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Inbox (March 2002)

VoIP eye-opener

Dear Sandeep,
The cover story in the February 2002 issue on VoIP technology was very informative. I am sure that it will be an eye-opener for many Indian companies and they will subscribe to this technology in its networks. I have a few queries.

1) If the technology is really so good why didn't the Indian Government make it legal for telecom companies and organizations to use this technology earlier?

2) How will voice packets move along with IP data packets?

3) Will VoIP be allowed only on VSNL's network? Will other players like Bharti Telecom and Reliance carry VoIP traffic as well?

Mukul Garg
Dear Mukul,

Here are the replies to your queries.
1. The Indian Government was trying its best to protect its interests in the state-run VSNL and BSNL; the international and national long distance telecom players respectively. Opening VoIP to enterprises and individuals would have affected the revenues of these players. However, even now VoIP is allowed in a closed loop, say over a Frame Relay.

2. With the use of VoIP technology, voice will convert to IP data packets. These packets will move over a data network in the same way any other data packet would move. The VoIP packets will be routed and switched normally and will be reconstructed as voice signals at the receiving end.

3. VoIP will be allowed over any private or public network. Any telecom company or ISP can offer VoIP services to its customers.

The Government still needs to clarify many issues pertaining to VoIP, you will get a clearer picture only after April 1st, when VoIP will be legalized.

VoIP budget

Dear Sandeep,
The cover story on VoIP in the February 2002 issue is very informative. I work in the capacity of Manager, Business Development with an ISP in Gujarat. How can I calculate the cost of deploying VOIP in my network? How much will I need to invest in hardware, software, and other infrastructure? How will I calculate the ROI?

Shrenik Gandhi

Dear Shrenik,
It is difficult to put a figure on the cost of deploying a VoIP solution. Calculating the ROI on VoIP merits a whole article in itself, something that we will feature in one of our next issues.

Also, calculating ROI varies from enterprise to enterprise. In case of an ISP, the parameters for calculating ROI will differ significantly.

A good idea is to seek advice from VoIP vendors like Cisco, 3Com, D-Link, etc. They will be very eager to help and you can pick and choose a solution that suits you best. We are forwarding this mail to the respective companies.

Restricted access

Dear Soutiman,
I am a scientist at DRDO, We have a 130 node LAN in Dehradun. Our Intranet connects to Delhi and Bangalore through an ISDN link. The Dehradun LAN also comprises of a main server, Web server, a switch and a router.

I want to restrict particular LAN users in Dehradun from accessing the Web server in Delhi. I know the IP address of the Web server in Delhi. Do you think I might need a firewall?

Ezhil Thiruman

Dear Ezhil Thiruman,
You don't need a firewall because a firewall is meant for keeping outsiders away from your internal network and not so much to keep internal users away from another network.

Restricting users in Dehradun from accessing the Web server in Delhi will require a little effort on the part of the systems administrator in Delhi. He simply has to block IP addresses of the LAN clients in Dehradun.

The functionality is present in the Web server OS which may be Unix, Solaris, or NT.

IP address issues

Dear Soutiman,
I am a regular reader of your magazine. I have a few queries. Do you need to register IP addresses for use in an organization? If so, where do we have to register? Do we need to register addresses of each terminal and router? And what is the main function of NAT?


Dear Asif,
You can assign IP addresses at random within an isolated network as long as each one is unique. However if you want to connect your private network to the Internet you have to use registered IP addresses to avoid duplicates. The InterNIC Registration Service assigns Internet addresses from the following three classes.

Class A - supports 16 million hosts on each of 127 networks
Class B - supports 65,000 hosts on each of 16,000 networks
Class C - supports 254 hosts on each of 2 million networks

You can visit the following links for more information about assigning IP addresses.

NAT (Network Address Translation) is an IETF standard that allows an organization to present itself to the Internet with one address. NAT converts the address of each LAN node into one IP address for the Internet and vice versa. It also serves as a firewall by keeping individual IP addresses hidden from the outside world.

Which device is it?

Dear Soutiman,
I liked your article on VoIP called 'VoIP: Packaged voice and more' in the February 2002 issue. I am interested in exploring VoIP options in my organization. In an architecture diagram on page 26 you have named a network device as 'PWR'. What is the device all about?

Krishna Mohan

Dear Krishna Mohan,
Thank you for appreciating the article. I am sorry that the diagram did not explain the meaning of the term 'PWR'. The device is supposed to be a switch. Cisco has a LAN switch of the same model name. The device should have been simply marked 'switch'.

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