networkZONE Products for the week of May 5, 2003
Vitesse Says…
Born To Scale - Vitesse's Integrated 24-port Gigabit
Switch IC Offers Full Features, Manageability, Quick Time-To Market, Low
BOM
Vitesse Semiconductor Corp. has released the Stapleford (VSC7303),
a 24-port, Gigabit Switch IC, intended to migrate existing 24- and 48-port,
10/100 LAN switch boxes to triple speed Gigabit capabilities. This product
is available today for production orders.
Offering wire speed performance and the ability to forward packets at 36 Million/second, this Gigabit Switch-on-Chip combines the highest level of integration and functionality in its class and simultaneously achieves a very low system cost point. Stapleford supports Jumbo packets and provides for wire speed automatic learning. Its Layer 4-aware programmable classifier allows for enhanced Quality of Service, and it is optimized with Reduced Gigabit Media Independent Interface (RGMII) and Reduced Ten Bit Interface (RTBI) to simplify board layout and condense design time. Stapleford also supports Half Duplex Back Pressure and both Multicast and Broadcast Storm Control. This 24-port Gigabit Switch IC dissipates the industry's lowest amount of power, less than five watts, which eliminates the need for external cooling elements and reduces the cost of the power supply unit.
"Vitesse has been successful in leveraging its dominant position in the WAN market into the LAN," said Kevan Smith, business unit director of Vitesse's Ethernet Products Division. "By introducing the next-generation of highly integrated, cost optimized Gigabit Switch ICs, Vitesse is enabling OEMs to aggressively replace the existing Fast Ethernet switches and take advantage of price points two-times that of Fast Ethernet prices as well as the improved performance."
Vitesse's London Family of Gigabit Switch ICs
Stapleford is a member of the London family of Ethernet switches. London
products are designed to yield Gigabit wire-speed performance at extremely
competitive prices. All members of the family have a common architecture
to ensure ease-of-use and the reusability of software (from 8- to 48 ports).
The family offers high levels of integration including optimized on-chip
memory and addressing capabilities, which eliminates the need for external
memory. Additionally, the London family has multiple controller interfaces
allowing OEMs to use a very inexpensive 8051 micro-controller to configure
the switch system for unmanaged and Web managed solutions.
Additional Features and Pricing
Stapleford comes with a complete managed reference system solution targeted
at the Desktop and Workgroup switch market. The reference platform is optimized
with only six-layers of PCB board. This switch is compliant with the following
IEEE protocols:
analogZONE Says . . .
Even with the recession still in full bloom several companies are battling for pole positions in the extremely cutthroat SOHO/SMB (Small-Medium Business) market where price rules all. The last week has seen the arrival of both Vitesse's Stapleford architecture, and a strikingly similar offering from Marvell. Although the Vitesse chip is targeted for the low-end of the managed switch market while the Marvell silicon is aimed even lower down the food chain (and even higher volume markets), they have enough things in common that they beg to be compared side-to-side. I'll try to point out these differences as we go along.
Getting back to business, Vitesse's Stapleford is a. 24-port tri-speed Gigabit switch "Layer-2+" switch, based on a scale-up of their earlier 16-port offering. The density offered is significantly higher than SwitchCore's venerable 16-port switch chip, but it does not offer full layer-3 capabilities. This represents the increasingly popular tactic of silicon providers to add enhancements to simple layer-2 chips that add value without adding too much cost. In this case the "+" means that the switch cannot do actual routing, but it can set priorities for its queues based on layer 2-4 criteria. This can be rather useful as a simple mechanism for ensuring QoS for multimedia in a workgroup or SOHO environment.
Besides the Stapleford's management features, one of the key differences between this chip and the Marvell chip DX series is its unique architecture which derives its roots from Exbit, a Danish company that Vitesse acquired a year or so ago. Rather than the normal shared-memory approach used by most low-end (and many high-end) switches, it employs something that Vitesse calls a dedicated memory architecture. This means that instead of being tied together by a common memory, the ports communicate with each other over a high-speed "frame bus." The bus runs at almost 2X (32 Gbit/s) port capacity to assure non-blocking - even with all ports fully loaded. The scheduling logic on the bus handles queuing while the actual buffering is handled at each port using a small chunk of dedicated memory in the ingress and egress queues. For a peek at how this all fits together, click here for an architectural block diagram.
Each port module has its own triple-speed MAC, ingress & egress FIFOs, and a categorization engine which inspects packet headers to layer 4. The categorization information is used to control the policing and shaping functions within the port module. This is strangely reminiscent of the bus-based architecture that TI used in its unsuccessful series of "ThunderLAN" 10/100 Ethernet switches back in the late nineties. While innovative, the chips did not scale well and ran into blocking problems because of the bandwidth limitations of the internal bus. Bus bandwidth does not appear to be a problem for this product however. Vitesse won't tell me how wide their bus is, some rough calculations show that given a nominal 150-200 MHz internal clock rate, such a thing is feasible, although I expect that the bus is terribly wide - unless they are using a DDR clocking scheme. However it is implemented, I think it will provide the performance and non-blocking characteristics so often absent in low-end chip sets. In fact, I actually had the chance to see the chip run at Networld+Interop this week and was quite impressed. We'll take a look at a few more details and then give you a taste of what I saw at the demo.
The chip is nicely featured with important things like support for jumbo frames and all 64 DifServ items. It also handles QnQ, known also as double VLAN tagging . This is especially useful since QnQ is beginning to find use in some metro systems as a "poor man's MPLS" protocol. There are also several features I am glad to see, especially in a low-end switch, such as broadcast & multicast storm control, as well as traffic policing and shaping using layer 2-4 criteria with 1 Mbit/s granularity. Another handy feature is the ability to perform any-port, any-group link aggregation, something that MIS managers will appreciate as they try to manage heavy traffic loads.
For all the bells and whistles it sports, the Stapleford chip is designed to drive the cost per port to rock bottom. It requires no external CAMs, FIFOs or significant cost-adders to deliver a full-featured product to the end-user. Vitesse says that their ready-to-run software allows management of VLANs, link aggregation, QoS, and port configuration via an in-band web-based interface using an inexpensive (around $1.25) 8051 controller. Of course, if you need more processing power for managed systems and heavy stats processing, the chip's parallel interface hooks directly to ARM7, MIPS, or PowerPC CPUs.
I got to see the $1.25 management solution running at the Vitesse demo at Networld+Interop and found it very impressive. The demo board they had running had 24 ports of tri-speed Gigabit Ethernet running under the control of an Intel 8051, which runs a Linux-based Apache Server web server. The free source code provides an in-band management channel that presents a series of menu pages that allow a novice user (like me) to turn on, configure turn off, and aggregate selected channels at will without the confusing jargon associated with managing "real" business-class hardware. You also get a limited QoS configuration menu that allows you to grant priority to any one type of traffic, such as VoIP, streaming video, or short messaging. While this software does not exploit all the functionality of the chip set it provides baseline functionality that's easy for a novice networker to use. And should you want more features, Vitesse supplies the Linux source code for you to hack around with yourself. Running the demo board I was able to easily invoke simple configuration changes, shut down or aggregate channels, and otherwise observe the chip work. I also saw an impressive example of how the QoS feature keeps priority traffic flowing even when a port is aggregated and oversubscribed with twice its maximum capacity.
While not as obvious, the switch's low power consumption (around 5 W) is also a cost-saving feature. Besides the obvious savings from using a smaller power supply you should be able to shrink, or eliminate, a cooling fan if you use one of the new generation of power-saving transceivers. Speaking of which, the device's MACs support both RGMII and RTBI (fiber) interfaces, allowing it to hook up to most PHY chips or transceivers on the market.
Vitesse has also paid close attention to time-to-market issues. Besides the aforementioned reference software you can also get a full-up reference design, complete with components lists and artwork for a validated six-layer PCB design. This and the management software I discussed earlier will cut development time and costs significantly, while not sacrificing functionality or reliability.
It seems that Vitesse's architecture allows them to easily scale from 16 to 24 ports, and perhaps a bit firther. They are planning on offering at least one more variant with even more ports, but no details are available at this time. They are also seriously talking about introducing devices with smaller port-counts towards the end of year. But regardless of port count, Vitesse has done an excellent job of delivering the benefits and performance expected of workgroup-level managed switches at a price that comes close to some unmanaged products.
Pricing for volume production is $144 per unit for the 24-port chip. If you are looking for a managed solution, the extra few dollars for the host controller and a handful of other components buys you a lot of extra functionality. Since they are sampling now, and have related product already on the market, Vitesse gets a low Vapor Index Rating for their switch chip.
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