What's on the Market

On the low end, MicroAccess (Fremont, CA) markets an Ethernet switching hub that is in their network servers. The hub is a six-port single ISA or EISA card with 10Base-T or BNC thin-Ethernet connectors. The card makes up to 60-Mbps total bandwidth available, and you can install multiple cards in the same server. The card has a built-in SNMP agent that enables all SNMP-compliant managers, including MicroAccess' own, to manage the card. At $2499, this product is eminently affordable.

NetWorth (Irving, TX) has several Ethernet/FDDI (Fiber Distributed Data Interface) PowerPipes switching products, from the Series 3000 TriSegment Stackable hubs to the Series 6000 Switching and Network Services hubs. PowerPipes is a 12-port Ethernet hub channeled into an FDDI connection to the server. An ASIC (application-specific IC) buffers and transla tes incoming Ethernet frames into FDDI frames. Outbound packets are FIFO (first-in/first-out) buffered so that frames don't stack up on the FDDI ring. A custom ASIC handles all switching logic. List price for PowerPipes is $7495 for single-attached copper and $8995 for dual-attached fiber.

Catalyst or Cut-Through

What one firm calls a shared-memory design, another may call a shared bus. Cisco Systems (Menlo Park, CA) labels as shared memory its Catalyst product, an eight-port LAN switch designed to give 10 Mbps to each of its connections. One of the ports can be configured as an FDDI or CDDI (Copper Distributed Data Interface) link, providing a high-bandwidth pipe to a network backbone. Catalyst lists for $9600; the FDDI option is an additional $1995, while the CDDI option lists for $995.

The Catalyst has 2400 2-KB buffers (300 per port), as well as 760 for each output port. The switch copies incoming data to the input memory buffers. At the same time, it sends the packet's MAC (media acces s control) destination address or other information to the switch logic, which moves the packet from input to output buffers and then to the port.

An IDT 3081 RISC processor sends the data across a 32-bit-wide, 20-MHz proprietary bus that, with 640-Mbps bandwidth, easily handles traffic from all ports simultaneously. This data-switching mechanism is called a store-and-forward process, because once the data frame is stored, it may be forwarded or copied to any designated destination port.

An alternative is the cut-through switch. Introduced by Kalpana (Sunnyvale, CA), the cut-through switch reads only the address header and immediately transmits the frame to its destination. This reduces switching time but can allow bad packets to pass through, causing problems down the line.

MAD but Smart

Another vendor, Xedia (Wilmington, MA) uses a shared-bus architecture it calls Smartswitch in its three MAD (media access device) products. The first product, MADswitch, is a six-port Ethernet switc h with a slot for a 100-Mbps card, due later this year. This 100-Mbps connection may be Fast Ethernet, ATM (Asynchronous Transfer Mode), or FDDI. The Smartswitch architecture breaks incoming Ethernet frames into 64-byte packets or cells. You can use 512 cell buffers--enough for several Ethernet frames--for either input or output. Once the frame is converted to cells, it is transferred over the bus and the exit port, where the processor reassembles the message.

Each port has an IDT R-3000 RISC processor that handles port operations, including filtering nonvalid messages, cell reassembly, and transmission; each port can handle several different operations at once. The cell-transmission bus is a proprietary, 8-bit configuration, and Xedia has 16-, 32-, and 64-bit versions ready for the future. The MADswitch lists for just $2995, about half the price of most switched hubs.

Xedia's other products are MADswitch/PC and MADremote. At $2695, MADswitch/PC is a full-featured, single card that offers a 60-M bps ISA interface port. MADremote is an ISDN-remote Ethernet switch that can interface with four ISDN B channels at various speeds.

As with Cisco's Catalyst, these products offer SNMP software for managing switches and nodes. However, not all switches offer this capability. When you research switches, look for software that is compatible with your environment.

ForeRunner

Fore Systems (Warrendale, PA) uses a shared-bus design in the contentionless time-division architecture of its ForeRunner ASX-100 ATM switch. Rather than a high-speed backplane, this ``bus'' is just four chips that are each capable of 622 Mbps and use TDM (time-division multiplexing) to pass data. This architecture gives the switch a much greater capacity than the sum of its ports' bandwidths; the ForeRunner's switch fabric supports 2.5 Gbps of bandwidth.

Fore's switch products include on-board ForeThought software to manage call connections and ATM routing without a dedicated workstation. This saves money on install ation, provides higher performance, and offers greater reliability.

The ForeRunner will support up to 24 ATM devices or NICs (network interface cards), each transmitting at 155 Mbps. Modules for other interface speeds include 100-/140-Mbps TAXI, DS-3, and SONET (Synchronous Optical Network) OC-3. The ASX-100 also has a direct Ethernet interface and an FDDI port.

Each switch has a SPARC II RISC processor with 16 MB of RAM and a 120-MB hard drive. The processor controls bus access and sets up ATM circuits and operations. ATM permits two priorities of service, so 512 KB of buffer space at each port is configured in dual-priority RAM. Software handles setup, but data transfer occurs solely in hardware. Fore claims sub-10-microsecond latency in any data transfer, while setup takes less than 10 milliseconds. The ForeRunner ASX-100 starts at $23,995 for four ports, ranging up to a 24-port configuration for $34,000.

Multistage Matrix Switches

One area where matrix architecture may have the l ead is in its capacity to expand to super-high-density port designs--switch systems with 1000 or more ports. This type of switch will seldom be used in LAN environments but will likely prevail in central office installations.

That said, LattisCell is a multistage matrix switch with what SynOptics Communications (Santa Clara, CA) calls a parallel ATM architecture. Each LattisCell is essentially a stand-alone switch, the various models differing primarily in how the 16 ATM connectors are apportioned.

SynOptics uses a number of techniques to reduce traffic contention. First, it distributes traffic over multiple paths. The matrix switch itself runs at twice the speed of the incoming ports, so there's plenty of bandwidth for each port. Buffering is available at each switch element.

When a cell enters the switch, Connection Management software reads its header--with information on the cell's origin, destination, and priority--then sets up the ATM's virtual channel throughout the span of switche s. This software resides on a separate SparcStation that can control several LattisCell switches. The workstation only needs to be attached (via Ethernet) to a single switch; data for other switches is passed along a special ATM connector.

Prices begin at $27,950 for the 10115, a switch with 12 RJ-45 SONET/SDH connectors that support 155 Mbps over Category 5 UTP (unshielded twisted pair cable), and four ST-type (shielded-twisted) connectors for 155 Mbps over multimode fiber. The $31,950 10124-S has 16 fiber-optic ports: 12 100-Mbps ports used for 4B/5B encoding and four 155-Mbps SONET/SDH ports. Finally, the $35,950 LattisCell 10114 provides 14 155-Mbps SONET/SDH ports and two BNC 45-Mbps DS3 ports.

To link 10Base-T Ethernet to ATM, SynOptics has the $9995 EtherCell. Using the basic LattisCell architecture, the EtherCell provides 12 10Base-T ports and a single ATM port, either RJ-45 or fiber optic. This switch converts incoming variable-length Ethernet frames into fixed-length ATM cells and then handles all switching as in the LattisCell.

Token-Ring Solutions

Madge Networks (San Jose, CA) plans to introduce a token-ring switch early in 1995. This product will feature a shared-memory technology that Madge developed and Texas Instruments will manufacture and market. The device will handle switching between rings or individual nodes and provide a link to ATM or FDDI. It will offer full-duplex token-ring support, allowing a server to simultaneously send and receive 16 Mbps over the same connector. Token-ring NICs can be upgraded to full duplex via a software download; Ethernet NICs need a hardware change that would probably be as expensive as the original card.

Switching Packets and Cells

The MMAC-Plus from Cabletron Systems (Rochester, NH) provides over 500 ports of connectivity in a shared-bus design that handles both packet and cell switching simultaneously. This intelligent, fault-tolerant, modular hub has room on its backplane for up to 14 modules (connectivity or network se rvices). Connectivity modules are available for all major network protocols, while network services modules provide distributed management and computer services.

ATM cells are switched as is; for non-ATM input, MMAC uses SFPS (secure fast packet switching). The system backplane has two system management buses (SMB-1 and SMB-10), a flexible network bus consisting of two dual FDDI rings, and the dual-channel INB (internal network bus), which is based on the IEEE standard for FutureBus. Finally, there is space for a cell-transfer matrix, due in 1996. This will offer a switching fabric capable of data rates in excess of 60 Gbps.

The dual-channel INB is governed, like Fore's ForeRunner ASX-100, by TDM. Each INB data channel is 64 bits wide, runs at 40 MHz, and can sustain a data rate of 2 Gbps or a burst rate of 2.5 Gbps, for a total of up to 5 Gbps. The TDM design can insert packets or cells on the bus for point-to-point switching, while signaling and bus arbitration occur on a separate 8-bit manage ment and control bus.

The core design is powered by an Intel 960 processor. The Spectrum for Open Systems software (release 3.0) can manage networks of more than 10,000 nodes. Spectrum is compatible with Hewlett-Packard Openview for Unix and Windows, IBM Netview/6000, SunConnect SunNet Manager, and Novell NMS. Spectrum 3.0 lists for $15,000. MMAC-Plus starts at $11,500 without connection modules, which run from $3000 to $50,000; a typical average-cost-per-Ethernet connection is about $500 per port.

Fault-Tolerant Managed Switching

The LANplex 6000 is available in both four-slot and 12-slot chassis from 3Com (Santa Clara, CA). LANplex provides fault-tolerant switching, although it's less capable than Cabletron's MMAC. LANplex supports only Ethernet and FDDI; ATM modules are planned for early 1995. Current modules connect to one of three FDDI buses in the system. Future modules, including ATM, will connect directly to the High-Speed Interconnect Bus with sustained transfer rates of 3.2 Gbps.

3Com's starter kit includes the chassis, management module, power supply, and software. The management module hooks up via an integrated dual-attached FDDI backbone connection. The four-slot version is $16,073, while the 12-slot chassis kit starts at $31,900. An eight-port Ethernet switching module is $12,500. An FDDI six-port fiber module is $8500, and a 12-port FDDI module is $9950. The average price per port of the LANplex runs $1500 and up.

Forced Frame Relay

Cascade Communications (Westford, MA) offers several multiservice switches based on a common architecture. Its top-of-the-line B-STDX 9000 offers Frame Relay, SMDS, and ATM switching in a shared-bus architecture capable of data rates as high as 1.2 Gbps. If incoming data isn't Frame Relay (e.g., SNA/SLDC or X.25), the B-STDX encapsulates the data links and carries the data as Frame Relay. An Intel 960 RISC processor handles switching in each module.

B-STDX pricing starts at $30,000; a fully redundant, fully configured T3 sys tem typically runs about $160,000.