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Black Box Explains...Gigabit Ethernet.

As workstations and servers migrated from ordinary 10-Mbps Ethernet to 100-Mbps speeds, it became clear that even greater speeds were needed. Gigabit Ethernet was developed for an even faster Ethernet... more/see it nowstandard to handle the network traffic generated on the server and backbone level by Fast Ethernet. Gigabit Ethernet delivers an incredible 1000 Mbps (or 1 Gbps), 100 times faster than 10BASE-T. At that speed, Gigabit Ethernet can handle even the traffic generated by campus network backbones. Plus it provides a smooth upgrade path from 10-Mbps Ethernet and 100-Mbps Fast Ethernet at a reasonable cost.

Compatibility
Gigabit Ethernet is a true Ethernet standard. Because it uses the same frame formats and flow control as earlier Ethernet versions, networks readily recognize it, and it’s compatible with older Ethernet standards. Other high-speed technologies (ATM, for instance) present compatibility problems such as different frame formats or different hardware requirements.

The primary difference between Gigabit Ethernet and earlier implementations of Ethernet is that Gigabit Ethernet almost always runs in full-duplex mode, rather than the half-duplex mode commonly found in 10- and 100-Mbps Ethernet.

One significant feature of Gigabit Ethernet is the improvement to the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) function. In half-duplex mode, all Ethernet speeds use the CSMA/CD access method to resolve contention for shared media. For Gigabit Ethernet, CSMA/CD has been enhanced to maintain the 200-meter (656.1-ft.) collision diameter.

Affordability and adaptability
You can incorporate Gigabit Ethernet into any standard Ethernet network at a reasonable cost without having to invest in additional training, cabling, management tools, or end stations. Because Gigabit Ethernet blends so well with your other Ethernet applications, you have the flexibility to give each Ethernet segment exactly as much speed as it needs—and if your needs change, Ethernet is easily adaptable to new network requirements.

Gigabit Ethernet is the ideal high-speed technology to use between 10-/100-Mbps Ethernet switches or for connection to high-speed servers with the assurance of total compatibility with your Ethernet network.

When Gigabit Ethernet first appeared, fiber was crucial to running Gigabit Ethernet effectively. Since then, the IEEE802.3ab standard for Gigabit over Category 5 cable has been approved, enabling short stretches of Gigabit speed over existing copper cable. Today, you have many choices when implementing Gigabit Ethernet:

1000BASE-X
1000BASE-X refers collectively to the IEEE802.3z standards: 1000BASE-SX, 1000BASE-LX, and 1000BASE-CX.

1000BASE-SX
The “S“ in 1000BASE-SX stands for “short.“ It uses short wavelength lasers, operating in the 770- to 860-nanometer range, to transmit data over multimode fiber. It’s less expensive than 1000BASE-LX, but has a much shorter range of 220 meters over typical 62.5-µm multimode cable.

1000BASE-LX
The “L“ stands for “long.“ It uses long wavelength lasers operating in the wavelength range of 1270 to 1355 nanometers to transmit data over single-mode fiber optic cable. 1000BASE-LX supports up to 550 meters over multimode fiber or up to 10 kilometers over single-mode fiber.

1000BASE-CX
The “C“ stands for “copper.“ It operates over special twinax cable at distances of up to 25 meters. This standard never really caught on.

Gigabit over CAT5—1000BASE-TX
The 802.3ab specification, or 1000BASE-TX, enables you to run IEEE-compliant Gigabit Ethernet over copper twisted-pair cable at distances of up to 100 meters of CAT5 or higher cable.

Gigabit Ethernet uses all four twisted pairs within the cable, unlike 10BASE-T and 100BASE-TX, which only use two of the four pairs. It works by transmitting 250 Mbps over each of the four pairs in 4-pair cable. collapse


Black Box Explains...Multimode vs. single-mode Fiber.

Multimode, 50- and 62.5-micron cable.
Multimode cable has a large-diameter core and multiple pathways of light. It comes in two core sizes: 50-micron and 62.5-micron.

Multimode fiber optic cable can be... more/see it nowused for most general data and voice fiber applications, such as bringing fiber to the desktop, adding segments to an existing network, and in smaller applications such as alarm systems. Both 50- and 62.5-micron cable feature the same cladding diameter of 125 microns, but 50-micron fiber cable features a smaller core (the light-carrying portion of the fiber).

Although both can be used in the same way, 50-micron cable is recommended for premise applications (backbone, horizontal, and intrabuilding connections) and should be considered for any new construction and installations. Both also use either LED or laser light sources. The big difference between the two is that 50-micron cable provides longer link lengths and/or higher speeds, particularly in the 850-nm wavelength.

Single-mode, 8–10-micron cable.
Single-mode cable has a small, 8–10-micron glass core and only one pathway of light. With only a single wavelength of light passing through its core, single-mode cable realigns the light toward the center of the core instead of simply bouncing it off the edge of the core as multimode does.

Single-mode cable provides 50 times more distance than multimode cable. Consequently, single-mode cable is typically used in long-haul network connections spread out over extended areas, including cable television and campus backbone applications. Telcos use it for connections between switching offices. Single-mode cable also provides higher bandwidth, so you can use a pair of single-mode fiber strands full-duplex for up to twice the throughput of multimode fiber.

Specification comparison:

50-/125-Micron Multimode Fiber

850-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 3.5 dB/km;
Distance: 550 m;

1300-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 1.5 dB/km;
Distance: 550 m

62.5-/125-Miron Multimode Fiber

850-nm Wavelength:
Bandwidth: 160 MHz/km;
Attenuation: 3.5 dB/km;
Distance: 220 m;

1300-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 1.5 dB/km;
Distance: 500 m

8–10-Micron Single-Mode Fiber

Premise Application:
Wavelength: 1310 nm and 1550 nm;
Attenuation: 1.0 dB/km;

Outside Plant Application:
Wavelength: 1310 nm and 1550 nm;
Attenuation: 0.1 dB/km collapse


Black Box Explains...Single-strand fiber WDM.

Traditional fiber optic media converters perform a useful function but don’t really reduce the amount of cable needed to send data on a fiber segment. They still require two strands... more/see it nowof glass to send transmit and receive signals for fiber media communications. Wouldn’t it be better to combine these two logical communication paths within one strand?

That’s exactly what single-strand fiber conversion does. It compresses the transmit and receive wavelengths into one single-mode fiber strand.

The conversion is done with Wave-Division Multiplexing (WDM) technology. WDM technology increases the information-carrying capacity of optical fiber by transmitting two signals simultaneously at different wavelengths on the same fiber. The way it usually works is that one unit transmits at 1310 nm and receives at 1550 nm. The other unit transmits at 1550 nm and receives at 1310 nm. The two wavelengths operate independently and don’t interfere with each other. This bidirectional traffic flow effectively converts a single fiber into a pair of “virtual fibers,” each driven independently at different wavelengths.

Although most implementations of WDM on single-strand fiber offer two channels, four-channel versions are just being introduced, and versions offering as many as 10 channels with Gigabit capacity are on the horizon.

WDM on single-strand fiber is most often used for point-to-point links on a long-distance network. It’s also used to increase network capacity or relieve network congestion. collapse


Black Box Explains...Link loss.

Media converters solve the problem of connecting different media types in mixed-media networks. In order to comply with IEEE standards, they implement IEEE data-encoding rules and the Link Integrity Test.

For... more/see it nowa twisted-pair segment, a link is a signal sent by the converters when the cable is in use. If no Link Integrity Test signal is received, the connected device assumes that the link is lost.

With fiber cable, a connected device checks a line by monitoring the Link Integrity Test signal from the converter and the power of the light being received. If the light’s power drops below a certain threshold, the link is lost. In either case, link loss usually results from a broken cable, which is the cause of approximately 70% of all LAN problems.

Link loss is often indicated by an LED on a connected network device. You can also monitor a link with network-management software, such as SNMP, which sends a TRAP (alert) to the management workstation when the link is lost.

Media converters actually function as two separate Multistation Access Units (MAUs). For example, one monitor is a twisted-pair segment and one monitor is a fiber segment. If a fiber cable is broken and the link is lost, a network manager on the twisted-pair end won’t know there’s a problem until users on the fiber side report it.

To solve this problem, Black Box® Modular Media Converters feature a unique Link-Loss capability. This enables the link status on one segment to reflect the link status of the other segment. So if the link is lost on the fiber side, the link is disabled on the UTP segment as well. And the converters will send an SNMP TRAP indicating the loss of link to the management workstation. collapse


Black Box Explains…Fiber Ethernet adapters vs. media converters.

When running fiber to the desktop, you have two choices for making the connection from the fiber to a PC: a fiber Ethernet adapter or a media converter like our... more/see it nowMicro Mini Media Converter.

Fiber Ethernet adapters:

  • Less expensive.
  • Create no desktop clutter, but the PC must be opened.
  • Powered from the PC—require no separate power provision.
  • Require an open PCI or PCI-E slot in the PC.
  • Can create driver issues that must be resolved.
  • May be required in high-security installations that require a 100% fiber link to the desktop.

  • Media converters:
  • More expensive.
  • No need to open the PC but can create a cluttered look.
  • Powered from an AC outlet or a PC’s USB port.
  • Don’t require an open slot in the PC.
  • Plug-and-play installation—totally transparent to data, so there are no driver problems; install in seconds.
  • The short copper link from media converter to PC may be a security vulnerability.
  • collapse


    Black Box Explains...Media converters that are really switches.

    A media converter is a device that converts from one media type to another, for instance, from twisted pair to fiber to take advantage of fiber’s greater range. A traditional... more/see it nowmedia converter is a two-port Layer 1 device that performs a simple conversion of only the physical interface. It’s transparent to data and doesn't “see” or manipulate data in any way.

    An Ethernet switch can also convert one media type to another, but it also creates a separate collision domain for each switch port, so that each packet is routed only to the destination device, rather than around to multiple devices on a network segment. Because switches are “smarter” than traditional media converters, they enable additional features such as multiple ports and copper ports that autosense for speed and duplex.

    Switches are beginning to replace traditional 2-port media converters, leading to some fuzziness in terminology. Small 4- or 6-port Ethernet switches are very commonly called media converters. In fact, anytime you see a “Layer 2” media converter or a media converter with more than two ports, it’s really a small Ethernet switch. collapse


    Black Box Explains...T1 and E1.

    If you manage a heavy-traffic data network and demand high bandwidth for high speeds, you need digital super-fast T1 or E1.

    Both T1 and E1 are foundations of global communications. Developed... more/see it nowmore than 35 years ago and commercially available since 1983, T1 and E1 go virtually anywhere phone lines go, but they’re much faster. T1, used primarily in the U.S., sends data up to 1.544 Mbps; E1, used primarily in Europe, supports speeds to 2.048 Mbps. No matter where you need to connect—North, South, or Central America, Europe, or the Pacific Rim—T1 and E1 can get your data there fast!

    T1 and E1 are versatile, too. Drive a private, point-to-point line; provide corporate access to the Internet; enable inbound access to your Web Server—even support a voice/data/fax/video WAN that extends halfway around the world! T1 and E1 are typically used for:
    • Accessing public Frame Relay networks or Public Switched Telephone Networks (PSTNs) for voice or fax.
    • Merging voice and data traffic. A single T1 or E1 line can support voice and data simultaneously.
    • Making super-fast LAN connections. Today’s faster Ethernet speeds require the very high throughput provided by one or more T1 or E1 lines.
    • Sending bandwidth-intensive data such as CAD/CAM, MRI, CAT-scan images, and other large files.

    Scaling T1
    Basic T1 service supplies a bandwidth of 1.536 Mbps. However, many of today’s applications demand much more bandwidth. Or perhaps you only need a portion of the 1.536 Mbps that T1 supplies. One of T1’s best features is that it can be scaled up or down to provide just the right amount of bandwidth for any application.

    A T1 channel consists of 24 64-kbps DS0 (Digital Signal [Zero]) subchannels that combine to provide 1.536 Mbps throughput. Because they enable you to combine T1 lines or to use only part of a T1, DS0s make T1 a very flexible standard.

    If you don’t need 1.536 Mbps, your T1 service provider can rent you a portion of a T1 line, called Fractional T1. For instance, you can contract for half a T1 line—768 kbps—and get the use of DS0s 1–12. The service provider is then free to sell DS0s 13–24 to another customer.

    If you require more than 1.536 Mbps, two or more T1 lines can be combined to provide very-high-speed throughput. The next step up from T1 is T1C; it offers two T1 lines multiplexed together for a total throughput of 3.152 on 48 DS0s. Or consider T2 and get 6.312 Mbps over 96 DS0s by multiplexing four T1 lines together to form one high-speed connection.

    Moving up the scale of high-speed T1 services is T3. T3 is 28 T1 lines multiplexed together for a blazing throughput of 44.736 Mbps, consisting of 672 DS0s, each of which supports 64 kbps.

    Finally there’s T4. It consists of 4032 64-kbps DS0 subchannels for a whopping 274.176 Mbps of bandwidth—that’s 168 times the size of a single T1 line!

    These various levels of T1 service can by implemented simulta-neously within a large enterprise network. Of course, this has the potential to become somewhat overwhelming from a management standpoint. But as long as you keep track of DS0s, you always know exactly how much bandwidth you have at your disposal.

    T1’s cousin, E1, can also have multiple lines merged to provide greater throughput. collapse


    Black Box Explains...vDSL.

    VDSL (Very High Bit-Rate Digital Subscriber Line or Very High-Speed Digital Subscriber Line) is a “last-mile” broadband solution for both businesses and homes, providing economical, high-speed connections to fiber optic... more/see it nowbackbones.

    VDSL enables the simultaneous transmission of voice, data, and video on existing voice-grade copper wires. Depending on the intended applications, you can set VDSL to run symmetrically or asymmetrically. VDSL’s high bandwidth allows for applications such as high-definition television, video-on-demand (VOD), high-quality videoconferencing, medical imaging, fast Internet access, and regular voice telephone services—all over a single voice-grade twisted pair. The actual VDSL distances you achieve vary based on line rate, gauge and type of wire, and noise/crosstalk environment. collapse


    Black Box Explains...DIN rail usage.

    DIN rail is an industry-standard metal rail, usually installed inside an electrical enclosure, which serves as a mount for small electrical devices specially designed for use with DIN rails. These... more/see it nowdevices snap right onto the rails, sometimes requiring a set screw, and are then wired together.

    Many different devices are available for mounting on DIN rails: terminal blocks, interface converters, media converter switches, repeaters, surge protectors, PLCs, fuses, or power supplies, just to name a few.

    DIN rails are a space-saving way to accommodate components. And because DIN rail devices are so easy to install, replace, maintain, and inspect, this is an exceptionally convenient system that has become very popular in recent years.

    A standard DIN rail is 35 mm wide with raised-lip edges, its dimensions outlined by the Deutsche Institut für Normung, a German standardization body. Rails are generally available in aluminum or steel and may be cut for installation. Depending on the requirements of the mounted components, the rail may need to be grounded. collapse


    Black Box Explains…Media converters that also work as switches.

    Media converters transparently convert the incoming electrical signal from one cable type and then transmit it over another type—thick coax to Thin, UTP to fiber, and so on. Traditionally, media... more/see it nowconverters were purely Layer 1 devices that only converted electrical signals and physical media and didn’t do anything to the data coming through the link.

    Today’s media converters, however, are often more advanced Layer 2 Ethernet devices that, like traditional media converters, provide Layer 1 electrical and physical conversion. But, unlike traditional media converters, they also provide Layer 2 services and route Ethernet packets based on MAC address. These media converters are often called media converter switches, switching media converters, or Layer 2 media converters. They enable you to have multiple connections rather than just one simple in-and-out connection. And because they’re switches, they increase network efficiency.

    Media converters are often used to connect newer 100-Mbps, Gigabit Ethernet, or ATM equipment to existing networks, which are generally 10BASE-T, 100BASE-T, or a mixture of both. They can also be used in pairs to insert a fiber segment into copper networks to increase cabling distances and enhance immunity to electromagnetic interference.

    Rent an apartment…
    Media converters are available in standalone models that convert between two different media types and in chassis-based models that house many media converters in a a single chassis.

    Standalone models convert between two media. But, like a small apartment, they can be outgrown.

    Consider your current and future applications before selecting a media converter. A good way to anticipate future network requirements is to choose media converters that work as standalone devices but can be rackmounted if needed later.

    …or buy a house.
    Chassis-based or modular media converter systems are normally rackmountable and have slots to house media converter modules. Like a well-planned house, the chassis gives you room to grow. These are used when many Ethernet segments of different media types need to be connected in a central location. Modules are available for the same conversions performed by the standalone converters, and they enable you to mix different media types such as 10BASE-T, 100BASE-TX, 100BASE-FX, ATM, and Gigabit modules. Although enterprise-level chassis-based systems generally have modules that can only be used in a chassis, many midrange systems feature modules that can be used individually or in a chassis. collapse

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