Equipment vendors are producing mature, standards-compliant frame relay access devices (FRADs) for little more than the price of a high-end modem, while also enablin g service consolidation and boosting both performance and availability. Frame relay has proven itself a scalable, wide-area data service, and those willing to adopt new applications can save their corporations some big bucks.

The latest generation of FRADs can do it all: route IP, IPX, AppleTalk and SNA; consolidate voice and video; and intelligently organize and manipulate these data types to ensure quality delivery even in the presence of unfavorable congestion within public frame relay networks. Good FRADs also allow for centralized management and performance monitoring so that administrators can evaluate bandwidth requirements and verify that the carrier is meeting service-level agreements.

As frame relay carriers continue to upgrade their backbone equipment to meet rising customer demand for bandwidth and services, FRADs are growing in functionality to match carrier service levels. They now serve applications that utilize the extra bandwidth and reduce delay s. Some FRADs function as little more th an interfaces to the frame relay network, letting devices that are not frame relay-aware attach to the WAN as a serial device. Slightly more sophisticated units incorporate the bridging or routing of LAN protocols. Some FRADs are solely for voice transmission while others are tailored for video-streaming.

Regardless of the type of FRAD, it must handle error correction. Because frame relay depends on improved technology, it assumes error-free lines. Leaving the error-correction and flow-control functions to the end points (customer premise equipment) is one of the reasons frame relay can achieve the lower overhead required to move data packets at much higher rates than previous technologies, such as X.25.

What to Look For The most common FRADs are designed as narrowband devices--in other words, they're not equipped to handle the amount of traffic that would be found traveling between large corporate sites.

Full-fledged routers with frame relay support are better-suited for this task because they have the processing power and advanced software to handle intense loads. But for branch office connectivity, where up to 10 users, for example, need access to corporate resources, FRADs are a perfect fit. Note that the term FRAD can apply to a broad range of products that access the frame relay network.

· Port speed and CSU/DSU support Frame relay service is offered over a dedicated circuit, which accounts for a significant portion of the entire cost of the frame relay connection (40 percent to 60 percent). Currently, most carriers offer frame relay over 56-Kbps digital data service (DDS) and fractional T1 services. Most carriers report that roughly 60 percent of customers have 56-Kbps DDS connecting sites to the corporate network. This isn't surprising because of the relative prices of 1.5-Mbps T1, which sometimes are quintuple the price of the 56-Kbps DDS. Many FRADs support T1 speeds, though this is as far as you would ever want to push a low-end FRAD.

Th e CSU/DSU options are an importan t consideration. Many FRADs offer separate built-in CSU/DSUs for 56-Kbps DDS or T1. FRADs with built-in CSU/ DSUs help reduce costs and simplify installation by consolidating the unit and connection, possibly giving extra monitoring capability. However, this feature may lock you out of an easy upgrade path for more bandwidth.

To download an Adobe Acrobat .pdf format version of Frame Relay Access Devices Buyer's Guide charts, click here.