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Frequently Asked Questions
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The Questions:
- What is a network?
- What makes a network work?
- Is Fast Ethernet the best type of network?
- What kind of cable do I need for a network?
- What is the difference between "Serial" and "Parallel"?
- What is the flammability rating for PLENUM?
- What is the flammability rating for RISER?
- What is the flammability rating for GENERAL PURPOSE?
- What is the flammability rating for RESIDENTIAL?
- What is the MT-RJ connector and how does it work?
- What does OFNR fiber cable designation mean?
- What does OFNP fiber cable designation mean?
- What is S-Video?
- What is the difference between a "coupler" and an "adapter"?
- What is LVD?
- What is LVD/SE?
- What is SE?
- What is HVD?
- What is U2W?
- What is Ultra160/m?
- What is a firewall?
- What is a Fire Stop?
- What is the difference between CAT5, CAT5-E, CAT6 and CAT7?
- What is CAT6 cable?
- What is the difference between Solid and Stranded conductors?
- What is the difference between UTP and STP cable?
- When should Shielded (STP) cable be used?
- When do you use Plenum Cable?
- What is USB?
- How does USB work?
- What is the maximum distance for USB?
- What makes a good KVM Switch?
The Answers:
- What is a network?
A network is a system that connects two or more computers and peripherals (such as a printer, CD-ROM drive, scanner, etc.), so that the computers can communicate with each other directly, and peripherals can be used by more than one computer.
- What makes a network work?
An Ethernet Local Area Network (LAN) is made up of both Hardware and Software. Network Interface Cards (NICs) transmit and receive the data over the LAN to and from a PC. A Hub connects all the PCs together on the LAN. The PCs and Hub are connected together with unshielded CAT5E or CAT6 cable.
- Is Fast Ethernet the best type of network?
Fast Ethernet is by far the most popular technology standard for connecting computers into a local area network (LAN). It is fast, reliable, and stable, and is currently in more than 100 million computer connections around the world. Fast Ethernet runs at 100Mbps, which is 10 times that of regular Ethernet.
- What kind of cable do I need for a network?
UTP is recommended because it is easy to set up and expand your network simply by "plugging-in" new PCs or other Ethernet devices. CAT5 supports speeds of up to 100Mpbs using Fast Ethernet.
- What is the difference between "Serial" and "Parallel"?
Generally speaking, Serial and Parallel are two different communications modes. Serial data is transmitted in single bits, one by one. Parallel data is transmitted in multiple bits and at the same time. Most printers are parallel printers and print much faster than serial printers. Most computers come with both a serial port (usually a DB9 Male and/or DB25 Male) and a parallel port (usually a DB25 Female). Serial ports are sometimes labeled COM1, COM2, etc. and parallel ports are sometimes labeled LPT1, LPT2, etc. A serial port and a parallel port cannot communicate with each other. To connect two computers via serial ports would require a serial null-modem cable. To connect two computers via parallel ports (printer ports) would require a parallel data transfer cable with DB25 Male connectors.
- What is the flammability rating for PLENUM?
- Highest flame resistance
- Suitable for use in areas designed as plenums
- NEC Communications Cable Code: CMP
- UL-910 Steiner tunnel flame test
- What is the flammability rating for RISER?
- Suitable for vertical installation between building floors
- NEC Communications Cable Code: CMR
- UL-1666 Vertical shaft flame test
- What is the flammability rating for GENERAL PURPOSE?
- Used in broad applications
- NEC Communications Cable Code: CMG
- UL-1581 Vertical tray flame test
- What is the flammability rating for RESIDENTIAL?
- Lowest flame resistance
- NEC Communications Cable Code: CMX
- UL-1581 VW-1 Vertical flame test
- What is the MT-RJ connector and how does it work?
The MT-RJ is one of the newly emerging Small Form Factor connectors that are becoming commonplace in the networking industry. The MT-RJ utilizes two fibers and integrates them into a single design that looks similar to a black RJ45 modular connector. Alignment is completed through the use of two pins that mate with the connector. Transceiver jacks found on NICs and equipment typically have the pins built into them. Users need to be careful that one connector has alignment pins when mating two MT-RJ cables through a coupler.
- What does OFNR fiber cable designation mean?
OFNR (Optical Fiber Nonconductive Riser) - This is a cable containing only glass fiber with no copper conductive elements. It is generally intended for vertical runs between floors as part of a fiber backbone. This type of cable complies with the Underwriters Laboratories (UL) fire safety test Riser/1666.
- What does OFNP fiber cable designation mean?
OFNP (Optical Fiber Nonconductive Plenum) - This is a cable containing only glass fiber with no copper conductive elements. It is generally intended for horizontal runs, especially within an air handling conduit. This type of cable complies with the Underwriters Laboratories (UL) fire safety test Plenum/910.
- What is S-Video?
The term "S-Video" is derived from the way the video signal is transmitted. In S-Video, the signal is separated into two components, hence the term "Separate Video" or "S-Video". Two 75 Ohm coaxial cables and a MiniDIN 4 connector are utilized to transmit the two component signals. One of the coaxial cables carries the Luminance Signal (brightness or Y component), while the second 75 Ohm coaxial cable carries the Chrominance Signal (color or C component). By separating the video signal into two components, a better quality picture is produced than composite video that utilizes one coaxial cable to transmit both signals.
- What is the difference between a "coupler" and an "adapter"?
Couplers and adapters are used to join together individual connectorized cables. If the two cables to be connected have the SAME style connectors, then the connecting device is called a "coupler." If the two cables to be connected have DIFFERENT style connectors, then the connecting device is called an adapter.
- What is LVD?
LVD stands for Low Voltage Differential, which is one of three categories of SCSI signaling/termination. LVD is the newest/latest type of signaling because it offers extended length and greater legacy support (if LVD/SE). You can go 12 meters (which is roughly 40 ft.) Many new hard drives are LVD now days.
- What is LVD/SE?
LVD/SE stands for "Multimode Low Voltage Differential and Single Ended". Most LVD devices support LVD/SE. the term multimode is very tricky, however, because it makes you think that devices can run in LVD and SE mode at the same time. This is NOT the case - a LVD/SE drive must run in LVD or SE mode.
- What is SE?
SE stands for Single Ended, which is one of three categories of SCSI signaling/termination. Single Ended is the most common form of SCSI signaling. Most devices today use SE: Zip, Jazz, scanners, and almost all 50-pin SCSI devices fit into this category. Ultra Wide hard drives are commonly SE also. SE typically needs to be (1.5 meters) 5 feet or less of total bus length.
- What is HVD?
HVD stands for High Voltage Differential, or just "Differential", and is one of three categories of SCSI signaling/termination. HVD is great for applications where you have devices a long ways apart from each other, or if you are in a high noise environment. You can go 25 meters on a differential bus. This is the signaling that allows you the longest runs.
- What is U2W?
U2W is "Ulta2 Wide", which is marketing term for "16 bit Fast-40" or "80 MB/Sec." It refers to the speed at which your SCSI bus is running. Only LVD and HVD can run in Ultra2 Wide mode.
- What is Ultra160/m?
Ultra 160/m is an implementaion of Ultra3 Wide featured by Seagate and Adaptec, and other vendors. It runs with a bus bandwidth of 160 MB/Sec. Ultra 160/m uses LVD signaling. Ultra2 Wide and Ultra 160/m devices can co-exist on an LVD bus with no speed penalties. To get your drives running in Ultra 160 mode, your terminator must be Ultra 160 compatible.
- What is a firewall?
Firewalls are software-/hardware-based security components that divide computer networks into logical segments: an unsecured side that remains exposed to computer users from the outside world, typically to provide access to Web servers or other such "public" parts of a nework; and a second, secure side that's off-limits to intruders, yet remains accessible to users. There are three types of firewalls: (1) Packet filters are hardware firewalls (implemented in bridges or routers) that examine the source or destination address of a data packet to determine whether or not it should be forwarded to the next segment of a network; (2) Application servers are software firewalls that exist only to support particular applications (such as email or a Web server) and grant access to such services according to guideliines set by the system manager who configures the application; and (3) Software-based circuit-level gateways fall somewhere between the other two types of firewalls. They don't actually host network services like application servers do; rather, they grant access to such services based on the unique identity of the network port through which the request for service is received - like a packet filter routing data based on addresses.
- What is a Fire Stop?
During new cable installations, cable is often routed through walls, floors, and ceilings. The cable routing holes leave an exposed air gap in the walls. To accommodate the cable, the routing holes are obviously larger than the cable. These routing holes can be a fire hazard. The air gap between the cable and wall provides an easy way for fire to spread from one room to another. Fire-Stop Putty is intumescent, which means that when it's exposed to heat, the putty expands around the cable to seal the opening and prevent the spread of fire and gas from one side of the wall to the other. Fire-Stop Putty also works as an insect barrier by sealing open spaces and access routes into rooms and buildings.
- What is the difference between CAT5, CAT5-E, CAT6 and CAT7?
The simple answer is: CAT5 is rated to 100M; CAT5E is rated to 350M; CAT6 and CAT6e is rated to 550M or 1000M, depending on your source; CAT7 is supposedly rated to 700M or presumably 1000M. CAT5e, aka Enhanced Category 5, was ratified in 1999, designed to enable cabling to support full-duplex Fast Ethernet operation and Gigabit Ethernet. 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. CAT5E is completely backward compatible with current CAT5 equipment. CAT6 cable is being made with 23 guage wire as opposed to the slightly smaller 24 guage for CAT5E, and also has a separator to handle crosstalk better.
- What is CAT6 cable?
Category 6 (CAT6) was ratified in June 2002. To transmit according to CAT6 specifications, every component from the wiring closet to the wallplate, ie, the cable, keystone jacks, patch cables, patch panels, cross-connects must ALL meet CAT6 standards. CAT6 channel transmission requirements should result in a Power-Sum Attenuation-to-Crosstalk Ratio (PS-ACR) that is greater than or equal to zero at 200MHz. In addition, all CAT6 components must be backward compatible with CAT5e, CAT5 and CAT3. If CAT6 cable is used with CAT5e jacks, the channel will achieve the transmission performance of the lower category, that is, at the CAT5e level.
- What is the difference between Solid and Stranded conductors?
SOLID cable is designed for both horizontal and backbone cable runs. It is used for runs betwen two wiring closets, or from the wiring closet to a wallplate. Solid-conductor cable shouldn't be bent, flexed, or twisted repeatedly. STRANDED cable is much more flexible than solid-core cable. It is designed for use in shorter runs, such as between the NIC (Network Interface Card) in your computer to the wallplate, or between concentrators and patch panels, hubs or switches.
- What is the difference between UTP and STP cable?
UTP - Unshielded Twisted Pair - is used in environments where EMI (commonly referred to as "noise") is not a problem.
STP - Shielded Twisted Pair - is used in environments with high levels of EMI, such as industrial environments.
- When should Shielded (STP) cable be used?
The environment in which the cable will be installed determines whether you should use Shielded Twisted Pair (STP) or Unshielded Twisted Pair (UTP). Shielding is the sheath surrounding and protecting the cable wires from electromagnetic interference (EMI) - commonly referred to as "noise". Sources of EMI include:
- fluorescent lights
- air conditoners
- photocopiers
- elevator motors
- generators
Use Shielded cable to protect your data in areas with high levels of EMI.
- When do you use Plenum Cable?
In building construction, the space used for air circulation (heating and air conditioning) is called "the plenum." This space is also commonly used to route communications cable. This poses a serious hazard in the event of fire due to lack of barriers to contain the smoke and flames. This is why various fire codes and the National Electric Code (NEC) require the use of fire resistant and low smoke producing cable in these plenum areras. This type of cable is called "plenum cable" which is made with a fire retardant compound that exhibits self-extinguishing characteristics.
- What is USB?
USB (Universal Serial Bus) is a technology that allows computer users to connect up to 127 devices to their computer at the same time, ie, USB scanners, USB keyboards, USB mice, USB digital cameras, USB-to-ethernet adapters, USB telephones, USB digital joysticks, USB CD-ROM drives, USB, hubs, USB tape drives, USB floppy drives, etc.
- How does USB work?
USB connectivity is a host-client system. Your computer controls your USB devices through a tree-like directory. USB cables always have the A-connector facing toward the host (your computer) and the B-connector facing toward the clients (USB devices). USB hubs will lie in between your computer and your devices with the Type-B port on the upstream side, and the Type-A ports on the downstream side.
- What is the maximum distance for USB?
The maximum distance between most USB devices and your computer is generally 5 meters (16 feet). Slow USB devices such as mice and keyboards have a maximum distance of only 3 meters (9.5 feet). One way to extend this distance is to use USB hubs (which repeat a signal). You can go an additional 5 meters if you put a hub between your computer and your USB device(s). You can do this up to 5 times for a maximum distance of 30 meters (98.5 feet).
- What makes a good KVM Switch?
When choosing a KVM switch, there are several features to look for. Electronic KVM Switches use microprocessors. OSD (On Screen Display): OSD provides easy-to-read, pop-up menus for identifying and selecting computers via hot keys. You can also name computers to make it easier to connect to the right one. Hot Key Switching: Hot key switching allows you to switch between computers without pushing the buttons on the actual switch. It can be a combination of keys or hitting a button a couple of times. Port Emulation: Keyboard and Mouse port emulation makes sure that the computer still things the keyboard and mouse are connected directly to the computer. This allows you to boot all compuers connected to the switch at the same time. High Resolution Video: A good KVM will support monitor resolutions up to 2048x1536 with no signal degradation. Peripheeral compatibility: With the wide variet of keyboards, monitors and mice available, compatibility issues can result in lockups that disrupt operations. The KVM switch should be designed to eumulate all variations of the different devices, including specialized devices such as the Microsoft Intellimouse.
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