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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


Black Box Explains...RS-232.

RS-232, also known as RS-232C and TIA/EIA-232-E, is a group of electrical, functional, and mechanical specifications for serial interfaces between computers, terminals, and peripherals. The RS-232 standard was developed by... more/see it nowthe Electrical Industries Association (EIA), and defines requirements for connecting data communications equipment (DCE)—modems, converters, etc.—and data terminal equipment (DTE)—computers, controllers, etc.) devices. RS-232 transmits data at speeds up to 115 Kbps and over distances up to 50 feet (15.2 m).

The standard, which is functionally equivalent to ITU V.24/V.28, specifies the workings of the interface, circuitry, and connector pinning. Both sync and async binary data transmission fall under RS-232. Although RS-232 is sometimes still used to transmit data from PCs to peripheral devices, the most common uses today are for network console ports and for industrial devices.

Even though RS-232 is a “standard,” you can’t necessarily expect seamless communication between two RS-232 devices. Why? Because different devices have different circuitry or pinning, and different wires may be designated to perform different functions.

The typical RS-232 connector is DB25, but some PCs and other data communication devices have DB9 connectors and many newer devices have RJ-45 RS-232 ports. To connect 9-pin PC ports or RJ-45 to devices with 25-pin connectors, you will require a simple adapter cable. collapse


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... SNMP.

SNMP (Simple Network Management Protocol) management is the standard for LAN management, particularly in mission-critical applications. The standard is controlled by the Internet Engineering Task Force (IETF). It was designed... more/see it nowto manage network configuration, performance, faults, accounting, and security.

An SNMP agent must be present at the device level (a router or a hub, for example), either built into the unit or as a proxy agent, and is accessed through a remote terminal. SNMP does not follow a polling protocol. It waits to receive data from the remote device or sends data based on operator commands.

By using one common set of standards, SNMP enables network administrators to manage, monitor, and control their SNMP-compliant network equipment with one management system and from one management station. If a network device goes down, it|s possible to both pinpoint and troubleshoot the problem more efficiently. And a network administrator isn’t limited to equipment from just one vendor when using an SNMP program. collapse


Black Box Explains... How Autocross conversion can work for you.

When using media converters with 10BASE-T or 100BASE-TX cable, you may need to connect your converter to a non-hub device such as a PC or printer.

According to IEEE 802.3 Ethernet... more/see it nowstandards, media converters originally needed a specially pinned crossover cable to connect to PCs. The crossover cable matches the devices’ transmit and receive pins. Now there are media converters that use straight-pinned 10BASE-T patch cable but incorporate an uplink or crossover connection—a switch on the converter that’s set to support the PC-to-converter connection. By setting the uplink switch to “cross,” the converter’s internal mechanism crosses the pins on the RJ-45 connector to simulate a crossover cable.

Autocross conversion eliminates both the need to crosspin cables and set an uplink switch. It adapts to the pin assignment of the twisted-pair cable whether it’s crossed or uncrossed. And because it senses the pin configuration of any cable pinned to Ethernet specifications, it adjusts automatically without user configuration. collapse

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