Cables

The news on bandwidth
The need for increased bandwidth never ceases—the more you have, the more you need. Applications keep getting more complex, and files keep getting bulkier. It won’t be long before you need to increase the speed of your network.

Don’t worry. Black Box experts are ready 24 hours a day to answer your questions. When you click on “Talk to a Tech,” you’ll be talking to a trained expert in seconds. If you need help installing a network, or adding an additional drop, contact us.

Because unshielded twisted-pair UTP cable is by far the most common networking cable, let’s take a brief look at where UTP is headed.

The limits of Category 5
Category 5 (CAT5) cabling is good, solid cable for 100-Mbps LANs. The Category 5 standard has been around since 1991, so it’s well established. You’ll find existing Category 5 installations everywhere. What can Category 5 cable do, and what can’t it do?

If you still have a lot of 10-Mbps equipment, CAT5 cabling will serve your needs. It also handles 100-Mbps Fast Ethernet transmissions very well.

But if you’re running up against the performance limits of a 100-Mbps network, you’ll probably want to upgrade at least parts of your system fairly soon to Category 5e (CAT5e) or higher.

Category 5e: the improved Category 5
Category 5e, also known as Enhanced Category 5, or CAT5e, was ratified in 1999. It’s an incremental improvement designed to enable cabling to support full-duplex Fast Ethernet operation and Gigabit Ethernet.

The main differences between CAT5 and CAT5e can be found in the specifications. The performance requirements have been raised slightly in the new standard.

CAT5e has stricter specifications for Power Sum Equal-Level Far-End Crosstalk (PS-ELFEXT), Near-End Crosstalk (NEXT), Attenuation, and Return Loss (RL) than those for CAT5. Like CAT5, CAT5e is a 100-MHz standard, but it has the capacity to handle bandwidth superior to that of CAT5. With these improvements, you can expect problem-free, full-duplex, 4-pair Ethernet transmissions over your CAT5e UTP.

Category 6
The next level in the cabling hierarchy is Category 6 (CAT6) (ANSI/TIA/EIA-568-B.2-1), which was ratified by the TIA/EIA in June 2002. CAT6 provides higher performance than CAT5e and features more stringent specifications for crosstalk and system noise.

The quality of the data transmission depends upon the performance of all the components of the channel. So to transmit according to CAT6 specs, the jacks, patch cables, patch panels, cross-connects, and cabling must all meet CAT6 standards. (The channel includes everything from the wallplate to the wiring closet.) The CAT6 components are tested individually, and they are also tested together for performance. In addition, the standard calls for generic system performance so that CAT6 components from any vendor can be used in the channel.

CAT6 channel transmission requirements should result in a Power-Sum Attenuation-to-Crosstalk Ratio (PS-ACR) that’s greater than or equal to zero at 200 MHz.

In addition, all CAT6 components must be backward compatible with CAT5e, CAT5, and CAT3. If different category components are used with CAT6 components, then the channel will achieve the transmission performance of the lower category. For instance, if CAT6 cable is used with CAT5e jacks, the channel will perform at a CAT5e level.

Industry standards
The advantage of sticking to the industry standards is the knowledge that your cabling will be compatible with standards applications. But the standards are always being improved upon, and it takes time to ratify a new standard. Often, as with CAT6, the final standard may be different from the proposed standard. For the latest information, contact our FREE Tech Support.

Twisted-Pair Cable Specifications Comparison
Frequency — CAT5, CAT5e: 100 MHz;
CAT6: 250 MHz;
CAT7 (Proposed): 600 MHz
Attenuation (min. at 100 MHz) — CAT5, CAT5e: 22 dB;
CAT6: 19.8 dB;
CAT7 (Proposed): 20.8 dB
Characteristic Impedance — All: 100 ohms ± 15%
NEXT (min. at 100 MHz) — CAT5: 32.3 dB;
CAT5e: 35.3 dB;
CAT6: 44.3 dB;
CAT7 (Proposed): 62.1 dB
PS-NEXT (min. at 100 MHz) — CAT5: no specification;
CAT5e: 32.3 dB;
CAT6: 42.3 dB;
CAT7 (Proposed): 59.1 dB
ELFEXT (min. at 100 MHz) — CAT5: no specification;
CAT5e: 23.8 dB;
CAT6: 27.8 dB;
CAT7 (Proposed): not yet specified
PS-ELFEXT (min. at 100 MHz) — CAT5: no specification;
CAT5e: 20.8 dB;
CAT6: 24.8 dB;
CAT7 (Proposed): not yet specified
Return Loss (min. at 100 MHz) — CAT5: 16 dB;
CAT5e: 20.1 dB;
CAT6: 20.1 dB;
CAT7 (Proposed): 14.1 dB
Delay Skew (max. per 100 m) — CAT5: no specification;
CAT5e: 45 ns:
CAT6: 45 ns;
CAT7 (Proposed): 20 ns

The original Token Ring specifications called for shielded twisted-pair (STP) cable using either a DB9 connector or a unique square connector called the IBM data connector. Later, Token Ring was adapted to use conventional unshielded twisted-pair (UTP) cable with RJ-45 connectors. The most common kinds of Token Ring cabling in use to day are Type 1 and Type 6 STP as well as Type 3 UTP.

Type 1 shielded twisted-pair (STP) cable is the original wiring for Token Ring. In Type 1 cabling, each wire is constructed of 22 AWG solid copper. Type 1 cable is not as flexible as Type 6 cable and is generally used for long runs in areas where twists and turns are less likely, such as in walls or conduits.

Type 6 Token Ring cable is a lighter, more pliable version of Type 1 cable. It’s constructed of two stranded 26 AWG copper pairs that are surrounded by an overall braided shield. Type 6 cable is commonly used in offices and open areas, and its flexible construction enables it to negotiate multiple twists and turns.

Type 3 or UTP Token Ring cabling uses the same twisted-pair CAT3, CAT5, or CAT5e cabling with RJ-45 connectors as 10BASE-T Ethernet does. Attaching older Type 1 Token Ring to UTP Token Ring requires a balun or adapter.

Category 6 has more stringent specifications for crosstalk and system noise than CAT5e. For cabling to transmit according to CAT6 specs, it must be used in a complete channel solution with vendor-specific jacks, patch cords, and patch panels, and the cabling must be tuned correctly. GigaTrue™ is the channel solution offered by Black Box.

The minimum GigaTrue NEXT (Near-End Crosstalk) specification at 100 MHz is 41.8 dB, allowing for 1.9 dB of headroom above the CAT6 channel specification. In theory, a channel with headroom like this performs better than a channel that only meets the minimum requirements.

You can always contact Black Box Tech Support to answer your cabling questions. Our techs can recommend cable testers and steer you in the right direction when you’re installing new cabling. And the advice is FREE!

The environment determines whether cable should be shielded or unshielded.

Shielding is the sheath surrounding and protecting the cable wires from electromagnetic leakage and interference. Sources of this electromagnetic activity (EMI)—commonly referred to as noise—include elevator motors, fluorescent lights, generators, air conditioners, and photocopiers. To protect data in areas with high EMI, choose a shielded cable.

Foil is the most basic cable shield, but a copper-braid shield provides more protection. Shielding also protects cables from rodent damage. Use a foil-shielded cable in busy office or retail environments. For industrial environments, you might want to choose a copper-braid shield.

For quiet office environments, choose unshielded cable.

V.35 is the ITU (formerly CCITT) standard termed “Data Transmission at 48 kbps Using 60–108 KHz Group-Band Circuits.“

Basically, V.35 is a high-speed serial interface designed to support both higher data rates and connectivity between DTEs (data-terminal equipment) or DCEs (data-communication equipment) over digital lines.

Recognizable by its blocky, 34-pin connector, V.35 combines the bandwidth of several telephone circuits to provide the high-speed interface between a DTE or DCE and a CSU/DSU (Channel Service Unit/Data Service Unit).

Although it’s commonly used to support speeds ranging anywhere from 48 to 64 kbps, much higher rates are possible. For instance, maximum V.35 cable distances can theoretically range up to 4000 feet (1200 m) at speeds up to 100 kbps. Actual distances will depend on your equipment and cable.

To achieve such high speeds and great distances, V.35 combines both balanced and unbalanced voltage signals on the same interface.

CAT6a is a 10-Gigabit Ethernet (10-GbE) over copper standard. Its requirements are covered in ANSI/TIA-568-C.2 (Balanced Twisted-Pair Telecommunications Cabling and Components Standard) published in August 2009. The standard defines 10-Gigabit data transmission over a 4-connector twisted-pair copper cable for a distance of 100 meters on CAT6a copper cabling. This ensures that the system is ready to support IEEE 802.3an, the IEEE standard for 10GBASE-T, which specifies using Class E-augmented cable.

CAT6a extends electrical specifications from 250 MHz to 500 MHz. It also features Power-Sum Alien Crosstalk (PS-ANEXT) to 500 MHz. Alien Crosstalk (ANEXT) is a coupled signal in a disturbed pair arising from a signal in a neighboring cable. To virtually eliminate the problem of ANEXT, CAT6a F/UTP cable is used. The F indicates an outer foil shield that eliminates PS-ANEXT. When security is an issue, CAT6a is a good choice because it doesn’t emit signals. In addition, CAT6a F/UTP cable works well in noisy environments with a lot of EMI.

What is Fibre Channel?
Fibre Channel is a set of communication standards designed to provide high-speed data transfer over a duplex, serial interface. It’s an open standard that supports multiple protocols including higher-level protocols, such as FDDI, SCSI, HIPPI, and IPI, to manage data transfer.

Although it operates at a range of 133 Mbps to 4 Gbps, Fibre Channel is most commonly used at speeds of 1 or 2 Gbps. A working standards group recently announced that 10-Gbps speeds are expected in soon.

Why is it called Fibre Channel?
Originally, Fibre Channel was designed to support only fiber. When copper was added, the International Standards Organization (ISO) task force changed the spelling of fiber to fibre instead of renaming the technology.

Fibre Channel history.
Fibre Channel was first developed in 1988, and the American National Standards Institute (ANSI) formed a committee in 1989. To ensure interoperability, IBM®, Hewlett-Packard®, and Sun Microsystems® formed the FCSI (Fibre Channel Systems Initiative), a temporary organization, in 1992. FCSI later dissolved, and development was handed over to the FCA (Fibre Channel Association) in 1994. ANSI accepted Fibre Channel as a standard in 1994.

The best of both worlds.
This hardware-based standard combines the best of both channel and network communication methods into one I/O interface. It takes advantage of hardware-intensive, quicker point-to-point channel links that offer low overhead, such as SCSI bus technology, as well as the broad connectivity and long-distance benefits of software-intensive network technology.

Where Fibre Channel is used.
Fibre Channel is used to transfer large amounts of data quickly between supercomputers, mainframes, workstations, desktop computers, storage devices, displays, and other peripherals.

Fibre Channel offers reliability, scalability, congestion-free data flow, Gigabit bandwidth, compatibility with multiple topologies and protocols, flow control, self management, hot pluggability, speed, cost efficiency, loop resiliency, and distance. This makes it ideal for large data operations such as Internet/intranets, data warehousing, networked storage, integrated audio/video, real-time computing, on-line services, and imaging.

The most popular application for this technology right now is Storage Area Networks (SANs). Independent methods of centralized storage management within a SAN (e.g., RAID, tape backup or library, CD-ROM library) run more efficiently with a Fibre Channel backbone.

Fibre Channel topologies.
Fibre Channel can be connected by three methods. In all cases, the topology of the network is transparent to the attached devices.

Point to point is the simplest topology, which uses simple bidirectional links between two connected devices.

Arbitrated loop is the most common topology and the most complex. It is distributed, connecting up to 126 devices across shared media, and it offers shared bandwidth. Two ports on the loop establish a point-to-point, full-duplex connection through arbitration among all ports.

The cross-point or fabric-switched topology uses 24-bit addressing to connect up to 2 (to the 24th) devices in a cross-point switched configuration. This enables many devices to communicate at the same time and does not require shared media.

Fibre Channel layers.
Fibre Channel protocol is divided into five hierarchical layers: The three bottom layers, FC-0–FC-2, define the physical transmission standard. Layers FC-3 and FC-4 address interfaces with other network protocols.

FC-0: Media and interface layer that defines the physical link.

FC-1: Transmission encode/decode layer. Information is encoded 8 bits at a time into a 10-bit transmission character (8B/10B from IBM).

FC-2: Signaling protocol layer that serves as the transport mechanism performing basic signaling and framing. FC-2 includes the following classes of service:
• Class 1 provides dedicated connections. Intermix is an optional type of Class 1 service in which Class 1 frames are guaranteed a special amount of bandwidth.
• Class 2 is a frame-switched, connectionless service, also known as multiplex. It guarantees delivery and confirms receipt of traffic.
• Class 3 is a one-to-many, connectionless, frame-switched service. It’s similar to Class 2 except it uses buffer-to-buffer flow control and does not confirm frame delivery.

FC-3: Common-services layer that provides common services required for advanced features such as striping, hunt groups, and multicast.

FC-4: Upper layer for protocol mapping of network and channel data transmitting concurrently over the same physical interface.

Fibre Channel media.
Fibre Channel runs at up to 1 Gbps over copper or fiber, but for higher speeds, fiber is required. Copper-wire cable can be video coax, miniature coax, or, most commonly, shielded twisted pair with a DB9 or HSSDC connector. Fiber choices include 62.5- or 50-µm multimode and 7- or 9-µm single-mode fiber, all with an SC connector.

Other Fibre Channel equipment includes disk enclosures, drivers, extenders, hubs, interface converters, host bus adapters, routers, switches, and SCSI bridges.