Days of our Lives!

June 17, 2008

BVoIP – a short history

Filed under: Tech,work(place) — Santhosh @ 6:12 PM

Note: To be completed…

The basic setup of a VoIP system closely follows the traditional telephone network. Telephone numbers are replaced by IP addressed phone numbers, codecs are used to convert the analog voice signal into packets, and packet switching replaces the traditional circuit switching. Initially, it was possible to place just on-net calls – calls between two VoIP systems in the same network. This however would have given very limited commerical viability and development turned towards integrating VoIP with the mainstream PSTN network.

Even with the traditional telephone system, companies quickly realised that it didn’t make financial sense to go the PSTN every time to route calls even though both the caller and the callee belonged to the same network. The Private Branch eXchange or PBX was developed so that organisations having a large number of telephones could take care of internal and first-level switching and call routing, maintain extension numbers and manage the features provided for the telephone numbers under it.

Companies then realised that they were now spending too much resources on things that weren’t their core competency. For example, a Walmart or a Disneyland now had to employ people and dedicate time and money in maintaining all this equipment even though all these were just supplements to their actual businesses. This gave rise to the IP Centrex service (Centrex – CENTRal EXchange) where the PBX for the client is maintained by the telecom service provider.

There are two ways in which you can maintain and use VoIP –
1) a dedicated physical VoIP phone (like the ones we have in Manyata) connected via the LAN cable
2) VoIP software installed in a computer.
Either way, since the IP phones use the Internet, they can be administered by the provider anywhere there’s an Internet connection so that a VoIP phone is essentially like a mobile phone.

The Customer Premise Equipment (CPE) and the VoIP software are responsible for the various features and add-ons that you may want to opt for (apart from the mandatory functions like Dynamic IP Address resolution) : Caller ID, Call waiting, Call transfer, Auto Attendant, Three-way calling, Toll Free, voice mail, attaching voice messages to an email, etc. This part of the VoIP world is still in it’s nascent stage and a desi approach should make available third party software as add-ons and tweaks to ‘customize’ our VoIP phones to play a “busy” signal or a “non-in-service” message, or to even be able to ask our managers to join a conference bridge where 5 different voices keep telling how good we are.

One of the challenges faced by VoIP phones from totally replacing the traditional handsets is a power source – VoIP needs a constant power supply to be plugged into for it to work so that a power cut may effectively mean you’re without a phone. Also, since it’s internet based, VoIP is also susceptible to worms, viruses and hacking, although this is very rare and VoIP developers are working on VoIP encryption to counter this.

To be updated:
SIP, S77, authorized interception
problems in dialling Emergency 911 calls since VoIP uses IP-addressed phone numbers.
economics and infrastructure requirements
basic telecom – packet or circuit switching, codecs, etc

VoIP phone/computer <–> PBX <–> PSTN <–> PBX <–> VoIP phone/computer
| (if callee is within the loop)


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