"A GARRETT COMMUNICATIONS APPLICATIONS NOTE"

SWITCHED P.M. PROVIDES CONNECTION BETWEEN 10Mb/s WORKSTATIONS AND 100Mb/s PCs FOR HIGH SPEED VIDEO ARCADE GAMES

THE PROBLEM

In many of today’s performance-oriented network environments, it is becoming a requirement to link together various 100Mb/s and 10Mb/s workgroups. Such a connectivity issue occurred recently at Quantum3D. Quantum3D is a leading developer of video cards that provide accelerated 3D computing power for affordable "visual reality" in video arcade games.

Increasingly, the most interesting arcade games are being played interactively among multiple players. This requires a high speed network connection among the game PCs.

Ross Smith, VP of Business Development at Quantum3D’s Santa Clara CA headquarters, wanted to find an efficient, cost effective way to provide 100Mb/s network connectivity among the company’s half-dozen networked video game demonstration computers—and also have them connected to the developers’ existing 10Mb/s Ethernet network of Sun workstations. The developers needed to easily download software to the game PCs for test and demonstration, but wanted their in-house network to be bridge-isolated from the game PC’s network to maintain the performance and integrity of both network segments.

THE SOLUTION

Smith turned to the Magnum line of Ethernet connectivity products from Garrett Communications to solve the problem. According to Smith, the Magnum line was able to offer Quantum3D an efficient and unique solution that met the company’s requirements.

The Magnum 800E 8-port Fast Ethernet Hub enabled the 100Mb network to interconnect the game PCs. The optional Switched Port Module (SPM) in the rear (configured as a switched 9th port) of the Magnum 800E provided connectivity to the developer’s 10Mb workstations. If / when the developers move to a 100Mb network, a simple manual switch on the SPM-TTX converts the bonus port into a 100Mb/s port.

The SPM-TTX (one of several Magnum Switched Port Modules available) provides a switched port on the Magnum 800E hub that is bridge-isolated from the 100Mb front ports. This results in a collision domain for the 800E hub ports separate from the collision domain connected into the SPM’s port For Quantum3D, the collision domain of the 800E hub is for the 100Mb game PCs, while the existing 10Mb collision domain of the developer’s workstations that is connected into the SPM is maintained as a separate 10Mb collision domain. Peak traffic on one of these domains will not impact the performance of the other.

For trade shows, Quantum3D is planning to use the Magnum 600ES Personal Hub Plus to provide a Fast Ethernet network for four to five game PCs. A smaller and more compact unit with only five 100Mb ports, the Magnum 600ES also has a switched port included to provide segmented 100 or 10Mb connectivity similar to the SPM-TTX.

ABOUT MAGNUM SPMs

The Fast Ethernet Magnum line includes a family of Switching Port Modules (SPMs) that can be configured with 800E and 8012E hubs to provide a segmented port for a variety of applications.

The SPM-TTX provides one RJ-45 port that is manually set for either 10Mb or 100Mb operation. The SPM-AUI has an AUI connector that can have a mini-transceiver attached for connecting to any 10Mb network media.

Magnum SPMs for fiber are also available—in both multi-mode and single-mode. The Magnum SPM-FST expands the fiber distance limits for shared 100Mb networks to the 412m maximum. Models are available with ST and SC connectors. The SPM-FDX operates in full-duplex mode, and extends the distance limits of multi-mode fiber in Fast Ethernet to 2km, providing configurability of Fast Ethernet fiber networks equal to the traditional 10Mb fiber distances. Single-mode versions can support fiber cable lengths of up to 15km for special applications.

SWITCHED PORT MODULE FILTERING AND FORWARDING

All Magnum SPMs are self-learning store-and-forward bridges. They reset the collision domain path delay value--which so often limits network configurability in Fast Ethernet environments.

The SPM’s packet filtering and forwarding decisions depend on whether the packet’s source node is internal (originates within the local Magnum unit or stack) or external (originates outside on the attached segment). When the source is internal, it is forwarded outside only if the destination address is not in the address table. When the source is external, it is forwarded inside only if the destination address is in the address table.