What are Gigabit Ethernet?	Presented by:	Copyright 2000�

What is Gigabit Ethernet?

Gigabit Ethernet is based on the same Ethernet standard that IT managers already know and use. One of the original network architectures, defined during the 1970s, Ethernet is now widespread throughout the world. From the first implementation of the Ethernet specification � jointly developed by Digital, Intel and Xerox � this networking technology has proven itself in terms of performance, reliability and an ever-growing number of established network installations.

Benefits of Gigabit

Gigabit Ethernet builds on these proven qualities, but is 100 times faster than regular Ethernet and 10 times faster than Fast Ethernet. The principal benefits of Gigabit Ethernet include:

• Increased bandwidth for higher performance and elimination of bottlenecks
• Broad deployment capabilities without re-wiring, using 1000BASE-T Gigabit over Category 5 copper cabling
• Aggregate bandwidth to 16Gbps through IEEE 802.3ad and Intel� Link Aggregation using Intel server adapters and switches
• Full-duplex capacity, allowing data to be transmitted and received at the same time so that the effective bandwidth is virtually doubled
• Quality of Service (QoS) features which can be used to help eliminate jittery video or distorted audio
• Low cost of acquisition and ownership

Gigabit Ethernet is a function of technological evolution in response to industry demand. It is an extension of the 10Mbps Ethernet networking standard, 10Base-T, and the 100Mbps Fast Ethernet standards, 100Base-TX and 100Base-FX (Table 1). Two benefits leading to Ethernet's longevity and success are its low cost and ease of implementation. Besides offering high-speed connectivity at an economical price and support for a variety of transmission media, the Ethernet standard also offers a broad base of support for a huge and ever-growing variety of LAN applications. It is also easily scalable from 10Mbps to systems with higher-speed 100Mbps and 1000Mbps throughput.

 

Nomenclature	Speed	Distance	Media
10BASE-T	10Mbps	100m	Copper
100BASE-TX	100Mbps	100m	Copper
100BASE-FX	100Mbps	2Km	Multimode Fiber
1000BASE-LX	1000Mbps 1000Mbps	5Km 550m	Singlemode Fiber Multimode Fiber
1000BASE-SX	1000Mbps 1000Mbps	550m 275m	Multimode Fiber (50u) Multimode Fiber (62.5u)
1000BASE-CX	1000Mbps	25m	Copper
1000BASE-T	1000Mbps	100m	Copper

In June of 1998, the IEEE approved the Gigabit Ethernet standard over fiber (LX and SX) and short-haul copper (CX) as IEEE 802.3z. The fiber implementation was widely supported. With approval of 802.3z, companies could rely on a well-known, standards-based approach to improve traffic flow in congested areas without having to upgrade to an unproven or non-standardized technology.

Gigabit Ethernet was originally designed as a switched technology, using fiber for uplinks and for connections between buildings. Since then, Gigabit Ethernet has also been used extensively in servers with Gigabit Ethernet network adapters and along backbones to remove traffic bottlenecks in these areas of aggregation.

In June of 1999, the IEEE further standardized IEEE 802.3ab Gigabit Ethernet over copper (1000BASE-T), allowing 1Gb speeds to be transmitted over Category 5 cable. Since Category 5 makes up a large portion of the installed cabling base, migrating to Gigabit Ethernet has never been easier. Organizations can now replace network adapters with Gigabit Ethernet and migrate to higher speeds more extensively without having to re-wire the infrastructure.

This is especially important in areas where existing network wiring is difficult to access, such as the utility risers typically located between floors in large office buildings. Without the new standard, future deployment of Gigabit Ethernet might have required costly replacement of cabling in these risers.

However, even with the new standard, existing cabling must meet certain characteristics. Information on how to test existing cabling destined for 1000BASE-T use, including recommended testers and other important considerations, can be found on the Gigabit Ethernet Alliance web site at www.Gigabit-ethernet.org.

It is estimated that only ten percent of existing Category 5 cabling installations will not meet the ANSI/TIA/EIA568-A (1995) standard. These installations would also not support 100BASE-TX Fast Ethernet.

Compatibility and Support

Gigabit Ethernet is fully compatible with the large installed base of Ethernet and Fast Ethernet nodes. It employs all of the same specifications defined by the original Ethernet standard, including:

• CSMA/CD protocol
• Ethernet frame or "packet" format
• Full duplex
• Flow control
• Management objects as defined by the IEEE 802.3 standard

• IEEE 802.1p Layer 2 prioritization
• ToS coding bits for Layer 3 prioritization
• Differentiated Services
• Resource Reservation Protocol (RSVP)

All of these popular Ethernet technologies, which are deployed in a variety of network infrastructure devices, are applicable to Gigabit Ethernet.

Easy 10/100/1000Mbps Migration

When looking for ways to improve performance, IT managers want to know how migrating to a new technology will disrupt the current network. They also want to know the Total Cost of Ownership (TCO) of new gear. A key factor in TCO calculation is determining whether the company's investment in existing equipment and personnel training will be protected.

Because Gigabit Ethernet is based on Ethernet technology, its migration path is consistent with the familiar path from 10Mbps to 100Mbps. Existing Ethernet and Fast Ethernet devices are compatible with Gigabit Ethernet. What's more, IT personnel are already knowledgeable about Ethernet standards. As a result, performance gains can be achieved while building on a company's current investment in infrastructure and training. Costly protocol, hardware and cabling changes can be avoided, and any disruption to the network will be minimal.

The Need for Speed

Why Organizations are Moving to Gigabit Networks

The proliferation of high-performance desktop and server processors has influenced many LAN managers to migrate their data centers and server links from Ethernet and Fast Ethernet to Gigabit Ethernet. This proliferation has been driven by the phenomenal growth of the Internet, bandwidth-hungry applications, and rich new data types such as multimedia and Voice over IP (VoIP). As Gigabit Ethernet has gained ground, most recently with the approval of Gigabit Ethernet over copper, network vendors have continued to support it with newer and more advanced products.

At the network infrastructure level, three principal factors are associated with the growth of Fast Ethernet: Higher performance network servers, an increase in users with 100Mbps desktops, and a paradigm shift to network-centric workgroup and enterprise applications. Each of these factors merits a closer look.

Server Bottlenecks

Due to increasing demands presented by powerful applications like e-Commerce, medical imaging and data warehousing, today's servers are designed to process larger files and move more data faster than ever before. For example, the 32-bit PCI bus in current Intel server architecture already pumps out data in the multi-hundred megabit range, and the new PCI-X bus architecture with up to 133MHz PCI bus speeds will readily handle Gigabit Ethernet.

These capabilities are only beneficial, however, if the network and its server connections can support equivalent levels of performance. Gigabit network adapters are needed to prevent bottlenecks from developing at mission-critical servers. In fact, the majority of high-performance LAN purchases today (Figure 1) are driven by server bottlenecks and the addition of new servers to the network.

 

Figure 1.

Source: Infonetics, 1999

More Users with 100Mbps Desktops

With the advent of Fast Ethernet technology in the second half of the 1990s, organizations became interested in providing 10Mbps network support for older computers while simultaneously supporting new, more powerful workstations with 100Mbps connections. To begin integrating this capability, many network administrators adopted a strategy of "future-proofing" the network by using 10/100Mbps-enabled adapters and devices for any new expansion required.

Future-proofing became a particularly viable strategy after Intel introduced 10/100Mbps adapters for less than the cost of regular 10Mbps cards. Today, most 10/100Mbps components cost about the same as 10Mbps-only devices, and 10/100Mbps connections are becoming standard in new PCs.

As companies grow and infrastructures are rapidly built out in response to Internet-related opportunities, more and more users are being added to existing networks. And, with the need to support bandwidth-intensive applications and Internet communications at the desktop, it is not surprising that the number of users running Fast Ethernet is also growing rapidly (Figure 2). How does this impact the use of Gigabit Ethernet? With 100Mbps bandwidth at the desktop, even greater bandwidth is required at servers and aggregation points such as switch stacks.

 

Figure 2.

Source: Infonetics, 2000

Change in Application Paradigm

Along with this growth in the number of network users, there has been a change in the way people get their work done. Several years ago, people mainly relied on the network to deliver productivity applications, such as file and print. About 80% of network activity took place on the local network segment, and 20% took place on the Wide Area Network (WAN).

A tremendous shift in this dynamic has occurred with the advent of intranets, workgroup applications such as electronic scheduling, and mainframe connectivity (Figure 3). IT managers have redesigned the LAN/WAN to accommodate this shift, and 50% of network traffic is now local while 50% travels on the WAN. The new, centralized data center model means that information often travels out onto leased-lines or the Internet in order to reach far-flung offices. This traffic must be aggregated, using high-bandwidth Gigabit equipment, before it is moved onto the WAN.

 

Figure 3.

Source: Garner Group, 11/99

Where Gigabit Ethernet is Being Deployed

As more and more desktops and workgroups migrate to Fast Ethernet, aggregated traffic typically increases dramatically at the network backbone.

To handle this traffic, all new backbone switches should offer support for 1000Mbps Gigabit Ethernet uplinks. Gigabit Ethernet switches along the backbone can be used to connect high-transaction servers and segment switches that aggregate Fast Ethernet workgroups (Figure 4). In addition to aggregation switches and uplinks, Gigabit Ethernet server adapters are required.

In a common scenario, the shift to higher speeds might occur in several phases:

• Phase I � High-performance Gigabit switches aggregate backbone traffic.
• Phase II � Gigabit Ethernet is switched and routed at the network backbone with switch-to-switch connections.
• Phase III � Greater server-to-switch bandwidth is deployed using a Gigabit switch to support Gigabit Ethernet network adapter cards, boosting server connections to 1000Mbps. Gigabit Ethernet becomes standard for high-performance workstations running bandwidth-intensive applications such as videoconferencing or scientific modeling.
• Phase IV � As PCs are replaced due to normal attrition, 10/100 are replaced with 10/100/1000 network interfaces as specified. Older switches are replaced to selectively take Fast or Gigabit Ethernet down to the desktop.

Figure 4.

Home | Search | About | Offices | Manufacturers | Products | Services | Ordering
 Data101 | Mailing | Employment | Email