Bringing QoS and "any to any" connectivity to frame relay
 
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Since frame relay has long been used primarily for transporting bursty LAN traffic, which is not particularly delay-sensitive, quality of service (QoS) in frame relay networks has not been much of an issue. In general, the limited QoS that the committed information rate (CIR) offers has been sufficient. As frame relay traffic expands to include voice and other traffic types that may warrant a higher priority over other traffic flows during periods of network congestion, some customers may become interested in adding QoS options to their frame relay services.
Multiprotocol Label Switching (MPLS), an emerging IETF standard, is one way to do it. Among other things, MPLS labels provide the ability to differentiate service classes for individual data flows. Most often MPLS software joins ATM switches to create an MPLS network that maps IP precedence priorities to ATM's classes of service.
This is basically what is happening in AT&T's IP-Enabled Frame Relay Service, which represents the U.S.'s first MPLS-based IP virtual private network (VPN) service and is delivered off of Cisco Systems' MGX ATM/MPLS edge switches. Users who are already comfortable with their frame relay equipment and interfaces simply purchase a frame relay access link to AT&T's network. The MGX converts frames into MPLS-enabled ATM cells for distribution across AT&T's MPLS/ATM-based IP VPN.
In this way, users can actually specify ATM classes of service (constant bit rate, variable bit rate, etc.) for a particular traffic flow but stick with their familiar frame relay interface. Instead of buying frame relay switched virtual circuit services (not available from AT&T, but available from MCI WorldCom), users can get the ubiquitous connectivity by instead purchasing a committed data rate through the IP VPN cloud.
Steven Taylor, consultant and broadband packet evangelist, and Joanie Wexler, an independent networking technology editor and writer, team up to bring you this analysis and commentary. Taylor specializes in education and market analysis, and Wexler adds incisive reporting and research. For more detailed information on most of the topics discussed in this newsletter, connect to www.webtorials.com, the first Web site dedicated exclusively to market studies and technology tutorials in the Broadband Packet areas of Frame Relay, ATM, and IP. Feedback and additional topic ideas are welcome. Please contact taylor@webtorials.com or joanie_wexler@mindspring.com.
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Archive of Network World on Frame Relay newsletters
