07+Transmission+Media

07 Transmission Media - [[file:ch_07.ppt]]
Any thing that can carries information from a sources to a destination. The transmission media is usually Free Space, Metallic cables, Fiber-Optic cables.They are of two types: Guided and Unguided media. -- source: http://www.computer-network.net/lan-cable  = Cabling = 
 * Transmission media lie below the physical layer.
 * A guided medium provides a physical conduit from one device to another.
 * Twisted-pair cable, coaxial cable, and optical fiber are the most popular types of guided media.
 * Twisted-pair cable consists of two insulated copper wires twisted together. Twisting allows each wire to have approximately the same noise environment.
 * Twisted-pair cable is used in telephone lines for voice and data communications.
 * Coaxial cable has the following layers (starting from the center): a metallic rod-shaped inner conductor, an insulator covering the rod, a metallic outer conductor (shield), an insulator covering the shield, and a plastic cover.
 * Coaxial cable can carry signals of higher frequency ranges than twisted-pair cable.
 * Coaxial cable is used in cable TV networks and traditional Ethernet LANs.
 * Fiber-optic cables are composed of a glass or plastic inner core surrounded by cladding, all encased in an outside jacket.
 * Fiber-optic cables carry data signals in the form of light. The signal is propagated along the inner core by reflection.
 * Fiber-optic transmission is becoming increasingly popular due to its noise resistance, low attenuation, and high-bandwith capabilities.
 * Signal propagation in optical fibers can be multimode (multiple beams from a light source) or single-mode (essentially one beam from a light source).
 * In multimode step-index propagation, the core density is constant and the light beam changes direction suddenly at the interface between the core and the cladding.
 * In multimode graded-index propagation, the core density decreases with distance from the center. This causes a curving of the light beams.
 * Fiber-optic cable is used in backbone networks, cable TV networks, and Fast Ethernet networks.
 * Unguided media (usually air) transport electromagnetic waves without the use of a physical conductor.
 * Wireless data is transmitted through ground propagation, sky propagation, and line-of-sight propagation.
 * Wireless data can be classifed as radio waves, microwaves, or infrared waves.
 * Radio waves are omnidirectional. The radio wave band is under government regulation.
 * Microwaves are unidirectional; propagation is line of sight. Microwaves are used for cellular phone, satellite, and wireless LAN communications.
 * The parabolic dish antenna and the horn antenna are used for transmission and reception of microwaves.
 * Infrared waves are used for short-range communications such as those between a PC and a peripheral device.

What is LAN Cable?
Even though today the wireless era is so popular, the need of **LAN Cabling** is still in demand particularly for large scale network with mix wired and wireless networks. Network cable takes very important role in the overall performance of large networks. Therefore, understanding the bottom line of well managed network cable is very essential before you develop a large networking infrastructure. Implementation of high speed LAN network to support applications and services today and in the future is necessary to provide scalable bandwidth necessary. Traditionally UTP structured cabling system is used to provide high speed and reliable connectivity using popular technologies fast Ethernet (100Mbps) or Gigabit Ethernet technology. Gigabit Ethernet for backbone //LAN cabling// is recommended today for the future expansion of cable networks. As for the high speed transmission between the LAN, backbone of the fiber optics needed to Gigabit Ethernet (GE) or even faster speeds 10GE/100GE.

Minimum Requirements of Computer network
A well designed of **LAN cabling** is required for reliable and high performance wired connectivity. The following list the minimum requirements and standard recommendation for computer networking system:
 * 1) Certified Cat5e (Enhanced) UTP cable must be used for all structured cabling. This Cat5e can support the gigabit speed
 * 2) All UTP cable segments must be less than 100 meters (around 300 ft) for all patch leads, wall and roof cabling in total and must be Cat5e compliant.
 * 3) All types of Cat5 must be replaced with new certified Cat5e cabling.
 * 4) Documentation for all the computer network cabling must be done. All the patches must be managed in a tidy fashion to a secure location. Labeling must also be provided for all patch panel and wall points

Recommended requirements
Additional requirements as above plus the following list for recommended requirements for best performance of your LAN cabling infrastructure.
 * 1) Fiber optic cable must be used for backbone links that require gigabit and even higher speed. For segments less than 400 meters, the MMF (Multi-mode fiber) connection which is less expensive should be used. For segments up to 2 Km long, the SSF (single-mode fiber) should be used. SC or MT-RJ type interfaces must be used for new fiber optic connectors.
 * 2) Standard Color coded and proper labeling should be used. All cabling system including wall points and patch panels must be properly labeled and color coded.
 * 3) To ensure that all cabling is correctly patched and is tidy, an ongoing cable management process must be in place.

Types of LAN Cabling
The need for network cabling within your network infrastructure can be categorized into several types of cable as follows.

Coaxial Cables
The first generation of network cable is coaxial which was used for 10Base2 and 10Base5 Ethernet in the past years. 10Base5 used thicker coaxial cable than 10Base2 did. They are regarded as legacy technology today, no longer used in the recent years due to Fast Ethernet Era. Figure 1 shows a section diagram of coaxial cable that includes the outer jacket; braided copper shielding; plastic insulation; copper conductor and BNC connector. Fig. 1 – Lan Cable – coaxial section diagram Ethernet network technology originally was based on coaxial cabling which could extend up to 500 meters per segment with the maximum speed up to 10Mbps. It was very difficult when you should troubleshooting network disconnection problem.

UTP and STP
There are two types of copper-wire UTP (Unshielded Twisted Pair) and STP (Shielded twisted pair) cables but the most popular is the UTP cables.

Fig 2 Lan Cable – UTP and STP cable section diagram The figure 2 shows most of the pertinent details of both types of UTP and STP cables diagram. UTP cable contains 4 pairs of color coded plastic insulation. The grade of the cable can be identified by the following factors: The maximum length of the cable can be extended should not exceed 300 ft (100 meters). You cannot guarantee the length more than 300 ft. because the signal strength attenuation becomes more significant. Cat5e UTP cable can deliver speeds of up to 1Gigabit identified by the number of twists per inch which is slightly higher with single nylon jacket insulation.
 * 1) The number of twists per inch
 * 2) The less attenuation
 * 3) Less signal interference
 * 4) Less crosstalk

UTP standard
There are many Cat 6 UTP plenum-rated cables available in the market today for example from //Cable to Go// 43092 Cat6 550MHz. Check here for cable and other networking store.
 * 1) Category 1, for telephones but not for data.
 * 2) Category 2, maximum speed is 4 Mbps, originally intended to support Token Ring over UTP.
 * 3) Category 3, maximum speed is 10 Mbps. It can be used for telephones as well, option for Ethernet in years past.
 * 4) Category 4, maximum speed is 16 Mbps, for the fast Token Ring.
 * 5) Category 5, maximum speed is 1Gbps, very popular for Computer network cable.
 * 6) Category 5e, maximum speed is 1Gbps, lower emission, more expensive than Cat5, but better for Gigabit Ethernet.
 * 7) Category 6, maximum speed is 1Gbps+, intended as a replacement for Cat5e with capabilities to support multigigabit speeds.

UTP Best practice
Do not upgrade CAT5 cabling unnecessarily to CAT5e. CAT5e is the current LAN cabling standard that defines connectivity at 10/100 Mbps and provides support for future gigabit to the desktop speeds. Both CAT3 and CAT5 have been superseded by CAT5e, and are no longer recognized as current cabling standards. Existing CAT5 will however support 10/100 Mbps data speeds, but not 1000 Mbps services Gigabit over certified UTP is possible by using CAT5e structured cabling. Certified UTP cabling is best deployed for all horizontal wiring including both data and phone connections. Ensuring a minimum of two connections at the desktop will allow for both data and current voice connections. Termination of the cabling at the Main Distribution Frame (MDF) should allow for segmentation of the voice and data cabling.

UTP identification
You must get used to identifying the Ethernet cabling through its pin assignment properly based on the Cat5 colored coding. Fig 3 shows UTP Cat5 pin assignment and wire coloring diagram. Actually there are two different standards:
 * 1) T568-A is for straight through UTP, both ends of RJ-45 connectors are the same.
 * 2) T568-B for cross-over UTP. Take a closer look at the crossover cabling, pin 2 and 6 and pin 1 and 3 are changed place.

Fig 3 Cat5 pin assignment and coloring diagram

Connecting devices
The figure 4 below shows the rule in interconnecting different devices using the UTP cable. For connecting different devices, use straight through cable. For interconnecting the same two devices, use crossover type cable.

Fig 4 interconnecting devices with UTP

Fiber optic Cable
Currently the latest transmission media in Ethernet standard technology is the fiber optic cable. This is the fastest transmission media used in LAN cabling with the following features Unfortunately, implementing fiber optic is very expensive.
 * 1) Longer distance can be run
 * 2) Less magnetic interference and yet makes more secure
 * 3) Can deliver the high speeds of up to 10Gbps

Fig. 5 Fiber Optic section diagram Optical devices can be divided into two types:
 * Multimode (MM), using a larger diameter size of optical fiber
 * Single-mode (SM), using a very small-diameter optical fiber. This type is more expensive due to a more precision manufacturing process. It allows a much longer distances and data rate than does MM fiber.

Optical connector
To transmit data over a fiber optic, you need a single strand of fiber for one direction. You need two pairs of strand for both direction – one direction for each. The typical connector for each end of strand cable is shown on the picture below.

Fig 6 Lan cable – Fiber optic connector

LAN Cabling Scenario
The figure below shows best practice how you can connect the two buildings, in this scenario uses UTP Cat5e for outdoor usage. By using UTP cross-over cable, you can connect to a trunk port to each switch. You need to configure the port as trunk ports to be functional. Figure 7 shows switch connection diagram with drop cable, and uplink cable.

Fig 7 Uplink and Drop cables A drop cable – a network cable connects any computer with switch. It should be Cat 5e UTP with each end of the cable is a RJ-45 connector. The minimum length is 0.6 meters and the maximum is 100 meters.

Best practices deployment
What is the more popular best practice LAN cabling between the computers and the switch? The picture shown below is a simple diagram how you can distribute the cables between switch to computers.

Fig 8 Patch panel diagram with punch down block Wall jack is a connection point, similar to a telephone jack that allows the computer to connect to the UTP – RJ-45. Patch cable is UTP cable segments that are used for connecting the network interface card to the wall jack or for connecting other portions of the cable installation Patch panel – a connection panel that provides multiple ports which in turn connects to other user devices or connectivity hardware such as a switch. You can implement best practices to each HR, Mining and Workshop buildings in the above scenario. To create a distribution LAN cabling easier to manage in the future if there is a network connection problem, you need to create a numbering system in patch panel for each connected cable to a wall jack. And also make sure you have a distribution list that records the data cable between the patch panel and the wall jack. Attach these registers near patch panels for future maintenance. Remember that rats often bite UTP cable, so the cable needs to be protected for example by putting it into the duct.

Coloring Scheme
The other thing to follow is by using coloring scheme:


 * **//function//** || **//Cable color//** ||
 * Data Cable -Cat 5e || Blue ||
 * Cross-over || Red ||
 * Phone / Voice || Grey ||
 * ISDN BRI WAN || Yellow – White ||