For strategic purchase of WAN switches, there is a
trade-off among the following general criteria:

• Functions and features

• Scale and expandability

• Performance

• – Throughput

• – Congestion tolerance/control

• – Latency

• Network management/operational considerations

• Vendor support resources/architecture/other vendor considerations

• Ability to accommodate new technologies

• Price

There are two options before operators today—multiservice switches and Ethernet switches.

n Multiservice Switch: This is a good option for the incumbent operators, who already have TDM-based data services. Competition is making them also offer new data services such as DSL and IP-based services such as VPN. ATM’s scalable bandwidth and ability to serve as a common infrastructure for a multiplicity of packet, cell, and circuit-based network services has made it an attractive choice for service providers. Multiservice switch is both used at the core of the network as well as the edge for last mile access. The edge multiservice WAN switch usually has provisions for multiple access technologies such as ATM, Frame Relay, and Ethernet.

Modularity: E1 lines (2 Mbps) are the norm in India today, but this does not mean that users will not demand data links of higher capacity tomorrow. Already several companies, especially tier-2 and tier-3 service providers, are having multiple E1 lines in their main offices. Tomorrow, there will be demand for nx2Mb links, even STM1 and STM4 links. So the equipment that service providers purchase today should be modular with option of scaling up rapidly and scope for adding large number of links.

Technology Versatility: In a highly competitive scenario with multiple players, there will be need for operators to match the different kinds of services that competitors might offer in future. Also, one is not sure which access technologies will gain usage among users. Hence, it is better to go for equipment that will support the maximum number of access technologies.

Differential Services Capability: In a highly heterogeneous market as India, there are big multinational users who have the need for the best-of-quality service at any cost and there are also such users who would want to go in for the just-enough bandwidth and minimal service level guarantees. Operators must keep in mind that they have to satisfy both ends of the spectrum.

Operational Flexibility: The equipment must have a network management system that is highly user-friendly so that for the operator’s engineers there is minimal fuss in provisioning and maintaining the services. It is also highly recommended that the equipment has a mechanism where the intelligence of the network is taken to the edge of the network, with such operations as dynamic change of link capacities and choice of service levels being in the hands of the users.

Intelligent Fault Resolution Mechanism: The equipment must have the ability to monitor the network performance and pre-empt network faults. It is a huge value-add if the operator is able to know that a link is going to go down and the same is communicated to the customer. If a backup link is provided while the primary link is down, the value-add is even greater.

n Ethernet Switch: Ethernet has gained favor worldwide for its simplicity, performance and low cost. Today, Longreach Ethernet has become a serious option for service providers to provide last-mile high-bandwidth links for both data and voice services. This gradual acceptance of Ethernet among service providers have pushed several vendors to develop a slew of next-generation, high-performance 10 Gigabit Ethernet solutions.

Ethernet is especially being favored by greenfield operators who do not have to go for traditional TDM-based transport technologies for the bouquet of data services that they are planning to provide through their metro optical rings. Since these operators have laid their optical fiber touching various commercial hubs in the metropolises, what they are looking for is the best last-mile access technologies. It is here that Ethernet switches figure in their scheme of things, in addition to DSL and Co-ax.

Criteria for Selection: Line-rate, Non-blocking Performance: The current generation of switches and routers were not built to handle the increased speeds and scalability required to support this new high-performance technology. In fact, most switches today have limited bandwidth capacity per line card slot, preventing them from delivering full line-rate, non-blocking multi-gigabit Ethernet. Since some of the Ethernet links have be at aggregation points in the network, line-rate, non-blocking performance is an absolute necessity.

n Carrier-class Software: While the hardware are being developed to support high-speed transport, the software that switches or routes the traffic have to be also designed to suit WAN applications.

n SDH Interoperability: SDH networks will be there, despite the popularity of DWDM. They are an integral part of the WAN environment. Therefore, new solutions, including 10 gigabit Ethernet, must offer a cost-effective way to interoperate with existing infrastructures and support native packet over SDH and Ethernet over SDH interfaces.

n Scalability: New equipment must have scalable capacity to support at least three to five years’ worth of network growth. Next-generation solutions must have the backplane capacity, port density and overall system architecture to scale along with the network

n Carrier-class Availability: Regardless of the application, users share a common need for high reliability and availability in their networking equipment. Redundant switch fabrics, route processors, power and fans are a given in today’s environment; other techniques are also required to improve network availability.