The enterprise connectivity scene in India has changed quite a bit in the last one year. Competition and the emergence of a variety of technologies have changed the rules of the game. Here is more on the new landscape.

Technology Options

Terrestrial Data
l IP VPNs: It is the hottest WAN technology today. IP VPN is "an emulation of a private wide-area network (WAN) using IP facilities, including the public Internet or private IP backbone". From this definition, it follows that an IP VPN could either be CPE-based or network-based. A VPN can be built on any of the layer-2 technologies, including frame relay (FR); however, that would just be a VPN rather than an IP-based VPN. The primary advantages offered by IP VPN are based on two parameters-first, IP VPN is a connectionless service in contrast to the layer-2 ATM and frame relay services, and second, IP VPN is a ubiquitous (any-to-any) service in contrast to point-to-point inherent feature of the ATM/FR service.

IP VPN services are recognized as the next evolutionary step for corporates that are currently using the more expensive FR or ATM VPN services, private line services or the public Internet for their connectivity needs. Also IP VPNs are expected to increasingly replace CPE-based VPNs as these services offer more security than the Internet, cost-effective any-to-any connectivity, and the capability to carry multiple types of traffic for customers who want an integrated network solution. According to a recently released report on IP VPNs by In-Stat/MDR, a major driver for uptake of IP VPN services was found to be the increasing momentum towards convergence of voice, data, and video traffic on a network-based IP VPN service. IP VPN also has the ability to offer more innovative offerings such as SSL remote access, Wi-Fi hotspot VPN access, and multicasting over VPN services. Event though such services are not available in India as of now, most services providers are expected to offer them soon.

Two unique complementary VPN architectures based on IP security (IPSec) and multiprotocol label switching (MPLS) technologies are emerging. IPSec-based VPNs are very popular among all service providers. On the other hand MPLS-based VPNs are used for more sophisticated and manageable networks capable of supporting transparent application support across diverse platforms. Using VPN network one can run applications like e-commerce, application hosting, and multimedia applications that will enable service providers to generate new incremental revenue and maintain long-term competitive advantage.

MPLS is a high-performance packet forwarding technology that integrates the performance and traffic management capabilities of data-link layer (Layer 2) switching with the scalability, flexibility, and performance of network-layer (Layer 3) routing. It enables to meet challenges brought about by explosive growth and provides the opportunity for differentiated services without necessitating the sacrifice of existing infrastructure.

Some of the features of MPLS are: data can be transferred over any combination of Layer 2 technologies; support is offered for all Layer 3 protocols; and scaling is possible well beyond anything offered in today's networks.

Legacy Technologies
l Asynchronous Transfer Mode (ATM): The world's most widely deployed backbone technology, ATM is a standards-based transport medium that is widely used within the core-at the access and in the edge of telecommunications systems-to send data, video and voice at ultra high speeds. It can be used to send data, video and voice at ultra high speeds. ATM connectivity offers high quality of service (QoS), and network efficiency.

It provides a common technology platform onto which multiple service types can converge with distinctive and quantitative QoS guarantees. Today, ATM scales form T-1 to OC-48 at speeds that average 2.5 GB in operation, 10 GB in limited use and spanning up to 40 GB in trials. However, ATM is now losing out to MPLS as the preferred enterprise WAN connectivity technology because of its superior cost and performance advantages.

l Frame Relay: This is a form of statistical multiplexing, a method of dynamically allocating transmission bandwidth to more efficiently share the high-cost links. In this way, a single local access line can support connections to many remote sites.

Traditionally, it has been used for bursty LAN and WAN traffic. With the development of frame relay quality of service, FR is also well suited for delay-sensitive traffic such as voice, video conferencing and interactive applications. But, as with ATM, FR too is now losing out to MPLS.

l IPLC: It's a TDM circuit switch used for point-to-point international connectivity. It offers a throughput of 64 Kbps and multiples. IPLC can be provided through submarine cables, satellite or through a mix of both.

Indian operators like VSNL, Data Access, and Bharti provide the Indian side of IPLC while the other half (in the country of destination) is taken care of by the tier 1 operators of that country. And since IPLCs connect two half circuits of two different carriers, providers often play the buck passing game whenever there is a problem.

Satellite Data
l VSATs: Written off many times because of growing ubiquity of terrestrial data networks and solutions and also because of their capex in deployment, VSATs services are still a good bet for enterprises looking at reliability and dedicated bandwidth. Also, VSATs are the most effective backup to terrestrial data services. VSATs are easy to install, can be deployed fast and serve even the most remote of locations. Moreover, in recent times with equipment and running costs going downwards, they have become more affordable to small and medium businesses.

While satellites have become more powerful on one hand, on the other, VSAT technology has become more standardized offering hitherto unavailable cost and performance advantages.

VSATs are today more superior indoor units with compact, ASIC design and work as full-fledged routers with 10/100 Mbps ports, routing support, serial and Ethernet ports, SNMP, DHCP, QoS and filtering. Moreover, there has been a movement towards more standardization in technologies with DVB-S emerging as the standard for downlink channel; and IPoS, DVB-RCS and DOCSIS for the return channel.

Also, use of Ku band as the de facto frequency band for VSATc communications offers new cost and performance advantage. Also with government allowing the use of smaller dishes (1.2 m for Ext-C Star and 1 m for Ku Star; 2.4 m for Ext-C Mesh), users would not need to spend nights on rooftops, as VSAT equipment can now be installed indoors. Overall, VSATs have become smarter and more powerful networking and telecom devices.

Access Technologies
l DSL: Good for small businesses, DSL utilizes standard telephone lines to move data at higher speeds. The service works best for users who live within three-and-a-half miles from the telephone company's central office or where the DSL equipment is located-the more the subscriber is closer to the central office, the better the speed that he gets. And even if subscribers were further than the prescribed distance from the central office, they would get a far better speed than through a dial-up or a cable modem. This is because DSL is rate adaptive, that is, it adapts the communication speed to the user's modem and distance from the service provider's point-of-presence. In fact, Rate Adaptive DSL is being touted as the best bet for residential broadband as it provides maximum bi-directional bandwidth from a DSL circuit. Subscribers get a single secure line that directly connects to the service provider and users get dedicated bandwidth, as the line is not shared with any other user. All DSL technologies exploit the available spectrum in copper telephone lines, employing advanced modulation techniques to carry high-speed data transmissions. The basic differences among the DSL technologies (IDSL, SDSL, HDSL, ADSL, and VDSL) lie in their communication speed, operating distance, and suitable applications. Apart from using the existing copper lines, all DSL technologies offer certain other benefits like partitioning voice and data traffic.

l Leased Lines: Leased line provides corporates a clear channel bandwidth of 64 kbps and its multiples. These circuits can be used for point-to-point leased line, inter-office connectivity, wide area connectivity, and local loop access to ISPs. E1 link is ideal for large corporates, which require a large number of telephone lines. This is a 2 Mbps link that can carry voice or data channels.

l ISDN: Corporates opting for ISDN get two channels that can be used for voice or data. They can use these channels for high-speed Internet access and video-conferencing. ISDN is available in two variants- basic rate interface (BRI) and primary rate interface (PRI). Basic rate ISDN divides the telephone line into three digital channels-two B channels and one D channel. The two B channels are used for voice, data or video at rates of 64 kbps. The D channel is used for control and signaling. The main advantage of ISDN is that one can access the Internet on one channel and make or receive voice calls on the other. PRI divides the telephone lines into 30 B channels and one D channel, which can be used simultaneously.

Voice
l Managed Voice over IP: If an enterprise spends too much on intra-office long distance calls, it can go for managed voice over IP services. With IP as the underlying technology, VoIP offers great cost advantages even in these times of decreasing long distance costs.

Apart from costs, VoIP also offers benefits in terms of features and scalability. In managed VoIP, while the customer premises equipment is owned by the user enterprise, the IP link is managed by the operator who guarantees quality of service and network uptime.

l Centrex: Centrex or central office exchange service is a flexible communication tool designed for all types of corporates. It offers the benefits of an EPABX without the corporate investing in it. Since the main switch provides this facility, there is no need for the user to worry about its maintenance, upgradation or obsolescence.

Corporates opting for centrex can also use it through interactive voice response (IVR). It supports value-added services like call transfer; call pick-up, auto call back, and direct inward dialing (DID). Centrex includes DID facility on each line and can be optionally integrated with the existing EPABX systems. BSNL is offering centrex service in India.