSource VoIP: The Big question is , are there any disadvantages of using VoIP in this scheme? My answer is YES, But these are all because of environment and people using it. So what are these?


-Multiple Single Point of Failures:

Since this type of deployments are majory based on cost effective factor with maximum cost cutting possible so they forget the factor of SPOF. As we can see that mostly they are using single unmanaged LAN switch which is often in everyone's reach and the network often experiences downtime, which brings down VoIP as well. Poor equipment handling is mostly the cause. I remember BAO JEE "If it can fail, it WILL fail" no matter how !! Single cable to Server, DSL modem and ATA (Analogue Telephony Adapter) with single power cable each, one Server, one FXO (Foreign eXchange Office) card are all Big Players in this area.

-Complex Management:
Since these environments are not mostly well educated and IT guys so you'll mostly hear 'em complain that it is complex to manage, and they can't or don't want to afford an IT specialist to handle this all.

-Call quality issues:
This is the most crucial part of, not just this but all, VoIP. Call quality in VoIP is major depending upon the underlying network equipment. Users want to download latest HD movies along with a perfect quality Call on the same network within the same bandwidth pipe. Also since the client is inclined towards poor call quality on VoIP so any issues with far end cell phone/network belong to 100% VoIP services now !! if PSTN lines are down - its all VoIP !!.

Those were some major disadvantages, some other like external dependencies, security, and maintenance cost are also in the list.

In continuation of this post I'll try come up with medium-large scale deployments as per my experience.


  1. Hi, i like your blog very much. What do you use to draw your diagrams. Kindly enlighten me i'm very interesred?

    1. I use Microsoft Visio 2013 or newer once with a Microsoft professional template and a background of my choice.