03 - Networking Media

8/12/2019 03 - Networking Media

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Networking Media


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Networking Media

Copper Media


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Cable Specifications

10BASE-T

10BASE5

10BASE2

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-100BASE-FX

1000BASE-T

1000BASE-SX

1000BASE-LX1000BASE-ZX

1000BASE-CWDM


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Coaxial Cable

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Coaxial Cable

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Coaxial cable advantages

It can be run longer distances than shielded twisted pair,STP, and unshielded twisted pair, UTP, cable without theneed for repeaters.

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Repeaters regenerate the signals in a network so that theycan cover greater distances.

Coaxial cable is less expensive than fiber-optic cable, andthe technology is well known.

It has been used for many years for many types of datacommunication, including cable television.


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Coaxial cable flaws

Problem with terminators and cable break.

Poor shield connection is one of the biggest sources of

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Connection problems result in electrical noise that interfereswith signal transmittal on the networking media.

For this reason thinnet is no longer commonly used nor

supported by latest standards (100 Mbps and higher) forEthernet networks.


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Shielded Twisted-Pair Cable

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Screened UTP (ScTP) = Foil Twisted Pair (FTP)

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It is usually 100-Ohm or 120-Ohm cable


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STP & ScTP installation issues

The metallic shielding materials in STP and ScTP need to be grounded

at both ends.

If improperly grounded or if there are any discontinuities in the entirelength of the shielding material, STP and ScTP become susceptible to

major noise problems.

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They are susceptible because they allow the shield to act like anantenna picking up unwanted signals.

Not only does the shield prevent incoming electromagnetic waves fromcausing noise on data wires, but it also minimizes the outgoing

radiated electromagnetic waves. These waves could cause noise inother devices.

The shielding materials make terminations more difficult andsusceptible to poor workmanship. However, STP and ScTP still have arole, especially in Europe.


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Unshielded Twisted Pair (UTP)

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Advantages

It is easy to install and is less expensive than other types ofnetworking media.

UTP costs less per meter than any other type of LAN cabling.

it has such a small external diameter,

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when UTP cable is installed using an RJ-45 connector, potentialsources of network noise are greatly reduced and a good solidconnection is practically guaranteed.

Disadvantages

UTP cable is more prone to electrical noise and interference than

other types of networking media,distance between signal boosts is shorter for UTP than it is forcoaxial and fiber optic cables.

Today, UTP is considered the fastest copper-based media.


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Two types of UTP cable:

Wall

Fly

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a egor es: 5

5e

6

305 meters of cable in one box


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UTP cable termination

UTP cable is

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RJ-45 connector

RJ-45 module


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Straight-through Cable

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Crossover Cable

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Rollover Cable

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Connecting to a Console Port

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Straight-through

CrossoverRollover


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Networking Media

Optical Media


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Visible spectrum

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Electromagnetic energy with wavelengths between 700 and 400 nm iscalled visible light.

Wavelengths that are not visible to the human eye are used to transmitdata over optical fiber. These wavelengths are slightly longer than redlight and are called infrared light.

The wavelength of the light in optical fiber is either 850 nm, 1310 nm, or1550 nm. These wavelengths were selected because they travel

through optical fiber better than other wavelengths.


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Reflection and Refraction

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Total Internal Reflection

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The following two conditions must be met for thelight rays in a fiber to be reflected back into thefiber without any loss due to refraction:

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The core of the optical fiber has to have a larger indexof refraction (n) than the material that surrounds it. Thematerial that surrounds the core of the fiber is calledthe cladding.

The angle of incidence of the light ray is greater thanthe critical angle for the core and its cladding.


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Numerical aperture

The numerical aperture of the fiber Thenumerical aperture of a core is the range

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the fiber that will be completely reflected.

Modes The paths which a light ray can

follow when traveling down a fiber


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Fiber

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Modes

There are a limited number of optical paths that alight ray can follow through the fiber.

These optical paths are called modes.

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If the diameter of the core of the fiber is largeenough so that there are many paths that lightcan take through the fiber, the fiber is calledmultimode fiber.

Single-mode fiber has a much smaller core thatonly allows light rays to travel along one modeinside the fiber


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Singlemode vs. multimode

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Fiber-Optic Connection

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Fiber-Optic Cable

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Transmission Devices

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Transmiters Multimode:

Infrared Light Emitting Diodes (LEDs) or Vertical Cavity

Surface Emitting Lasers (VCSELs) are two types of lightsource usually used with multimode fiber.

LEDs are a little cheaper to build and require somewhat

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.

However, LEDs cannot transmit light over cable as faras the lasers. Multimode fiber (62.5/125) can carry datadistances of up to 2000 meters (6,560 ft).

Wavelengths: 850nm & 1310nm

Singlemode:

IR lasers at 1310nm & 1550nm


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WARNING!

Never look at the near end of a fiber that isconnected to a device at the far end!

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,

switch, or router!

Remember to keep protective covers over

the ends of fiber and inserted into thefiber-optic ports of switches and routers!

Be very careful!


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Receivers

p-intrinsic-n diodes (PIN photodiodes).

PIN photodiodes are manufactured to besensitive to 850, 1310, or 1550 nm of light that

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the fiber. When struck by a pulse of light at the proper

wavelength, the PIN photodiode quicklyproduces an electric current of the propervoltage for the network.


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Optical Connectors

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Optical Link Loss Budget

When a fiber-optic link is being planned, the amount of signal power

loss that can be tolerated must be calculated. This is referred to as theoptical link loss budget. The decibel (dB) is the unit used to measure

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Two of the most important instruments for testing fiber links areOptical Loss Meters and Optical Time Domain Reflectometers (OTDRs).

These instruments both test optical cable to ensure that the cablemeets the TIA standards for fiber. They also test to verify that the link

power loss does not fall below the optical link loss budget. OTDRs canprovide much additional detailed diagnostic information about a fiberlink. They can be used to troubleshoot a link when problems occur.


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Calibrated Light Sources and Light Meter

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Networking Media

Wireless Media


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Wireless LAN Standards

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IEEE is the prime issuer of standards for wireless networks.

The standards have been created within the framework of theregulations created by the Federal CommunicationsCommission (FCC).

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Direct Sequence Spread Spectrum (DSSS). DSSS applies towireless devices operating within a 1 to 2 Mbps

The next standard approved was 802.11b, which increasedtransmission capabilities to 11 Mbps.

802.11b devices achieve the higher data throughput rate byusing a different coding technique from 802.11


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802.11a covers WLAN devices operating in the 5 GHZ transmissionband. Using the 5 GHZ range disallows interoperability of 802.11bdevices as they operate within 2.4 GHZ.

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.proprietary technology known as "rate doubling" has achieved 108Mbps. In production networks, a more standard rating is 20-26 Mbps.

802.11g provides the same throughout as 802.11a but with backwardscompatibility for 802.11b devices using Othogonal Frequency DivisionMultiplexing (OFDM) modulation technology.

Cisco has developed an access point that permits 802.11b and 802.11adevices to coexist on the same WLAN. The access point suppliesgateway services allowing these otherwise incompatible devices tocommunicate.


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Internal Wireless NIC for Desktop or Server

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PCMCIA NIC for Laptop

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External USB Wireless NIC

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Access Point

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Infrastructure Mode

When a client is activated within the WLAN, it will start "listening" for a

compatible device with which to "associate". This is referred to as"scanning" and may be active or passive.

Active scanning causes a probe request to be sent from the wireless

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Service Set Identifier (SSID) of the network it wishes to join. When anAP with the same SSID is found, the AP will issue a probe response.The authentication and association steps are completed.

Passive scanning nodes listen for beacon management frames(beacons), which are transmitted by the AP (infrastructure mode) orpeer nodes (ad hoc). When a node receives a beacon that contains theSSID of the network it is trying to join, an attempt is made to join thenetwork. Passive scanning is a continuous process and nodes mayassociate or disassociate with APs as signal strength changes.


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Wireless LAN

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Depending on the structural composition of the location in which the APis installed and the size and gain of the antennae, the size of the cell couldgreatly vary. Most commonly, the range will be from 91.44 to 152.4 meters

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03 - Networking Media