by February 6, 2003 0 comments



Alfred Alvarez is a do-it-yourself entrepreneur who built up his fortune in trading. He traded in anything and everything, and kept close control of every activity. That was how he had grown rich enough to indulge in his one dream–to build a college in his home-town. A college that would be at par to the ones in
the better cities, the ones in which he could not study himself.

Work started a year back and the buildings were coming along well. He himself did not use computers much and became hooked to the Internet and e-mail only recently. He was determined to provide a PC with Internet connection to every student and faculty member, If it did not cost too much. He was currently engrossed in plans for the 100-seater computer lab.

Altogether, he planned to start off with about 150 PCs.

What was confusing him was the choice of Internet connectivity. He had about a dozen quotes in front of him.

Recommendations ranged from 64 Kbps ISDN all the way to 1 Gbps leased line to Mumbai, which was almost 150 km away. Prices ranged from slightly under a lakh all the way up to Rs 25 lakh and beyond. He did not understand most of the equipment quoted–firewall, proxy server, cache appliance. Nor was he sure what the hidden costs were. 

Although it went against his very nature, he would have to identify a trustworthy consultant and help him make sense of the whole thing.

Answer 1

P K Gupta
is Director, Strategic Development, Intercontinental Oper ations at Legato Systems

What is really needed is a reasonably reliable link (outages of more than half an hour are not acceptable), which would serve the users through a caching device. A caching device is a must as the users in a college typically look/search for the same information on the Net, and if that 

information has already been accessed then it should come from the caching device, rather than the site itself. This would give better performance to the users as well and save bandwidth
requirement. 

A proxy server, of course, is needed to share the Internet connection. The proxy can also be used to divide bandwidth between subnets to teachers and students (if they want to segregate the networks).

Also a firewall is something, which we will suggest to Alfred, this will allow him to host his college’s site on the IIS servers in the lab itself. May be, he could differ the firewall decision for some time and buy a lease line with about 128 kbps (with 128 kbps to the proxy server) connectivity with caching device. 

Now, we take a deeper look into details, doing some number crunching, as to how many concurrent users would be there, not more than 75% (75 out of 100) of the seats in peak loads as well. Now that translates into about 1.7 kbps (128/75) to each user, which I think is more than enough in a college environment. 

The use of a caching engine is the key to reducing costs significantly. It will also result in better performance to the users.

Answer 2

Yugraj Bhasin
is Deputy Engineer with CEDTI-
Mohali, presently working on the Telemedicine Project and is also 
responsible for CEDTI-Mohali 
network

Analyze requirements
More than pure bandwidth, you also need some other services. You will need a firewall, Domain Name Service, mail service, proxy server and internal Web server hosting the latest patches, updates and utilities to reduce repeated and redundant downloads of commonly downloaded files. The idea of hosting these services in house is to reduce the total bandwidth requirement and increase productivity, thus getting best value for money.

Bandwidth requirement
For the scenario given, it is recommended to have a leased line circuit as dial-up on ISDN is not a very practical solution. The cost of a dedicated ISDN port is marginally less than an equivalent leased line port. But, add call charges of a minimum of eight hours daily, and ISDN works out costlier than leased line circuits.

ISPs usually share a link with various other customers. For example, a 1:4 ratio for 64 kbps bandwidth means that a 64 kbps link is shared with four other customers. This comes out to 64/4 = 16 kbps theoretical speed. 

Dedicated links are also available but the cost of a dedicated link is very high. 

If we commit a minimum of 1—2 kbps speed per user, then for 150 clients we require a minimum of 150-300 kbps. Multiply 300×4=1.2Mbps for a shared link theoretically. But then, we live in a non-linear world, at least when it comes to capacity planning. 

Not all users are always online. In a typical college campus scenario, various other activities like classes and ‘labs’ or ‘practicals’ go on simultaneously. So the number of concurrent users on to the Internet will be much lower. Similarly the 50 other computers with faculty are also not always on the Internet. Further restriction on various bandwidth hogging downloads like MP3s and MPGs can be implemented. 

For practical purposes 64 kbps bandwidth is sufficient for 16-24 simultaneously browsing users (no downloads). Thus to begin with, 256 kbps would suffice for the purpose at hand. 

Check out the ISP 
The ISP provides the connectivity from your campus to their premises at the rated speed. After that, the quality of services is not guaranteed. So, while comparing various ISPs check out how their service is and what back-ends they have. Also check out things like network link media, external network links, services provided, back-up plan, distance of ISP from the campus etc.

A few ISPs lease the equipment you need for connectivity. In other cases, you have to procure the equipment yourself.

Maintenance of this equipment is usually in addition to the port charges. Watch out for other hidden expenses too. 

It’s always a good idea to start off with limited bandwidth and then gradually expand the requirement as you gain more
experience.

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