Blazing new trails with Gigabit Ethernet

Jan 1st, 1999

Blazing new trails with Gigabit Ethernet

The new 1-Gbit/sec standard offers an evolutionary approach to increasing the capacity of existing networks based on a new generation of component technology.

Martin Wischhusen

The door to Gigabit Ethernet`s commercial implementation is now wide open thanks to the IEEE 802 commitee`s approval of standard P802.3z. The timing could not be better. Current industry estimates show Internet backbone data traffic is growing at 1000% per year, with a current volume now equaling that of voice traffic. Just a few years from now, Internet data traffic will account for 99% of all traffic, with voice supported as Internet protocol (IP) packets in the background. Users are hungry for data. Now they want the bandwidth to get it fast at the desktop.

While the technology is robust enough for use in wide area networks (WANs), Gigabit Ethernet will see initial deployment in the local area networks (LANs) of campuses and buildings. Here it will supply the bandwidth necessary to carry the growing volume of information between the routers, switches, hubs, repeaters, and servers populating the network backbone. Sophisticated applications will run better and be able to process the rapidly converging streams of raw data, video, and other mixed-media much more efficiently.

From a financial perspective, Gigabit Ethernet is the next logical networking choice for IT managers seeking to maximize their current investment. It is cost-effective, scalable, and fully backwards-compatible with its predecessors, 10Base-T and 100Base-T Ethernet, which are used in more than 80% of today`s LANs. While Asynchronous Transfer Mode (ATM) protocols carried over Synchronous Optical Network (SONET)-based networks still dominate in WANs, ATM would need to emulate Ethernet efficiently to displace it in the LAN. Conversely, Gigabit Ethernet is beginning to make inroads into metropolitan area networks as quality-of-service standards begin to solidify.

In bringing greater bandwidth to the desktop, where 10Base-T and 100Base-T connections are ubiquitous, Gigabit Ethernet wins again. It offers a seamless and natural upgrade path for existing installations since the same data frame format is used and full-duplex operation is provided. As a result, the current investment in equipment, management tools, and training methodologies are preserved.

Gigabit Ethernet and IP

Gigabit Ethernet systems that utilize IP routing and management can offer even bigger benefits. They support the shift to 80%/20% backbone/workgroup traffic ratios and offer a 10¥ throughput increase relative to current routers via Level 3 switching. Lower-rate traffic streams can be aggregated into gigabit-per-second channels that offer increased throughput at a lower cost than 622-Mbit/sec ATM/SONET implementations. This class of Gigabit Ethernet system can also support packetized voice traffic by over-provisioning bandwidth and adding frame prioritization on the fly.

Over time, as price/performance ratios decrease, the high-performance networking that Gigabit Ethernet offers will be able to reach out and touch the desktop. Traditional fiber cabling runs used on the backbone can be extended to the wiring closets within departments and workgroups. Thanks to a new generation of small-form-factor (SFF) optical connection systems now on the market, greater equipment packing density can be achieved. To maximize the current investment in copper cabling, Gigabit Ethernet will be supported by links up to 100 m over existing Category 5 unshielded twisted-pair cable (see "Will high-speed copper blunt fiber`s Gigabit Ethernet edge?" on page 37). Thanks to these advances, Ethernet will remain the de facto standard on the desktop.

Component technology speeds evolution

Several key factors at the component level are contributing to Ethernet`s rapid evolution, including shrinking sizes, lower power consumption, and faster performance. Advances in semiconductor processes, especially lithography, allow vendors to create better, faster, smaller, and lower-cost building blocks for networking OEMs. Semiconductors with 0.35-, 0.25-micron, and smaller geometries are becoming available in quantity, and the race is on toward 0.18-micron and smaller line widths. As a result, enabling technologies such as the laser sources required for optical transceivers have become much faster while at the same time requiring less power.

For example, vertical-cavity surface-emitting lasers (VCSELs) used in 1000Base-SX Ethernet can now support transmissions up to 275 m with worst-case 200 MHz-km modal bandwidth, 62.5-micron multimode optical fiber. Fabry-Perot (FP) lasers operating at 1300 nm and used in 1000Base-LX Ethernet can drive multimode optical fiber to 550 m and singlemode optical-fiber transmissions up to 5 km and beyond. For copper links, 1000Base-CX Ethernet defines connections up to 25 m over Twinax cable.

With advances in packaging technology, next-generation Gigabit Ethernet optoelectronic devices are available in dimensions that are half the size of existing SC-duplex interfaces. These SFF transceivers, based on such connectors as the MT-RJ, double fiber-optic port densities when compared to existing interfaces and have similar port spacing to copper systems, enabling more fiber-optic bandwidth on a given Ethernet system blade. These SFF transceivers also reduce overall network equipment costs by better utilizing the silicon that they interface with. For example, the quad serialize-deserialize physical-layer ICs that support four channels can be fully utilized in Gigabit Ethernet board designs due to the increased port density of SFF transceivers.

These next-generation transceivers operate at 3.3V, which ensures that overall power and heat budgets are not affected by the higher port count on a given system blade, when compared to existing transceivers that typically operate from a 5V supply. Due to their smaller size and optical aperture, the SFF transceivers also offer exceptional electromagnetic interference performance--an important consideration when designing with high frequencies associated with Gigabit-speed systems (see photo on page 50).

Next-generation Ethernet systems are already being explored based on the foundation of Gigabit Ethernet. Alternatives to current optical-link technology are under development that deliver both parallel and serial transmission of aggregated Ethernet data streams. These approaches may capitalize on wavelength-division multiplexing and advances in laser photonics and silicon processes to transport multiple channels on a single optical fiber. Potentially, these next-generation devices could be based on the SFF interface and package style. This would continue the industry`s drive to higher-bandwidth, lower-cost optoelectronic components that will support future requirements of multi-Gigabit Ethernet transmission rates.

Rapid market deployment

The near-term migration to Gigabit Ethernet will most likely follow the logical progression of its predecessors. Initially, switch-to-switch connections will be upgraded. Then will come switch-to-server connections providing desktop users with faster access to application and file servers. In installations with Fiber Distributed Data Interface (FDDI) backbones, upgrades can be made by installing an FDDI or Ethernet switch to FDDI switches and routers using Gigabit Ethernet switches or repeaters. For the lucky few, high-performance desktop implementations will include Gigabit Ethernet NICs for hot connections to Gigabit Ethernet switches or repeaters.

The fact that Fibre Channel is complementary to Gigabit Ethernet, both from a performance and cost standpoint, also should speed Gigabit Ethernet deployment. Fibre Channel is used to support 1.0625-Gbit/sec connections to network storage systems and employs encoding/decoding ICs and optical components similar to those used in Gigabit Ethernet products (see "Broadcast companies embrace Fibre Channel over fiber" on page 65).

Quality of service

Work is underway in the IEEE 802.3 standards body to address the current quality-of-service issues associated with Gigabit Ethernet. When those issues are resolved, and with a continuation of the aggressive industry move to IP-based public telecommunications networks, Gigabit Ethernet is likely to increasingly penetrate as the network of choice in metropolitan area networks.

The ongoing need for greater bandwidth and a cost-effective scalable networking solution drove the adoption of the IEEE 802.3z Gigabit Ethernet standard. With it, comes an existing Ethernet infrastructure that will remain intact well into the foreseeable future. IT managers will be able to leverage their company`s existing investment in technology, methodology, and training. User applications will flourish by being able to take full advantage of the converging data types processed by today`s real-world applications. For systems network hardware developers, the faster, smaller, and affordable building blocks that can bring it all together are on the shelf now. u

Martin Wischhusen is business planning manager, Fiber Optic Communications Div. at Hewlett-Packard Co. (Palo Alto, CA).

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