Netlink demonstrates the value of frame relay PVC prioritization for SNA traffic; Testing shows dramatic impact on SNA response times and throughput
FRAMINGHAM, Mass.–(BUSINESS WIRE)–June 3, 1996– Netlink announced today that a recently completed test program has demonstrated the benefits of PVC prioritization in delivering consistently excellent service levels for SNA applications over frame relay. The test program measured SNA response times and application throughput over a frame relay network, consisting of StrataCom frame relay switches, that was simultaneously carrying high volumes of LAN traffic. The impact of PVC prioritization, implemented in both StrataCom switches and Netlink access devices, was to improve SNA application throughput by over 60 percent and to reduce SNA response times by a factor of ten.
StrataCom frame relay switches utilize the company’s Priority PVC Class of Service to provide prioritization of PVCs (permanent virtual circuits) across the frame relay backbone network. Netlink access devices include the SafeLinx traffic management scheme, which extends prioritization to the customer premise. End-to-end PVC prioritization significantly improves application throughput and response times, thereby delivering major benefits to end users and telecommunications service providers. For end users, it assures them that SNA service levels will be maintained or improved as they migrate from leased lines to multi-protocol frame relay networks. For carriers, it provides a source of competitive differentiation by allowing them to offer superior service to networks with SNA traffic.
According to analyst Christine Heckart of TeleChoice, Inc. (Claremore, OK), “As frame relay applications become more complex, there will be a growing need to implement schemes such as Priority PVC within frame relay networks. As this test demonstrates, in a logical mesh network carrying high volumes of LAN traffic, the implementation of PVC prioritization can dramatically improve service quality for SNA users. These service quality improvements translate into cost savings for network users by reducing the access bandwidth required to achieve the desired response time and application throughput.”
“Netlink believes that the migration of SNA traffic to frame relay represents the largest opportunity for the growth of the frame relay market in 1996 and beyond,” says Roger Walton, vice president of marketing at Netlink. “Given the high importance that SNA networks place on service levels, PVC prioritization will have a critical role to play.”
For an access device, the key requirements in supporting PVC prioritization are the ability to maintain multiple output queues per PVC, strict management of data transmission rates on each PVC, sophisticated congestion control (known as “traffic shaping”), and the ability to maintain and manage SNA sessions as network conditions change. All these requirements are part of SafeLinx, the traffic management scheme employed by Netlink access devices. Based on a high-performance, RISC-based platform, Netlink access devices have the performance required to translate these capabilities into consistently excellent SNA service levels in a multi-protocol environment.
The Test Program
The test network, implemented in Netlink’s Framingham-based interoperability lab, consisted of two “branch sites” and one “headquarters site” interconnected via Netlink TurboFRADs to a frame relay network comprised of two StrataCom switches. The “branch site” configurations included both SDLC- and Token Ring-attached SNA terminal controllers, while the “headquarters” site configuration included an IBM ES9000 mainframe and 3745 front-end processor. All three sites also had LAN-based workstations able to generate sufficient IP traffic in the form of LAN-to-LAN file transfers to completely monopolize the frame relay access links.
PVCs were configured between “branch sites” and “headquarters,” and between the two branch sites. IP file transfers were conducted among the sites to flood the network with background traffic. Meanwhile, SNA devices at one of the “branch sites” attempted interactive access of a mainframe application at the “headquarters site,” while APPN devices on these sites tried to exchange SNA file transfers.
The test measured the response time of the interactive application, and the actual data transfer rate of the APPN file transfer, with and without Priority PVC and SafeLinx invoked. Measurements were also made on an idle network to obtain benchmarks for comparison. With Priority PVC running, the interactive traffic application was given the highest priority, the APPN file transfers the intermediate priority, and the IP traffic the lowest priority.
On the idle network, the SNA interactive application returned an average response time of about 0.1 seconds. (An application with minimal host processing time was deliberately chosen). However, with no prioritization in the network this response time climbed to about 2.7 seconds when the LAN-to-LAN IP file transfers were started. Once prioritization was engaged, the response time improved consistently to an average of about 0.2 seconds, close to that on the idle network. Thus, in this test, the combination of Priority PVC and SafeLinx resulted in a ten-fold improvement in SNA response time.
A test file of 328 Kbytes was transferred from “headquarters” to the “branch site.” Transfer rates were measured for a variety of frame sizes. For example, for 512 byte frames the following results were obtained. On the idle network, the test APPN file transfer operated at a rate of 61 kilobits per second. With no prioritization on the network, the transfer rate dropped to 37 kilobits per second when congestion from the IP traffic was introduced. Again, when prioritization was engaged, the transfer rate improved to 53 kilobits per second, an improvement of over 60% over the non-prioritized network.
According to TeleChoice’s Heckart, “These impressive results demonstrate the value of PVC prioritization, and of compatible implementations in both access devices and the network.”
Based in Framingham, Mass., Netlink, Inc. has developed the industry’s most comprehensive solution for transporting SNA and LAN traffic over frame relay and other intelligent networks. Customers can transition to faster, more effective communications technologies, knowing that data will be delivered reliably and predictability and that response times will be maintained or improved.
Performance testing overview and complete results available upon request.
Netlink, OmniLinx, TurboFRAD, NetFRAD, SafeLinx and Matrix VC are trademarks of Netlink, Inc. All other trademarks and registered trademarks are the properties of their respective owners.
CONTACT: Roger Walton Tracey Davis / Jackie Lustig
Netlink, Inc. Neva Group, Inc.
508-370-3628 617-441-4000, ext. 250 / 229
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