May 1999

Multimedia QoS Hits The Switch

BY MICHEL LAURENCE

The essence of a multimedia switch is an ability to fully support all the services that may be required in a multimedia environment, including transport and switching of voice, data, and video. In so doing, multimedia switches can enable service operating companies to consolidate their voice and data networks and thereby slash administrative and maintenance overhead. At the same time, a distributed multimedia switch allows faster implementation of the new services and applications required in competitive marketplaces. The key to achieving both of these benefits? A core switching technology that guarantees the quality of all transmissions through the multimedia switch, preserving the quality required for voice calls as video and data services are added.

In a conventional TDM-based voice network, quality is not an issue. Bandwidth is guaranteed, and transmission delay and delay variation simply do not occur. On the other hand, in conventional data networks, delay has been acceptable because data transmissions have not been as time-sensitive as voice. Until recently, guaranteed bandwidth has not been a concern in data networks. If data reached its destination sooner, so much the better. But if it got there a few minutes later, there was little impact.

ATM AND QoS
As the criticality of data has increased, however, so too has the need for guaranteeing both bandwidth availability and timely delivery. As a result, ATM data switches are becoming increasingly popular because they support Quality of Service (QoS). QoS provides the ability to specify acceptable delays and delay variations for each and every transmission, and to guarantee bandwidth as needed. The bottom line: ATM supports the switching reliability in the data world that has long been the standard in TDM-based voice networks.

In other words, while voice can certainly be carried over the T1 lines used for TDM voice networks with technologies such as frame relay or IP, only ATM can provide the guaranteed high quality delivery required for effective, consistent, reliable multimedia switching. Specifically, guaranteed QoS via ATM switching can restrict delay in a round-trip conversation to less that 25 milliseconds, the absolute maximum beyond which a discernible echo will be heard. Similarly, only ATM allows delay variations to be controlled. And, of course, only QoS can guarantee the bandwidth needed for multimedia communications.

LARGE DISTRIBUTED SWITCHES
QoS is particularly critical when constructing a large distributed multimedia switch because the various sites must all be linked on a single network where delays and bandwidth issues could otherwise arise. By comparison, with a single monolithic switch, over-engineering the network could minimize both problems. But as service providers increasingly look to incrementally expand their service areas, the distributed switch will become a far more cost-effective business solution that the more conventional large, single-site switch.

Recognizing the benefits of ATM and QoS, several large switch vendors are now considering ways of enhancing their existing products by adding an ATM switching capability so that they can be made multimedia capable. Most of these attempts, however, are limited by an existing, proprietary switching technology. As a result, whatever ATM/multimedia capabilities are developed, the switches will remain proprietary - despite the fact that they leverage a standards-based technology. To the service providers who end up using these switches, this means that the benefits of a standards based technology will be lost, and the expense and delays associated with a reliance on a single vendor for new applications and switch enhancements will remain.

Fortunately, the fact that ATM and QoS are standards-based is enabling development of an entirely new type of multimedia switch-one that is completely based on non-proprietary technology. These new multimedia switching platforms are already beginning to appear in the marketplace and are catching on because of the vendor independence they provide: where it could take as long as five years for a proprietary switch vendor to come out with a new feature, the same feature can be developed on an open platform in under six months.

The even better news for potential buyers of multimedia switches is that the cost of entry into this new manufacturing business is so much lower than it would be to create a proprietary switch de novo, that competition should be lively. At the root of this burgeoning industry is a unique network interface card (NIC) that can translate any multimedia service type -VOIP, voice over frame, video, data over Ethernet, etc. - to ATM, and of course, back again. Since this NIC is also standards based, the only other essential element for a large distributed multimedia switch is a conventional ATM switch.

OPEN PLATFORM QoS
One key benefit of this architecture as compared to a proprietary switch is that because the signaling software on the NIC is completely standards based, any switch developed with this technology can be seamlessly integrated with any other, similarly open, platform. As a result, service providers can achieve true vendor independence as they expand their distributed multimedia switch sites, yet they can still preserve the absolutely critical capabilities of ATM and QoS.

At the same time, these openly architected switches can provide all of the functionality of the more conventional proprietary switching environments, despite the fact that they are configured with off-the-shelf components. What it comes down to is this: thanks to QoS, an entirely new open platform distributed multimedia switch industry is being launched. This industry will benefit the end user with products that support any-to-any connectivity between all media types in a reliable, cost-effective, and standards-based way. For incremental expansion, availability of timely enhancements, and vendor flexibility, this new technology just can't be beat.

Michel Laurence is president and chief technical officer of InnoMedia Logic, Inc., Saint-Hubert, Quebec, Canada. InnoMediaLogic is pioneering an innovative family of telecommunication products based on their award winning ATM/TDM Bridging Technology. For more information, please visit their Web site at www.iml-cti.com.