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eetimes.com
Net processor makers race toward 10-Gbit/s goal
By Linley Gwennap
EE Times
(06/19/00, 11:09 a.m. EST)
SAN JOSE, Calif. ? With several network processors emerging to handle OC-48 bandwidth, chip makers are turning their sights on OC-192 traffic, which pours in data at up to 10 Gbits/second. The first chips at this level will likely ship late next year, in time for widespread deployment of OC-192 fibers.
The winners in the race to deploy a cost-effective single-chip design for OC-192 must navigate IC process transitions, add more RISC engines and replumb for higher bandwidth all around. These 10-Gbit/s chips will probably require a shift to Rambus memory as well.
MMC Networks Inc. (Sunnyvale, Calif.), which originated the network processor market, opened the jousting by laying out a road map to a 20-Gbit/s chip (full-duplex OC-192) slated for late 2001. MMC is even claiming that other vendors will have problems scaling their architectures to match that performance level.
That company, along with Intel, Sitera (now part of Vitesse) and Agere (now part of Lucent Technologies), appears to have the most headroom in its current designs. All four should be able to deliver OC-192 network processors by the end of next year if they can execute well.
New entrant Lexra Inc. (Waltham, Mass.) also plans to ship an OC-192 network processor in late 2001. Meanwhile, IBM and C-Port ? now a subsidiary of Motorola ? have more design work to do before deploying single-chip OC-192 products.
The easiest way for network processor vendors to increase their performance is to add more RISC engines. The task of processing packets is inherently parallel, making it easy to share among many processor cores. Each core can work on a different packet, and in a high-speed router, there are plenty of packets to go around.
Adding cores is fairly easy. They are physically quite small, typically just a few square millimeters in a 0.18-micron CMOS process. At that size, vendors can pack 16 or more onto a modest-size die. Since all the cores on a particular chip are generally identical, adding more requires little design effort, although the bandwidth of the on-chip buses must be increased accordingly. Connecting more than a handful of cores generally requires an internal crossbar or switch rather than a single bus.
Adding engine muscle
From that perspective, Intel, Vitesse and MMC will have an easier time increasing their performance, since they use relatively few RISC engines now. For example, Intel's IXP1200 is built in an aging 0.28-micron fab acquired from Digital Equipment Corp. By moving the part to its 0.18-micron process, Intel could easily pack 16 RISC engines onto the die while maintaining the same cost structure as the current six-cylinder part.
Simply shoveling in more cores is good only to a point. IBM and C-Port already pack 16 RISC engines into their high-end network processors. Scaling much beyond that level stretches the bounds of an 0.18-micron process. Furthermore, with 16 or more cores, just connecting the cores consumes a significant part of the die area.
An alternative is to increase the clock speed of the RISC engines. A faster clock allows each core to handle more packets, keeping the number of cores in the processor to a more manageable level. It also reduces the latency of each packet through the processor. For those reasons, network processor vendors are looking to crank up their clock speeds.
For vendors using older IC processes, the solution can be as easy as a process shrink. For example, Intel should be able to push the IXP1200 from 200 to 400 MHz by moving to 0.18 micron. Vitesse Semiconductor Corp. (Camarillo, Calif.) should be able to match that speed by moving its Prism IQ2000 device to a 0.15-micron process.
Agere Inc. (Austin, Texas) believes it has plenty of headroom in its two-chip solution, comprised of a fast pattern processor (FPP) and a router switch processor (RSP). The initial products, due to ship this year, use a standard-cell design with a 133-MHz target clock speed. A more customized design in an 0.18-micron process could see a 50 percent speedup.
Lexra is already pushing the speedometer: At last week's Embedded Processor Forum, the company disclosed that its NetVortex processor will reach 427 MHz in a 0.15-micron process. The company is confident of achieving OC-192 performance at this speed.
In addition to the 10 Gbits/s of line bandwidth needed for an OC-192 port, a network processor must have adequate bandwidth in other areas as well. In general, the bandwidth to the switch fabric should match or exceed the line bandwidth, since nearly all the traffic from one port will be routed to another port.
IBM, Vitesse and MMC supply switch-fabric chips for their net processors. MMC has already announced plans for a 320-Gbit/s switch-fabric chip that will support several OC-192 lines in a single chassis. C-Port claims compatibility with a variety of third-party switch fabrics, including those from IBM and PowerX. To simplify this effort, the Common Switch Interface (CSIX) consortium is developing a standard switch-fabric interface. Vitesse/Sitera, IBM, MMC and C-Port are all CSIX members.
Memory requirements
Memory bandwidth must also scale, as more packet data must be moved into and out of DRAM. As a rule, a network processor memory subsystem should be able to sustain at least twice the packet bandwidth, since most packets will be stored into a DRAM queue and read back later. To allow for other DRAM accesses and for the inefficiencies of synchronous DRAM, current network processors have three to four times as much peak DRAM bandwidth as packet bandwidth.
By this rule of thumb, a full-duplex OC-192 processor should sustain at least 5 Gbytes/s (40 Gbits/s) to DRAM. Because double-data-rate SDRAM is less efficient than standard SDRAM, even a 256-bit-wide DDR memory at 266 MHz would not reach this level. Not only would such a wide interface require more than 500 pins, it would be difficult to support less than 256 Mbits using standard dual in-line memory modules.
Thus, most OC-192 processors are likely to move to Rambus. Four 800-MHz RDRAM channels can sustain 5 Gbytes/s using only about 200 pins, making it possible to use as little as 64 Mbits of memory. Other emerging DRAM technologies, such as FCRAM, may also be used.
In this regard, Vitesse is ahead of the game by integrating an RDRAM controller on its IQ2000. Most other devices are using PC100 SDRAM to reduce cost, while IBM's Rainier net processor supports 200-MHz DDR SDRAM. These other vendors will have to spend more design time integrating RDRAM in their future devices, although IBM appears willing to accept the larger pin counts required by SDRAM.
Putting it together
MMC will deliver a multichip OC-192 solution by mid-2001, followed by a single-chip design in late 2001, said director of marketing Robin Melnick. These chips will use the same RISC engines as the recently announced nP7120, MMC's third-generation net processor. The single-chip product will use six RISC engines, three times as many as the nP7120. To meet the processing requirements for OC-192, MMC will also boost the clock speed to about 300 MHz by converting from a semicustom layout to a more optimized design.
Intel will not comment on its plans, but its IXP device should make OC-192 speeds by moving from its antiquated 0.28-micron process to the 0.18-micron process the company uses for its PC processors. In a more-advanced process, a new IXP chip could contain 16 RISC engines instead of six and run at 400 MHz or better. This second-generation device is likely to appear by the second half of 2001.
Like the IXP1200, Vitesse's IQ2000 is designed for gigabit data streams, and two Vitesse chips are required for full-duplex OC-48. With only four RISC engines, the IQ2000 appears underpowered, but the chip is able to match Intel's performance through better load balancing and a more-efficient core design.
Stephen Sheafor, chief technology officer at Sitera Inc. (Longmont, Colo.), said that Vitesse's next-generation design will leap from a modest 0.25-micron process to a leading-edge 0.15- or 0.13-micron process. With a more-advanced process, the company could easily double the current clock speed and move to 12 or 16 cores, reaching the performance needed for OC-192.
For its part, IBM's Rainier was designed with OC-192 in mind, as it is somewhat overengineered for OC-42 applications, according to chief architect Chuck Sannipoli. For example, Rainier is designed for up to 8 Gbits/s of line bandwidth, well beyond what other network processors can handle.
Shrink for speed
But since Rainier is already in an 0.18-micron process, boosting the clock speed or adding more RISC engines won't be easy. IBM is relying on a shrink to 0.13-micron CMOS to boost the clock speed of the current device to 200 MHz or so. To deliver a full-duplex OC-192 solution, the company will pair two of these chips, one for upstream and one for downstream. This approach, however, will put IBM at a cost disadvantage compared with single-chip OC-192 solutions.
With 16 RISC engines, C-Port's C-5 has the most CPU power of today's crop of net processors. The company expects clock-speed improvements in the future, but extending the current architecture to full-duplex OC-192 would require 32 RISC engines at 400 MHz, which is not achievable even in a 0.13-micron process.
Instead, C-Port is working on a new device, known as the C-Y, to reach that level. Dave Husak, C-Port's chief technology officer, noted that because the C-5 is programmed in a high-level language, it could use a different microarchitecture while maintaining software compatibility through recompilation. A more-powerful RISC engine would make a 20-Gbit/s chip easier to build. Given the extent of the redesign, however, the C-Y may not be available until 2002.
Agere believes its approach with the FPP/RSP chip set makes that combination more easily scalable than competing devices. Instead of RISC engines, Agere uses more-powerful specialized compute engines, each handling a different task, and processes packets in a pipeline rather than in parallel. Thus, Agere has left it to future products to exploit packet parallelism.
Agere can reach OC-192 performance by simply setting up a second, parallel packet pipeline and raising its clock speed to 266 MHz. That speed should be achievable by a full-custom 0.18-micron version of the current standard-cell 0.25-micron design.
For its part, Lexra is a relative latecomer to this market, but it plans to deliver a 16-core version of its NetVortex processor by late 2001. At 427 MHz, this 0.15-micron chip will support full-duplex OC-192, claims chief executive officer Charlie Cheng. Because Lexra is licensing the core design, its licensees must grapple with the hard problems of supporting enough memory and fabric bandwidth to handle two OC-192 data streams.
Counting customers
MMC already counts Cisco, 3Com and Nortel among its customers. As a pioneer, MMC has had this market almost to itself, but competition is now intense, and most other network processor vendors are now backed by large semiconductor companies.
Intel is making a big thrust into networking, spending more than $2 billion to acquire Level One Communications and other network chip companies. That figure doesn't even count the $625 million spent on Digital Semiconductor, which supplied both the design and the fab for the IXP1200. When Intel makes investments of this size, it expects a sizable return.
The company claims to have 25 design wins for the IXP1200, including Nortel, Ericsson and Newbridge. The part is not as sophisticated as some of its competitors, but it is well-suited to gigabit data streams. With an OC-192 part looking quite doable, Intel stands poised to carve out a big chunk of this market.
IBM is the only major semiconductor vendor attacking the market with homegrown technology. In fact, the company has already developed a low-end chip, dubbed Charm, to complement Rainier, as well as a 28-Gbit/s switch-fabric chip to connect up to eight of its network processors.
Most high-end networking products still use custom ASICs, and IBM is the leading supplier of these ASICs. Thus, the company has already established a channel for its network processors and switch fabric. This broad product line has attracted several customers to Rainier, including Nortel, Alcatel and Asante.
C-Port, meanwhile, is integrating its application programming interfaces and development environment with its parent company's. Motorola plans to deploy a single tool set to allow customers to write C or C++ programs that run on either C-Port processors or Motorola's standard PowerPC and PowerQuicc devices.
This broad product line and reliance on high-level programming should help the C-5 become widely used; the company already claims 20 design wins, including three top-tier vendors. Because of the significant redesign, however, C-Port's single-chip OC-192 solution is likely to arrive later than those from other vendors.
Lexra's licensing strategy and ability to execute MIPS instructions give it two significant differentiators. The largest network-equipment vendors, such as Cisco and Nortel, are often hesitant to rely on a third party to deliver a key component without a second source. They also don't want to see other networking vendors using the same chips to deliver similar products. Lexra allows licensees to design their own custom components and select their own foundries, giving these giant vendors more control over their own destiny.
By acquiring Sitera, meanwhile, Vitesse added a network processor to its portfolio of physical-layer (PHY) chips and switch fabrics. But as a sugar daddy, Vitesse is not as sweet as Intel, and it lacks the networking ties of IBM and Motorola. Other than its Rambus interface, Vitesse's IQ2000 has little to distinguish itself from the competition. The company claims design wins at Quarry Technologies and Nortel, a promiscuous networking vendor that seems to be on everyone's customer list.
Competitive crowd
Now part of Lucent, Agere offers a solid OC-48 solution that should scale well to OC-192. The FPP/RSP two-piece chip set, however, is more expensive than any of the single-chip solutions. Agere claims the requisite 20 design wins, but it remains to be seen whether Lucent has the muscle to push Agere's product into a crowded marketplace.
By the end of this year, six vendors are slated to ship network processors delivering 2-Gbit or better performance. By the end of next year, several will be shipping 20-Gbit network processors. As more of these devices become available, they will turn the tide away from the hardwired ASICs that dominate high-end networking today.
"ASIC designers are always under fire from the software developers" who need the hardware to validate their code, said Steve Fu, technology partnership manager of Cisco Systems' enterprise router division. He pointed out that programmable parts improve time-to-market by allowing software to be tested earlier in the cycle.
Network-equipment makers evaluating the current processor choices should first consider performance: Intel's IXP1200 and Vitesse's IQ2000 are best-suited for dual gigabit or single OC-48 streams, while the others can handle dual OC-48 channels. If price is a concern, MMC is the leader, whereas Agere's two-chip solution seems overpriced.
Another major criterion is whether to program in a high-level language, which reduces development time, or in assembly code, which is more compact. C-Port appears to have the best compiler today, while Lexra will have strong tools support for its MIPS-based processors. Some may be concerned that Intel is the only company in the industry that is not supporting industry efforts, under the Common Processor Interface consortium, to standardize APIs.
Many OEMs prefer to ensure compatibility by obtaining their components from the same vendor. From this angle, IBM comes out on top. It has the broadest line of network processors, switch fabrics, control processors and (through its partnership with Multilink) PHY chips.
With several vendors in the processor market, networking companies have a range of innovative products to choose from, and prices should be reasonably low. No net processor vendor is likely to dominate. This competition should spur increased adoption of network processors.
? Linley Gwennap is the founder and principal analyst of The Linley Group, a technology analysis firm based in Mountain View, Calif. |
