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Issue of January 2003 
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Techscope 2003: WAN Connectivity
More options for WAN media

Network managers will now have many options for fulfilling WAN link requirements. It will become a challenging task just deciding which one to use. by C.N. Ram

India has come a long way since it opened up its Telecom sector. Over the past few years, we have made considerable progress in creating state-of-the-art, carrier-class telecom infrastructure in the country. This has been largely due to private operators investing heavily in infrastructure, and BSNL also catching up and upgrading its own infrastructure. Private service providers are continuously increasing their coverage and introducing value-added services. This has opened up new vistas for network designers.

The network medium, which physically carries data packets from one point to another, happens to be the most critical component in WANs. Reliability of the network hinges around reliability of the medium, as it is the weakest link in the overall network architecture.

In the years ahead, leased lines need not be the only choice for the network medium.

New Challenges
This has posed some new challenges and opportunities to network managers. In the old days, when the requirement for a WAN link arose, the network manager did not need to think about the options as there was only BSNL (for leased lines). He had to apply to BSNL, wait for them to commission the link as per their time frames and then pray that the line was up and running. Users did not expect too much and were contended with whatever uptime was available.

VSATs have been around for quite sometime now but are typically unaffordable due to high costs. The cost factor arose because of the unique frequency band that was used only in India. VSAT equipment had to be manufactured explicitly for the Indian frequency band, so economies of scale could not be achieved, leading to higher equipment cost. To add to that, only ISRO satellites were permitted, and licence fees were very high.

In 2003, the scenario will change drastically. Network managers will now have many options to choose for fulfilling WAN link requirements. I'm sure it will become a challenging task to decide which one to choose.

Year 2003
The reasons attributed to this new challenge are many. On one hand, BSNL/MTNL have achieved substantial performance improvements. On the other, more private operators are spreading their coverage and introducing value-added services.

VSAT technology has also advanced and broadband VSATs have arrived. Due to availability of the KU band in India, cheaper VSAT equipment is available, which makes the VSAT costs almost equivalent to that of other media.

Mobile operators have introduced data services based on GPRS and CDMA. To top it all, radio technology has also advanced—cheaper and higher bandwidth radios are available at much lower costs. More frequency bands are permitted making it more feasible and reliable.

All this leads us to the conclusion that the Indian market has matured in terms of WAN media availability and reliability. This is the reason why network managers will have to take more informed decisions while selecting the medium.

While there can't be a thumb rule which states that a particular medium is better than another, general guidelines will definitely be helpful to arrive at the best bet in a given situation. The following general considerations will gain significance in the decision making process.

Leased lines
So far leased lines were only available from BSNL/MTNL, and performance was very inconsistent. Single window co-ordination has been a major issue in the commissioning and upkeep of the lines. But there is considerable improvement in consistent performance and accountability. This is largely due to competition created by private operators.

A leased line is an ideal medium for bandwidth hungry and low latency applications. (e.g. multimedia applications).The performance is much better in metros than in urban/rural areas. The commissioning time is a little higher than for all other media and there could be issues in redeployment in case your location is liable to shift. Normally you are bound to the service provider for a year by paying advance rental.

Leased lines are now offered by many operators. If you have a presence all over India, choose an operator who will have presence in multiple locations.

Usually, both capital and revenue costs are medium. Since tariffs depend on distance, long distance leased lines may attract high revenue costs. However, due to increasing competition, leased line costs are expecetd to slide further.

VSATs are suitable for applications characterised by bursts of traffic, or applications which work on a broadcast basis. However, due to the inherent latency of the VSAT technology, it may not be suitable for real time applications.

With the introduction of KU band-based VSATs, it may be an ideal medium for applications like Internet browsing where traffic is asymmetric and latencies are tolerable.

VSATs are generally hassle free from a commissioning and maintenance viewpoint. However, clear rooftop space of about 10 square feet is required for the installation. Relocation is also not an issue subject to availability of rooftop space. One should be aware of extra-terrestrial phenomena like sun outage, which render VSATs unusable for that duration. Such phenomena are not within the service provider's control. But generally, uptime is quite good.

There has been a dramatic reduction in the equipment cost and operating cost of a VSAT over the past year. While equipment cost is more or less similar to leased lines, operating cost may depend on the volume of traffic pumped in to the VSAT. For very high traffic, costs could turn out to be much higher than leased lines.

Line-of-sight Radio links
Radio technology has shown significant improvements in terms of availability of higher bandwidths over the past few years. Equipment is now available for as high as multiples of E1 link capacity, at a reasonable price point.

Reliability has also improved as multiple frequency bands are released to commercial operators.

Goverment has de-licensed the 2.4 GHz frequency band to encourage widespread use of Wi-Fi (802.11b/a). However this is bound to raise network security issues, which are being addressed as new standards for WLAN emerge.

Radio links work well in urban and rural areas where it is difficult to lay cables—the only restriction being feasibility of line-of-sight. Another potential deployment of radio links could be to connect clusters of offices within a city to a central office.

There is no bar on the type of applications, which could be real time multimedia applications or other bandwidth-hungry applications. One limitation is on the distance that can be covered by a single link. Another constraint is that, at times, it becomes impossible for the provider to trace and curb the cause of disturbance on the link, especially if it happens intermittently.

Radio links usually entail the highest equipment cost while the operating costs are comparable to that of leased lines.

Data over cellular
Data over cellular is a relatively new offering in the market. It is expected to mature and become more and more dominant in the marketplace in the years ahead. In its present form it is suitable for low bandwidth applications such as ATMs or Point-of-Sales terminals. However, as the bandwidth offering improves, it can be a real threat to all other media.
One has to watch for this medium in the coming years. Equipment costs are very low and operating costs could also be comparable to that of leased lines.

Managed network services
These are value-added services (such as VPN) offered by service providers. The choice of media depends on availability in a particular area. This type of service is generally suitable for small and medium enterprises who may not want to be concerned with the maintenance of their wide area networks. The service provider manages and monitors the entire WAN infrastructure, including the CPE (customer premise equipment). Managed services are a good bet for applications that have moderate traffic.

VPN will become an attractive proposition in future as security and QoS issues are addressed with advancements at the higher layers of network topology. The quality and quantity of Internet bandwidth availability is also expected to improve significantly, which can help VPN be more suitable even for critical business applications.

In summary, easy availability of high speed and reliable connectivity in the country can lead to more applications being launched on corporate networks (e.g. video conferencing, intranet applications, group collaboration etc). I believe year 2003 will mark the beginning of a very challenging and rewarding era for network managers who were so far constrained by the laws of the land.

The writer is Head, Information Technology, HDFC Bank

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