Allayer Announces Industry's First
Fast Ethernet Switch Chip with Trunking

SAN JOSE, Calif., March 30, 1998 -- Allayer Communications today announced a single chip that contains all the digital circuits needed to design 100/10 Mbps Fast Ethernet switches. The full-duplex chip works with network management standards such as SNMP (Simple Network Management Protocol) and RMON (Remote Network Monitoring).

The AL100 is the first chip with trunking capability that permits a switch to make multiple connections to a server or another switch (diagram 1). The chip will make possible a new breed of switch that works with existing equipment and can provide 800 Mbps trunk connections that greatly increase network performance.

The new device also lowers the cost of Fast Ethernet Switches by providing a high integration solution that includes address resolution logic, and uses a scalable approach (diagram 2). The scalable approach allows an engineer to match the number of chips to the number of ports being designed. Switch cost is further reduced thanks to an architecture that uses SGRAMs which are more cost effective than SRAMs or SDRAMs.

The AL100 uses the patent-pending RoX (Ring of Switches) expansion bus to provide a scalable solution that allows engineers to design an 8, 16, 24 or 32 port switch. This approach eliminates the expense of using a chip with more ports than are needed. As an example, an engineer would use four AL100 chips connected via the RoX bus to design a 32-port switch.

An optional fifth device, the AL300, attaches to the RoX bus and logs network management information re-ported from each AL100 chip and forwards that information to the system CPU via an additional bus. The AL300 chip can be omitted to allow the design of ultra-low cost switches without network management capability.

According to Cheng-chung Shih, President and CEO, "The tremendous demand for low-cost, expandable networks has created a need for better networking chips. To solve this challenge we used a multidisciplined team consisting of chip and system designers to conceive a scalable architecture. Then, we went one step further and added trunking capability that boosts networking performance, and gives Network and MIS managers a building block with capability between Fast Ethernet and Gigabit Ethernet."

Trunking Capability

Trunking allows an Ethernet switch to achieve high performance network connections (up to 800 Mbps) to a system such as a server. Trunking connects up to four 200 Mbps (full duplex) Fast Ethernet ports to a server or another switch. Conventional switches can only make one 200 Mbps connection to a server.

Trunking allows a switch to achieve higher bandwidth without the need to upgrade to Gigabit Ethernet equipment. Connections to a server can be simply made by adding more network interface cards.

Expansion Capability

The scalable RoX bus is also important because it can be extended via an external connector to make stackable or expandable switches (diagram 3). Stackable switches allow networks to expand without the need to discard existing equipment. For example, instead of discarding two 8-port switches, they can be stacked to form a 16-port switch without any performance degradation.

SGRAMs Lower Switch Costs

The AL100 is the first Fast Ethernet switch chip to minimize system cost by using a single SGRAM (Synchronous Graphic Random Access Memory) for buffering data. The chip's SGRAM interface allows engineers to take advantage of the lower prices resulting from the use of these chips in high-volume graphics applications.

The SGRAM with its 32-bits (wide) by 256 Kbits (deep) organization is the perfect "no compromise" solution for buffering network data which needs a wide bus for fast access. Other switch chips use memories such as SRAMs or SDRAMs which raise switch cost. For example, buffers using SDRAMs require a multiple chip solution because they are not available in affordable 32-bit widths.

RoX Bus Provides Scalability

The RoX bus allows an engineer to scale the number of chips to match the number of ports. As more ports are needed, additional chips are attached to the RoX bus. The RoX bus is also used to relay information to the AL300 Network Management Chip.

The bus, which is patent-pending, uses a 32-bit data path running at 66 Mhz. This 2 Gbps data rate is effectively doubled to 4 Gbps since each chip is simultaneously transmitting and receiving. The high-speed of the bus allows it to connect chips without any degradation in performance.

Other Features

The AL100 includes auto negotiation which automatically drops the transfer speed to 10 Mbps when it needs to talk to 10Base-T connections. The chip includes VLAN (Virtual LAN) support and flow control that conforms to the 802.3X IEEE standard. The chip also supports security such as broadcast storm control and offers port mirroring. Configuration information (e.g., trunking parameters, flow control, fixed address, etc.) is stored in an attached EEPROM (diagram 4).

AL300 Management Chip

The AL300 uses the RoX bus to collect network management information from the AL100 devices. The chip manages up to 32 Fast Ethernet ports and provides Spanning Tree Support. It provides all the MIB (Management Information Base) statistics required to support both SNMP and RMON. The device contains on-chip buffers that hold network packets until they are reported to (and from) an attached CPU.

Availability and Price

The AL100 network switch is sampling in April with production slated to begin in June. The chip is priced at $100 in a 352-pin BGA (Ball Grid Array) in quantities of 1,000.

The AL300 management chip is sampling in May with production in July. It is priced at $60 in a 240-pin PQFP (Plastic Quad Flat Pak) in quantities of 1,000.

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