STRUCTURED CABLING: Ethernet All the Way

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The IEEE 802.3ae standard ratified in 2002 for 10 Gigabit Ethernet represents a significant milestone in the evolution of Ethernet technology and provides a tenfold performance increase over 1 Gigabit Ethernet. While Ethernet has been dominant in the LAN, the advent of 10G Ethernet dramatically expands applications for Ethernet beyond LANs into metropolitan-area networks and WANs.

The new 10G Ethernet preserves the current Ethernet semantics, including minimum and maximum frame size, and frame format. Unlike 1 Gigabit Ethernet, however, 10G Ethernet supports full-duplex transmissions only and initially worked only with optical media. However, a standard ratified by IEEE early this year offers a choice of copper-based interfaces for 10 Gigabit Ethernet now using four twin-axial copper cable pairs, same as the one used by InfiniBand or fiber channel. Meanwhile the work on 10GBase-T to run 10 Gigabit Ethernet over twisted pair is ongoing in the industry.

The 802.3ae specification defines two sets of physical interfaces for 10G Ethernet called the LAN and WAN physical interfaces. Some of the most important LAN physical interfaces are:

10Gbase-SR - 850 nm serial interface with a range of 300 meters over multimode fiber.
10Gbase-LR - 1,310 nm serial interface with a range of 10 kilometers over single-mode fiber.
10Gbase-ER - 1,550 nm serial interface with a range of 40 kilometers over single-mode fiber.
10Gbase-CX4 – a copper based interface with a range of 15 meters.

The 802.3ae specification also includes a WAN PHY definition that operates at a data rate compatible with a payload of OC-192c SONET/SDH. The WAN PHY allows transport of Ethernet data using SONET/SDH infrastructure for Layer 1 transport, while preserving the Ethernet format at Layer 2 eliminating any protocol conversions associated in traditional Packet over SONET/SDH (PoS). The WAN PHY interfaces also provide the same distance ranges as the LAN interfaces.

Using the 10G Ethernet WAN PHY lets service providers use existing SONET/SDH add/drop multiplexers or repeaters to transport Ethernet traffic. But the 10G Ethernet WAN PHY avoids the costly aspects of the traditional OC-192c SONET/SDH, such as stringent grid laser specifications, jitter requirements and stratum clocking.

All the existing Ethernet standards, such as 802.1q for virtual LANs, 802.1p for traffic prioritization and 802.3ad for link aggregation, also apply to 10G Ethernet. This makes the deployment of 10G Ethernet simply a plug-and-play situation for most corporations and service providers with Ethernet networks.

10G Ethernet applications
In LANs, where Ethernet is dominant, the immediate application for 10G Ethernet is in the LAN backbone. With 100M bit/sec Ethernet to each desktop and 1 Gigabit Ethernet connecting the wiring closet switches to the backbone switches, 10G Ethernet provides a scalable connection between the LAN backbone switches. With processor speeds now reaching 3 GHz and beyond, coupled with the rapid price decline in Gigabit Ethernet network interface cards, which are now in the $100 range, most servers come standard with Gigabit Ethernet network interface cards. 10G Ethernet provides a scalable uplink from the data center switches that connect server farms with Gigabit Ethernet copper interfaces. Certain select enterprise verticals such as entertainment and animation are deploying Gigabit Copper to each desktop to foster faster productivity and collaboration between artists. 10 Gigabit Ethernet becomes vital for such verticals to scale the LAN backbone and network aggregation layers. In most cases, 10GBase-SR and 10GBase-LR will suffice the distance range needed for the Enterprise LAN applications.

10G Ethernet provides a scalable uplink from the data center switches that connect server farms with Gigabit Ethernet copper interfaces

In Metropolitan Area Networks or MANs, many service providers take advantage of the price/ performance and simplicity of Ethernet to provide cost-effective, scalable broadband Ethernet services. New industry organizations such as Metro Ethernet Forum (MEF) coordinate the efforts between vendors and service providers to enable mass rollout of Ethernet services to business and residential customers. Examples of Ethernet services to businesses include eLine or Point-to-Point VPN service and eLAN or multipoint-to-multipoint VPN service that offer a low-cost, simple and high-speed alternative to existing ATM or Frame Relay services.

The 10Gbase-LR and 10Gbase-ER interfaces are cost-effective 10G bit/sec options for building ring or mesh topologies in MANs. By coupling with 802.3ad-based link aggregation, metropolitan service providers get an aggregate bandwidth of up to 80G bit/sec between two metropolitan routers. Some vendors also offer proprietary innovations for rapid protection in metro ring or mesh topologies while using standards based 10G Ethernet interfaces, in addition to the new 802.1w based Rapid Spanning Tree implementations.

For WAN applications, the 10G Ethernet WAN PHY lets service providers use existing SONET infrastructure, such as SONET/SDH add/drop multiplexers and repeaters, protecting their current investment in SONET/SDH gear. Because the 10G Ethernet WAN PHY avoids many of the costly attributes of SONET/SDH, it offers a compelling alternative to traditional OC-192c SONET/SDH interfaces with much better price/performance. 10 G Ethernet WAN PHY also allows direct connection DWDM systems with OC-192c interfaces. Recently, leading research institutions created the world's longest native Ethernet connection by using 10G Ethernet WAN PHY from Japanese Data Reservoir project to the CERN research center in Geneva, Switzerland, spanning approximately 18,500 kilometers, and 17 time zones. Using the 10G WAN PHY technology, a local area network connecting computers at the University of Tokyo was extended to include computers at CERN in Geneva so that they all appeared to be on the same LAN.

While 10G Ethernet products have now been shipping since 2001, 10G Ethernet market size in worldwide revenue is expected cross $1 billion mark by 2006. Compared to 2003, the market size this calendar year is expected to quadruple to $358 million. Price per 10G Ethernet port has come down from $40,000 during the initial product shipments to $2,500 this year. Coupled with the momentum in 1 Gigabit Ethernet over copper market, 10G Ethernet is strengthening the wave of technology migration in the industry offering scalable, efficient and unified network architecture for enterprises and service providers.

Chandra Kopparapu, V-P, strategic marketing and business development, Foundry Networks