Frame relay blends QoS with speed
Praveen Goli, Product Marketing Manager, Ascend Communications Inc., Alameda, Calif.
Frame relay, the veteran high-bandwidth technology of network infrastructures, is keeping pace with the demands of the new public network by adding high-speed capability, capacity enhancements and quality guarantees. And, as service providers build networks optimized for data traffic, these new capabilities will help offer services to a dynamic and growing customer base.
The speed and capacity improvements come largely as a result of the emerging Frame Relay over Sonet (Frosonet) and Multi-Link Frame Relay (MLFR) standards. Frosonet provides specifications for frame relay to run at OC3/STM-1 or OC12/STM-4 speeds, while MLFR provides an incremental capacity jump for customers that are outgrowing T1 but are not ready for the speed or expense of DS3/E3 lines. The frame relay quality-of-service (QoS) capability will help service providers meet increasing demands for such things as Service Level Agreements (SLAs) and Customer Network Management (CNM).
Expected to be approved by the end of the year, the Frosonet standard maintains traditional frame relay advantages, such as the ability to engineer the use of bandwidth in the backbone and to lower overhead costs, while adding a number of benefits for service providers. For example, the standard includes the same High-level Data Link Control (HDLC) over Sonet mapping that is being used for Point-to-Point Protocol (PPP) over Sonet (PoS). This saves costs by allowing the same hardware to be used for both PPP and frame relay interfaces. The standard brings Sonet protection-switching capabilities to frame relay.
Basically, the MLFR adds scalability to frame relay networks, thus helping service providers keep pace with growing traffic demands and to extend services to customers. Typically, adding capacity beyond T1 and E1 lines involved provisioning a DS3/E3 line or using external inverse multiplexing equipment (IMUX) and was very costly. MLFR, by taking a software-based approach to providing higher-capacity frame relay access, is significantly more cost-effective and easier to deploy.
MLFR trunks are now available that combine multiple physical links between switches within the public network into a single higher-capacity logical facility. In the near future, MLFR will be available for User-to-Network Interface (UNI) connections as well. The aggregated links created through MLFR can be thought of as a single logical link to bridge the gap between T1/E1 and DS3/E3. For example, if a specific connection requires a 6-Mbit/second link, then a DS3/E3 line at 45 Mbits/s clearly results in wasted bandwidth, while a 1.5-Mbit/s T1/E1 line is not enough. With the MLFR, four T1/E1 lines can be logically linked to offer what appears to be a single 6-Mbit/s connection. This increases network capacity and maximizes bandwidth without unnecessary operations costs.
By bridging the gap between T1/E1 and DS3/E3, the MLFR standard allows network service providers to extend their service geography into areas that otherwise would not be justifiable. For example, a service provider might wish to offer frame relay services in new locations, but decides not to because it lacks DS3/E3 trunks in that location. With the MLFR, the provider can offer the new location NxT1/E1 service without incurring the cost of a DS3/E3 trunk.
Where the Frosonet and MLFR enable frame relay technology to meet the speed and capacity demands of the new public network, QoS capability enables frame relay to move beyond basic services. For example, revenue-generating services such as SLAs allow customers to select only the services they need.
And service providers now can also use frame relay as a platform for offering a broader range of applications. Some of these include Systems Network Architecture (SNA), voice over frame relay and premium Internet access.
In the case of SNA, there are more than 1 million ports still using leased lines. QoS capability with SLAs removes the last barrier that has kept many SNA users from moving to public frame relay networks and opens up a huge potential market.
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