Saving money with media conversion

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Media converters are useful for more than just hooking legacy equipment to new fiber networks.

CHERI PODZIMEK, Transition Networks

Increasing network complexity and the growing number of nodes on the network are accelerating the trend to higher data rates and forcing longer distance requirements into the local area network (LAN). This trend is extending the LAN into the metropolitan area network and beyond, as well. In fact, different industry reports predict that, at least for the foreseeable future, the demand for network capacity will continue to triple every year.

This level of demand is the driving force toward the use of fiber-optic cabling. Analysts estimate the market for optical-based networking equipment will reach more than $15 billion by 2003. Th Acf1eb

Media conversion is a technology that allows the use of fiber where and when it is needed, effectively integrating new equipment and media types into your existing cabling network. Traditionally, media converters have been viewed as a tactical add-on-a means of integrating an existing non-fiber-based device into a new fiber-optic cabling plant. Leveraging the investment made in the existing infrastructure is an important cost-saving advantage that media converters offer and one that has saved network designers and architects billions of dollars.

Yet, media conversion goes far beyond that environment. With media conversion you can cost-effectively install new networks, implementing fiber where and when you choose.

To understand more completely the full potential for media conversion, let's look briefly at how a media converter works. Put simply, media converters make one cable "look" like another cable-without changing the nature of your network. In its simplest form, a media converter is a small device with two media-dependent interfaces and a power supply. It can be installed almost anywhere in a network environment to expand the network designer's options. Th 0006lwfea08f1

Figure 1. The use of 100Base-SX media converters allows a smooth migration from a legacy network to a fiber-based Fast Ethernet network. The first step is installing the fiber, the media converters, and a 100Base-SX NIC in the server. The new NIC provides auto-negotiation, so no other hardware needs to be replaced.

The style of connector accepted by the converter depends on the selection of media to be converted by the unit. For example, in a Fast Ethernet environment, a 100Base-TX-to-100Base-FX media converter connects a 100Base-TX twisted-pair device to a 100Base-FX-compliant singlemode or multimode fiber port that has an ST, SC, or small-form-factor (SFF) (e.g., MT-RJ or LC) fiber-optic connector. Or in the example of Gigabit Ethernet, a media converter is commonly deployed to convert multimode-to-singlemode fiber.

Media converters are as simple to install as patch cables and connectors. Media converters function as physical-layer devices. As such, they do not interfere with any upper-level protocol information, allowing them to support both quality of service (QoS) and Layer 3 switching.

Overall, network designers can look to media conversion to provide more choice, enable the strategic location of fiber, and save money.

To achieve the profitability required by their shareholders and investors, switch and router manufacturers are forced to provide only the fiber choices that will appeal to the majority of their customers or that push the envelope of technology. As a result, you will see fiber offerings from these manufacturers at the Fast Ethernet level and above and generally only in multimode fiber.

Media conversion provides the ability to support a mixed-media environment, such as teaming coaxial cable (whether for Ethernet, RS-232, or IBM 3270 environments) with fiber. Also, singlemode can be mixed or matched, even at the Ethernet level, with multimode requirements. As an example, there currently is not a commercially available Ethernet singlemode switch on the market, yet thousands of singlemode Ethernet points are being deployed by Internet service providers as they deliver Internet data over Ethernet.

Like their copper cousins, fiber hubs, switches, and routers are provided in both stackable and chassis styles. The stackable option offers a better price point, but network designers lose the flexibility of designing their port configuration to specific requirements. But in all environments, network designers will be hard taxed to design a network without having wasted or unused fiber ports. Salespeople for these electronics manufacturers sell this situation as "upgradability," while in reality it's nothing more than buying more than what you need.

For example, say your objective is 12 fiber ports and you've chosen a 3Com 3300 for its price point and functionality. The 3300 is provided in a 12-port copper or an 8-port fiber configuration. To achieve 12 ports of fiber, you will need to buy two 8-port fiber switches, providing a total of 16 fiber ports, 25% more than what you need. However, if you bought a 12-port copper switch, you could get exactly the fiber count you need by teaming the copper switch with media-conversion technology.

Media conversion isn't just about choice, it's also about saving money. Let's examine the cost implications of meeting our objective of providing 12 ports of fiber using estimated street prices. As the numbers in Table 1 illustrate, teaming media conversion with the copper switch saves the customer nearly 50%!Th 0600 Pg162 Table2

Media conversion offers substantial price savings at the enterprise level, as well. Considering the cost implications of a 96-port fiber installation, it is readily apparent that media conversion deserves strong consideration, even when all ports are utilized (see Table 2). It should be emphasized that companies like 3Com, Cisco Systems, and Nortel Networks are not inappropriately charging for their fiber stackables and blades; rather the economics of running a billion-dollar organization makes it difficult, if not impossible, to price niche fiber solutions competitively to copper. Smaller, more focused providers that are not hampered by the required economies of scale that the switch and router manufacturers experience are the dominant suppliers of media-conversion technology.

A new standard, 100Base-SX, can also save money. The standard defines an affordable migration strategy for 10-Mbit/sec copper or fiber to 100-Mbit/sec fiber using a cabling structure capable of Gigabit Ethernet speeds and beyond. For the first time, those interested in investing in a fiber infrastructure will have a road map that clearly defines how to migrate from 10Base-FL to the future.

The primary difference between 100Base-SX and 100Base-FX is in the wavelength of the light-emitting diode (LED). While 100Base-FX was written around a 1,300-nm LED to maximize transmission distance, 100Base-SX is written around an 850-nm LED. The benefit is twofold: An 850-nm LED is compatible with 10Base-FL, and it is a lower-cost device than a 1,300-nm LED. Th 0006lwfea08f2

Figure 2. When the network manager is ready to upgrade links at the desktop, a new NIC at the workstation removes the need for the standalone media converter. This fiber-based infrastructure can support upgrades to even higher speeds in the future.

So how could you use 100Base-SX products to migrate from a 10Base-T network today to a 100-Mbit/sec network using fiber that can handle all the proposed desktop networking speeds? Starting with a typical network configuration, imagine there is an existing NT server with a 10/100Base-TX network interface card (NIC) connected to a 10/100Base-TX switch, which in turn, is connected to a workstation with a 10Base-T NIC. The link to the server operates at 100 Mbits/sec, while the workstation is at

10 Mbits/sec. The migration starts by installing the fiber and media converters. Figure 1 also shows that the NIC in the server has been replaced with a 100Base-SX NIC. At this point, all the major LAN electronics are the same as they were before, and the performance has not changed.

The next step to take in migrating the network to maximize performance would be to replace the NIC in the workstation. If this NIC is replaced, then the standalone media converter is no longer needed and the workstation is connected directly to the media-converter chassis in the main wiring closet.

Even with the cost advantages of media conversion, some network analysts have shunned media conversion because they thought it added an extra point of unmanaged failure to a network. But with the advent of sophisticated enterprise-ready management platforms, media conversion is now a cost-effective manner by which to responsibly integrate fiber where and when it is needed.

Expanded enterprise management features will enable more customers to manage a larger portion of their network, thus identifying and solving potential problems quickly and efficiently. Upwards of 100 conversion ports and beyond can be managed from a single management console controllable using a graphical user interface that should enable easy identification of media-converter type and slot number occupied. Status indicators provide summary information on power status and link indicators. Backplane temperature and voltage as well as other environmental factors can be monitored.

Fiber has traditionally been relegated to the backbone and isolated to specific applications. Media conversion introduces a means by which to cost-effectively design true hybrid networks that allow network planners to use best-of-breed electronics and best-of-breed media.

Cheri Podzimek is vice president of marketing at Transition Networks (Minneapolis). She can be reached at

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