IP switching to the rescue

As service providers face growing residential and commercial demands for Internet access, they are finding that the requirements for bandwidth and access ports exceed the supply.

The Internet's original messaging-based applications now compete for bandwidth with multimedia applications such as Web browsers and newly emerging applications such as Internet protocol TV, voice over IP and desktop videoconferencing.

Today's router-based Internet topology will be unable to cope with these requirements despite faster router deployment. That's because the main factors limiting router performance involve examining the destination addresses of incoming datagrams, indexing into a routing table to determine the next hop, and then copying the incoming datagrams to their outgoing interface. The routing look-up task is not simple, and it is unusual for networking routers to be able to perform more than 100,000 address look-ups per second.

Alternative techniques to complex routing look-ups are generally known as "label swapping" and are approached in different ways: The two techniques attracting the most attention are the evolving multiprotocol over asynchronous transfer mode standard and the more established IP flow management protocol standard (RFC 1953).

The IP standard addresses the growing volume of multihop software addressed traffic by providing a cut-through switching facility of a multiservice ATM switch to provide IP switching. The multiservice ATM switch can provide native ATM (non-IP traffic) switching, frame relay switching, circuit emulation and transparent bit-sync transport services for carriers and Internet service providers.

The perfect combination The ideal IP switching solution exploits the speed, capacity and multiservice traffic capabilities of ATM as a connection-orientated application and combines it with the simplicity, scalability and robust nature of the connectionless IP. Its advantage is that it requires the standard IP routing protocols, avoiding the need for a signaling protocol or any address resolution protocol.

Many experts believe that this combination provides the underlying support for emerging multimedia applications that will increase the demand for bandwidth and highlight the need for efficient, manageable IP switching applications. However, native ATM, frame relay and circuit emulation applications cannot be overlooked in the IP switching equation to provide a true multiservice, multiprotocol implementation on the same platform.

A look at IP switching capabilities with a multiservice ATM switch shows multimedia LAN-to-LAN, LAN-to-WAN and IP-over-frame relay applications (Figure 1). Three multiservice ATM switches are interconnected with two IP controllers and two IP gateways.

There are three major objectives of this solution. The first is performing measurable tests to verify the advantages of cut-through switching and the associated performance improvements over store-and-forward multihop routing.

Second is segregating traffic under different quality of service (QOS) profiles and detecting flow-orientated IP traffic and the activation of cut-through.

The final goal is observing a number of Multimedia applications to visually judge the QOS associated with IP switching and the superior traffic management within a multiservice ATM switch. These applications include Web browsers, videoconferencing and video-on-demand solutions. They also demonstrate interoperability and service interworking with IP switching technology and typical IP traffic associated with the Internet.

The multiservice ATM switch is loaded with traffic to the maximum possible levels in this environment, and each application is stress-tested under load. The average throughput increase in the cut-through configuration is about 70% above the average throughput gained in the store-and-forward configuration. Note that these figures were achieved when the network was severely under-used from a connection perspective and the routing tables within the controllers and gateways were minuscule compared with a typical router on the Internet.

In a typical router network, the average throughput increase would be significantly greater because of the large number of routing tables and the limited performance of their ability to copy data between interfaces. In addition, the results obtained in the traffic prioritization tests clearly showed that a multiservice ATM switching solution can easily handle congestion in the network when it came to the QOS agreement thresholds set for each connection.

The major advantages can be summarized as follows: * IP switching is optimized for very high IP throughput. It has been estimated that 90% of byte-measured traffic would be suitable for switching in ATM switch hardware.

* IP switching relies on standard IP routing as the controlling software in the network, enabling a network of multiservice ATM switches to scale as easily as any routed IP network. Each ATM switch node can scale well above the highest level router available today.

* By relying on standard IP routing software, the ATM switches simplify network management because all devices in the network are controlled by standard IP routing software.

Experts see this combination as the underlying support for emerging multimedia applications that will increase the demand for bandwidth and highlight the need for efficient, manageable IP switching applications.