October 1999

Extend The Life Of Your Frame Relay Network

BY JOE LUECKENHOFF

Managers of Frame Relay (FR) networks are a little apprehensive these days, and for good reason. They've invested heavily in what is now considered a mature technology and they've come to depend on the reliability and performance levels their frame networks provide. So why are they concerned? Because they're being asked to deploy increasingly complex applications over their data networks, and data transport technology has had to keep pace with and even anticipate the needs of tomorrow's networking environment.

This becomes a significant challenge for companies that want to expand the Virtual Private Networking (VPN) functionality of their existing Frame Relay (FR) networks. By establishing shared access to Internet Protocol (IP) applications such as e-mail and Enterprise Resource Planning packages, the complexity associated with deploying and maintaining large, meshed Frame Relay networks has increased dramatically. Extending the network reach to include extranets, which allow network access to suppliers, distributors, and remote workers, presents yet another set of unique challenges.

This is no small issue, especially since FR continues to enjoy a healthy growth curve. In fact, FR services grew approximately 48 percent from 1998 to 1999, according to Distributed Networking Associates, a network consulting firm in Greensboro, NC, that surveys the market each year on behalf of the Frame Relay Forum.

Also, since IP has become the protocol of choice, enterprise networks have found that decentralized processing may significantly enhance network reach and load balancing. But with decentralization comes intricate network meshing that's putting a strain on customer premise equipment to provide efficient transport. Corporations are realizing that if they can reduce "meshiness," they can reduce the complexity of building, administering, and programming their networks.

One way to do this is by using an advanced IP routing method based on Multi-Protocol Label Switching (MPLS) in conjunction with Frame Relay. This approach can help corporations reduce the strain on their network equipment, support personnel, and their pocketbooks. MPLS uses the intelligence of IP routing technology to establish route assignments, but also can use the high performance of Asynchronous Transfer Mode (ATM) to transport the IP packets. It does this by mapping IP addressing and routing information directly to ATM or FR switching tables, avoiding more IP address lookups. By lowering the number of stops the packet has to make, FR networks can improve performance, reduce the complexity of network routing, and provide cost savings.

MPLS, IP, AND FRAME
MPLS technology can be integrated in the FR architecture, so it can be easily accessed through a Permanent Virtual Circuit (PVC). So what? Well, consider this example: To be fully meshed, a 25-node Frame Relay network requires 300 PVCs. With an IP-enabled FR network, that same 25-node FR network only requires 25 PVCs for IP communications. Companies running IP applications that need any-to-any connectivity can now establish a simplified, fully meshed network and provide transport for legacy protocols across traditional FR PVCs, adding new value to their networks without the need for equipment upgrades.

The performance aspects of using MPLS are also a plus. First, round trip delays are similar to traditional Frame Relay metrics on networks using closed-loop architecture. There’s also the added benefit of reducing the latency associated with CPE addressing at the network edges. End-to-end priority or true Quality of Service can also be administered through the use of multiple PVCs and priority queuing.

It’s also possible to preserve security and privacy features when using an FR network for IP VPN capabilities. By IP-enabling the PVCs in the network, the network can be logically segmented into a unique VPN, which isolates data and provides high security. On top of VPN security, every packet that arrives from an IP-enabled PVC can be equipped with an additional, private ID to protect against potential forms of network attack. Before the network switches the packet to its destination, it verifies that the terminating location is part of the same VPN ID group. By using PVCs as the basis for establishing the VPN segmentation, a corporation can virtually eliminate the threat of security attacks.

CASE IN POINT
Although this is only one approach to enabling the Enterprise VPN, several industries already are investigating it as a viable option for extending the life of their FR networks. Among them are the medical, insurance, engineering, and retail industries.

Jim Wiggins, director of technology services at Earth Tech, an environmental engineering arm of Tyco International, has integrated EarthTech’s FR network with an SMDS (Switched Multimegabit Data Service) network without losing functionality.

SMDS is a public, packet-switched service aimed at enterprises that need to exchange large amounts of data with other enterprises over the wide-area network on a non-constant or bursty basis. SMDS is connectionless, meaning that there is no need to set up a connection through the network before sending data. This provides bandwidth on demand for the bursty data transmission typically found on LANs.

“After a recent merger, I inherited a 50-location SMDS network,” Wiggins explained. “SMDS provided ‘any-to-any’ connectivity and frame didn’t. So, I initially thought my only choice was to move the frame network to SMDS. But SMDS is a dead-end technology. With an IP-enabled Frame Relay network, I can now move all the SMDS locations to frame.

“One added benefit,” Wiggins said, “is some of the preliminary performance measurements show I’m getting a major performance boost from my existing frame locations. There was a lot of tandem routing in my frame network because of the deployment of regional hubs. All traffic went through one or more regional hubs before reaching its final destination. This was causing end-to-end delays in the 200 milliseconds range. With the elimination of tandem routing, I’ve seen network delays between satellite locations drop to about 40 milliseconds.

“EarthTech’s network is now well-equipped to evolve as our business needs evolve,” Wiggins said. “We’ve overcome today’s networking challenges and are planning for the networking environment of the future.”

Joe Lueckenhoff is vice president of AT&T Data Network Services. AT&T is a leading provider of voice and data communications, with more than 80 million customers, including businesses, government, and consumers. AT&T is a supplier of data and Internet services for businesses and a national direct Internet service provider to consumers. For more information, please contact Kate Rankin at [email protected], or visit AT&T’s Web site at www.att.com

Access Line: A communications line (i.e., a circuit) interconnecting a frame-relay-compatible device (DTE) to a frame-relay switch (DCE).

Access Rate: The data rate of the user access channel. The speed of the access channel determines how rapidly (maximum rate) the end user can inject data into a frame relay network.

Backward Explicit Congestion Notification (BECN): A bit set by a frame relay network to notify an interface device (DTE) that congestion avoidance procedures should be initiated by the sending device.

Burstiness: Data that uses bandwidth only sporadically. During pauses, channels are idle and no traffic flows across them in either direction.

Channel Service Unit (CSU): A device needed to adapt the V.35 interface on a frame relay DTE to the T1/E1 interface on a frame relay switch. The T1/E1 signal format on the frame relay switch is not compatible with the V.35 interface on the DTE: therefore, a CSU or similar device, placed between the DTE and the frame relay switch, is needed to perform the required conversion.

Committed Burst Size: The maximum amount of data (in bits) that the network agrees to transfer, under normal conditions, during a time interval.

Committed Information Rate (CIR): The committed rate (in bits per second) at which the ingress/egress access interfaces of a frame relay network transfer information to the destination frame relay end system under normal conditions. The rate is averaged over a minimum time interval.

Discard Eligibility (DE): A user-set bit indicating that a frame may be discarded in preference of other frames if congestion occurs, to maintain the committed quality of service within the network.

End Device: The ultimate source or destination of data flowing through a frame relay network, sometimes referred to as a Data Terminal Equipment (DTE). As a source device, it sends data to an interface device for encapsulation in a frame relay frame. As a destination device, it receives de-encapsulated data from the interface device.

Forward Explicit Congestion Notification (FECN): A bit set by a frame relay network to notify an interface device (DTE) that congestion avoidance procedures should be initiated by the receiving device.

Frame-Relay-Capable Interface Device: A communications device that performs encapsulation. Frame-relay-capable routers and bridges are examples of interface devices used to interface the customer’s equipment to a frame relay network.

Frame Relay Frame: A variable-length unit of data in frame relay format that is transmitted through a frame relay network as pure data.

Interface Device: Provides the interface between the end device(s) and a frame relay network by encapsulating the user’s native protocol in frame relay frames and sending the frames across the frame relay backbone.

Permanent Virtual Circuit (PVC): A frame relay logical link, whose endpoints and class of service are defined by network management. Analogous to an X.25 permanent virtual circuit, a PVC consists of the originating frame relay network element address, originating data link control identifier, terminating frame relay network element address, and termination data link control identifier.

Statistical Multiplexing: Interleaving the data input of two or more devices on a single channel or access line for transmission through a frame relay network.

(Abridged definitions courtesy of the Frame Relay Forum. For a more complete listing of Frame Relay terms and definition, please visit their online glossary.)