![[Tech-On!]Tech News-Straight from Asia](/english/img/06/logo1.gif){kind=logo}
[MicroTech Watch] Switch Fabrics Break Terabit Level
| Geographic Eligibility (Edition) | Medium (Click where applicable) |
|---|---|
| Hong Kong, Malaysia, the Philippines, Singapore and Thailand (English) | Magazine + e-newsletter E-newsletter only |
| India (English) | Digital magazine + e-newsletter E-newsletter only |
| Taiwan (Complex Chinese) |
Magazine + e-newsletter E-newsletter only |
| South Korea(Korean) | Magazine + e-newsletter E-newsletter only |
| Other countries/regions | E-newsletter only *Readers from other countries/regions who want to receive Nikkei Electronics Asia printed magazine may consider paid subscription. Please contact NE Asia Circulation Department for details. |
Despite the popular focus on packet processing, the central component in high-end networking equipment is still the switch fabric. The fabric switches traffic from one line card to another and must be capable of sustaining the full bandwidth of the system -- often hundreds of gigabits per second.
Most large networking OEMs have designed their own ASIC-based switch fabrics, but that is changing in next-generation equipment, for two reasons. First, the recent economic downturn has reduced funding for in-house designs. Second, a number of strong third-party switch fabrics are now reaching the market, simplifying the design of high-end equipment. Fabric products now sampling meet a range of performance points, with throughput as high as 1 terabit per second (Tbps).
Design Challenges
Many technical challenges must be surmounted to deliver this performance. The first is efficiently moving data from the line card to the switch-fabric chips, which are typically located on a separate fabric card. Thus, the data must traverse the backplane. A terabit fabric that supports 128 full-duplex ports of 10Gbps each and 2x "overspeed" might need to handle up to 5Tbps. Using standard 500MHz signaling, this backplane would need more than 10,000 traces.
Instead, most fabrics use high-speed serdes (serialize/deserialize) circuits operating at up to 3.125Gbps. At this rate, a 5Tbps backplane can be built with a manageable 1,600 data signals. Running 3.125Gbps through connectors and across a backplane is difficult, to say the least, but fabric vendors must have the analog design skills to accomplish this feat.
A switch fabric must also deliver scalable performance. Although a carrier might want a system capable of supporting up to 128 ports, it most likely will order the system with 32 ports (or fewer) initially installed. Ideally, such a system would ship with a single fabric card supporting 32 ports, with additional cards available as field upgrades. If the maximum fabric configuration is needed even for relatively few ports, the system will be too expensive for typical port counts.
Another key issue is redundancy. High-end networking equipment is typically used at the core of a network; if such a system stops working, the entire network can go down. For this reason, carriers are demanding that equipment provide duplicate, or redundant, components that can take over in the event of a hardware failure. Switch fabrics must be designed with redundant chips and serial links. They monitor the operation of each device and quickly switch to a backup if they detect a problem. Using these techniques, the system continues to function when cards fail or are removed for maintenance.
Product Choices
Despite the technical hurdles, many companies are now developing switch fabrics for commercial use. The leading vendors are Agere, AMCC, IBM, and Vitesse.
AMCC recently sampled the first true terabit fabric, the nPX5800, which is based on technology from Yuni, a startup AMCC acquired last year. Agere plans to surpass this product with the Pi40, a 2.5Tbps fabric due to sample in Q2 of this year. The Pi40 offers excellent scalability down to 320Gbps and below, making it a strong contender for OC-192 and 10-Gbit Ethernet designs.
IBM and Vitesse have strong products for OC-48 systems and OC-192 systems with up to 320Gbps of throughput. Although these products do not deliver leading-edge performance, they meet the needs of the vast majority of systems. We expect these four companies to continue to be popular despite competition from startups such as Erlang, PetaSwitch, Tau, and several others.
Many of these fabric vendors also provide network processors, line interface chips, and other networking silicon. In addition to the large players, startups such as Internet Machines, Paion (a Korean company), TranSwitch, and ZettaCom complement their fabrics with various line card devices. Now, commercial switch fabrics provide the final piece of the puzzle, enabling even high-end networking equipment to be built entirely without ASICs. Even small startups can now compete with Cisco, Nortel, and other large companies.
by Linley Gwennap
(April 2002 Issue, Nikkei Electronics Asia)
Most large networking OEMs have designed their own ASIC-based switch fabrics, but that is changing in next-generation equipment, for two reasons. First, the recent economic downturn has reduced funding for in-house designs. Second, a number of strong third-party switch fabrics are now reaching the market, simplifying the design of high-end equipment. Fabric products now sampling meet a range of performance points, with throughput as high as 1 terabit per second (Tbps).
Design Challenges
Many technical challenges must be surmounted to deliver this performance. The first is efficiently moving data from the line card to the switch-fabric chips, which are typically located on a separate fabric card. Thus, the data must traverse the backplane. A terabit fabric that supports 128 full-duplex ports of 10Gbps each and 2x "overspeed" might need to handle up to 5Tbps. Using standard 500MHz signaling, this backplane would need more than 10,000 traces.
Instead, most fabrics use high-speed serdes (serialize/deserialize) circuits operating at up to 3.125Gbps. At this rate, a 5Tbps backplane can be built with a manageable 1,600 data signals. Running 3.125Gbps through connectors and across a backplane is difficult, to say the least, but fabric vendors must have the analog design skills to accomplish this feat.
A switch fabric must also deliver scalable performance. Although a carrier might want a system capable of supporting up to 128 ports, it most likely will order the system with 32 ports (or fewer) initially installed. Ideally, such a system would ship with a single fabric card supporting 32 ports, with additional cards available as field upgrades. If the maximum fabric configuration is needed even for relatively few ports, the system will be too expensive for typical port counts.
Another key issue is redundancy. High-end networking equipment is typically used at the core of a network; if such a system stops working, the entire network can go down. For this reason, carriers are demanding that equipment provide duplicate, or redundant, components that can take over in the event of a hardware failure. Switch fabrics must be designed with redundant chips and serial links. They monitor the operation of each device and quickly switch to a backup if they detect a problem. Using these techniques, the system continues to function when cards fail or are removed for maintenance.
Product Choices
Despite the technical hurdles, many companies are now developing switch fabrics for commercial use. The leading vendors are Agere, AMCC, IBM, and Vitesse.
AMCC recently sampled the first true terabit fabric, the nPX5800, which is based on technology from Yuni, a startup AMCC acquired last year. Agere plans to surpass this product with the Pi40, a 2.5Tbps fabric due to sample in Q2 of this year. The Pi40 offers excellent scalability down to 320Gbps and below, making it a strong contender for OC-192 and 10-Gbit Ethernet designs.
IBM and Vitesse have strong products for OC-48 systems and OC-192 systems with up to 320Gbps of throughput. Although these products do not deliver leading-edge performance, they meet the needs of the vast majority of systems. We expect these four companies to continue to be popular despite competition from startups such as Erlang, PetaSwitch, Tau, and several others.
Many of these fabric vendors also provide network processors, line interface chips, and other networking silicon. In addition to the large players, startups such as Internet Machines, Paion (a Korean company), TranSwitch, and ZettaCom complement their fabrics with various line card devices. Now, commercial switch fabrics provide the final piece of the puzzle, enabling even high-end networking equipment to be built entirely without ASICs. Even small startups can now compete with Cisco, Nortel, and other large companies.
by Linley Gwennap
(April 2002 Issue, Nikkei Electronics Asia)
