+ transmission media. + local area networks lans consist of transmission media and network nodes....
TRANSCRIPT
+
Transmission Media
+Local Area Networks
• LANs consist of Transmission media and network nodes.
• Transmission media is a pathway that carries the information from sender to receiver .
• We use different types of cables or waves to transmit data.
+Types of Transmission Media
Transmission media is broadly classified into two groups. 1. Wired or Guided Media or Bound Transmission Media 2. Wireless or Unguided Media or Unbound Transmission
Media
+Wired or Guided Media or Bound Transmission Media
Bound transmission media are the cables that are tangible or have physical existence and are limited by the physical geography.
Popular bound transmission media in use are twisted pair cable, co-axial cable and fiber optical cable.
Each of them has its own characteristics like transmission speed, effect of noise, physical appearance, cost etc.
+Wireless or Unguided Media or Unbound Transmission Media
Unbound transmission media are the ways of transmitting data without using any cables.
These media are not bounded by physical geography.
This type of transmission is called Wireless communication..
Wireless channels can be divided based on wave frequency Microwave Infrared Laser
+Microwave
Used to send signals between 30m-100m inside buildings, and 100m-300m outside.
Microwave can travel through walls or any type of barriers that disallow wired or fixed transmission media.
It can be affected by Electromagnetic Interferences and noise.
Signals and waves propagate in all the directions around Omnidirectional from (aerial: special device) attached to NIC or any network devices
+Infrared
Can send data through limited area inside the building
Infrared have high speed transmission rate between PCs and\or other devices in LAN such as printer.
Can NOT go through walls or any barriers.
It does NOT affected by noise and interference with any electromagnetic waves. Infrared signals affected by Sun light.
Unidirectional, Diffused
+Laser
Can NOT go through walls or barriers or fog or heavy rain.
It does NOT affected by noise and Electromagnetic Interference. It affected by Sun Light.
Laser signals may curve, bend if affected by high temperature.
Laser is Unidirectional.
+Connectors
Connectors Hardware pieces connecting wire to network device Every networking medium requires a specific kind of connector The type of connector you use affect the cost of
Installing and maintaining network Ease of adding new segments or nodes Technical expertise required to maintain network
9
+Media Converters
Connectors are specific to a particular media type, but that doesn’t prevent one network from using multiple media.
Some connectivity devices are designed to accept more than one type of media.
If not, we can integrate the two media types by using media converters.
Media converter A piece of hardware enabling networks or segments running on
different media to interconnect and exchange signals
10
+ 11
Figure 3-15 Copper wire-to-fiber media converter
+Coaxial Cable
Coaxial cable consists of a central metal core (often copper) surrounded by: Insulator Braided metal shielding (braiding or shield) Outer cover (sheath or jacket)
12
carries the electromagnetic signal
acts as both a shield against noise and a ground for the signal
protects the cable from physical damage
+Coaxial Cable (cont’d.)
Because of its shielding, it has high noise resistance to noise
Advantage over twisted pair cabling Carry signals farther before amplifier required
Disadvantage over twisted pair cabling More expensive
Hundreds of specifications Differences between the cable types: shielding and conducting
cores which influence their transmission characteristics Each type of coax is suited to a different purpose. All types have been assigned an RG specification number.
13
+Coaxial Cable (cont’d.)
When discussing the size of the conducting core: American Wire Gauge (AWG) size Larger AWG size, smaller wire diameter
Data networks usage RG-6 : to deliver broadband cable Internet service and cable TV,
particularly over long distances RG-8: 10Base-5 Ethernet (old) RG-58: is more flexible and easier to handle and install, 10Base-2 (old) RG-59: used for relatively short connections,
14
+Coaxial Cable (cont’d.)
The two coaxial cable types commonly used in networks today, RG-6 and RG-59, can terminate with one of two connector types: an F-type connector or a BNC connector
15
Figure 3-17 F-Type connector Figure 3-18 BNC connector
+Twisted Pair Cable
Twisted pair cable consists of color-coded insulated copper wire pairs Every two wires are twisted around each other to form pairs all the pairs are encased in a plastic sheath The number of pairs in a cable varies, depending on the cable type
16
Figure 3-19 Twisted pair cable
+Twisted Pair Cable (cont’d.)
The more wire pair twists per foot The more resistance the pair to cross talk Higher-quality More expensive twisted pair cable
Twist ratio The number of twists per meter or foot
High twist ratio Greater attenuation
17
+Twisted Pair Cable (cont’d.)
Because twisted pair is used in such a wide variety of environments and for a variety of purposes, it comes in hundreds of different designs These designs vary in their twist ratio, number of wire pairs, copper grade,
shielding type, shielding materials A twisted pair cable may contain from1 to 4200 wire pairs possible Modern networks typically use cables that contain four wire pairs, in which
one pair is dedicated to sending data and another pair is dedicated to receiving data
Wiring standard specification TIA/EIA 568
Most common twisted pair types Category (cat) 3, 5, 5e, 6, 6a, 7 CAT 5 or higher used in modern LANs
18
+Twisted Pair Cable (cont’d.)
Advantages Relatively inexpensive Flexible Easy installation Spans significant distance before requiring repeater (though not as far as coax). Accommodates several different topologies, although it is most often implemented
in star or star-hybrid topologies.
Two categories Shielded twisted pair (STP) Unshielded twisted pair (UTP)
19
+STP (Shielded Twisted Pair)
STP (shielded twisted pair) cable consists of twisted wire pairs that are not only Individually insulated but also surrounded by metallic substance shielding (foil) The shielding acts as a barrier to external electromagnetic forces It also contains electrical energy of signals inside May be grounded to enhance its protective effects
20
Figure 3-20 STP cable
+UTP (Unshielded Twisted Pair)
UTP (unshielded twisted pair) cabling consists of one or more insulated wire pairs encased in plastic sheath UTP doesn’t contain additional shielding for the twisted pairs
As a result, UTP is both less expensive, less noise resistance than STP
21
Figure 3-21 UTP cable
+Comparing STP and UTP
Throughput STP and UTP can transmit the same rates
Cost STP and UTP vary
Connector STP and UTP use Registered Jack 45 (RJ 45) Telephone connections use Registered Jack 11 (RJ 11)
22
+Comparing STP and UTP (cont’d.)
Noise immunity STP more noise resistant
Size and scalability Maximum segment length for both: 100 meters
23
+Terminating Twisted Pair Cable
Patch cable Relatively short cable ( usually between 3 and 25 feet) Connectors at both ends
Proper cable termination techniques Basic requirement for two nodes to communicate
Poor terminations: Lead to loss or noise
TIA/EIA has specified two different methods of inserting twisted pair wires into RJ-45 plugs TIA/EIA 568A TIA/EIA 568B
24
+ 25
Figure 3-24 TIA/EIA 568A standard terminations
Figure 3-25 TIA/EIA 568B standard terminations
Functionally, there is no difference between the standards. You only have to be certain that you use the same standard on every RJ-45 plug and jack on your network, so that data is transmitted and received correctly
+Terminating Twisted Pair Cable (cont’d.)
Straight-through cable Terminate RJ-45 plugs at both ends identically following one of the
TIA/EIA 568 standards used to connect a workstation to a hub or router
Crossover cable Transmit and receive wires on one end reversed to connect two workstations without using a connectivity device or to
connect two hubs through their data ports
26
Figure 3-26 RJ-45 terminations on a crossover cable
+Terminating Twisted Pair Cable (cont’d.)
Termination tools Wire cutter Wire stripper Crimping tool
After making cables: Verify data transmit and receive
27
+Fiber-Optic Cable
Fiber-optic cable (fiber) One or more glass or plastic fibers at its center (core)
Data transmission Pulsing light sent from laser or light-emitting diode (LED) through central
fibers
Cladding Layer of glass or plastic surrounding fibers Different density from glass or plastic in strands Reflects light back to core in patterns that vary depending on the
transmission mode Allows fiber to bend
28
+Fiber-Optic Cable (cont’d.)
Plastic buffer outside cladding Protects cladding and core Opaque to absorb escaping light Surrounded by Kevlar (polymeric fiber) strands to prevent the cable
from stretching, and to protect the inner core further
Plastic sheath covers Kevlar strands
29
Figure 3-30 A fiber-optic cable
+Fiber-Optic Cable (cont’d.)
Different varieties Based on intended use and manufacturer
30
Figure 3-31 Zipcord fiber-optic patch cable
Courtesy Course Technology/Cengage Learning
+Fiber-Optic Cable (cont’d.)
Benefits over copper cabling Extremely high throughput Very high noise resistance Excellent security Able to carry signals for longer distances Industry standard for high-speed networking
Drawbacks More expensive than twisted pair cable Requires special equipment to splice
31
+SMF (Single-Mode Fiber)
Consists of narrow core (8-10 microns in diameter) Laser-generated light travels over one path
Little reflection Light does not disperse as signal travels
Can carry signals many miles: Before repeating required
Rarely used for shorter connections Due to cost
32
+MMF (Multimode Fiber)
Contains core with larger diameter than single-mode fiber Common sizes: 50 or 62.5 microns
Laser or LED generated light pulses travel at different angles
Greater attenuation than single-mode fiber
Common uses Cables connecting router to a switch Cables connecting server on network backbone
33
+Fiber-Optic Converters
Required to connect multimode fiber networks to single-mode fiber networks Also fiber- and copper-based parts of a network
34
Figure 3-38 Single-mode to multimode converter
Courtesy Omnitron Systems Technology
+Serial Cables
Data transmission style Pulses issued sequentially, not simultaneously
Serial transmission method RS-232
Uses DB-9, DB-25, and RJ-45 connectors
35
+Structured Cabling
Cable plant Hardware that makes up the enterprise cabling system
Cabling standard TIA/EIA’s joint 568 Commercial Building Wiring Standard
Also known as structured cabling Based on hierarchical design
36
37
Figure 3-42 TIA/EIA structured cabling in an enterprise
Courtesy Course Technology/Cengage Learning
38
Intermediate Distribution Frame
TelecomClosets
39
40
+Structured Cabling (cont’d.)
Components Entrance facilities MDF (main distribution frame) Cross-connect facilities IDF (intermediate distribution frame) Backbone wiring Telecommunications closet Horizontal wiring Work area
41
+Structured Cabling (cont’d.)
Entrance facilities: The entrance facility is the point where the outdoor cable
connects with the building’s backbone cabling. This is usually the demarcation point between the service
provider and the customer owned systems.
MDF (main distribution frame) Sometimes the MDF is simply known as the computer room
or equipment room. First point in the network where LAN is connected with the
service provider. MDF requires equipment capable of great throughput.
42
43
+Structured Cabling (cont’d.)
Cross-connect facilities— The points where circuits interconnect with other circuits.
Cross-connect devices allow large numbers of conducting wires to be mechanically interconnected in an organized fashion.
There are two types of cross-connect devices: Punch-down blocks and Patch panels
A punch-down block is a panel of data receptors into which twisted pair wire is inserted, or punched down, to complete a circuit.
From a punch-down block, wires are distributed to a patch panel, a wall-mounted panel of data receptors.
44
45
+Structured Cabling (cont’d.)
IDF (intermediate distribution frame)— A junction point between the MDF and concentrations of fewer
connections
Backbone wiring The cables or wireless links that provide interconnection between
entrance facilities and MDFs, MDFs and IDFs, and IDFs and telecommunications closets.
One component of the backbone is given a special term: vertical cross-connect.
A vertical cross-connect runs between a building’s floors. For example, it might connect an MDF and IDF or IDFs and telecommunications closets within a building.
The TIA/EIA standard designates distance limitations for backbones of varying cable types, as specified in Table
46
+Structured Cabling (cont’d.)
47
Table 3-2 TIA/EIA specifications for backbone cabling
Courtesy Course Technology/Cengage Learning
+Structured Cabling (cont’d.)
Telecommunications closet Also known as a “telco room,” it contains connectivity for
groups of workstations in its area, plus cross-connections to IDFs or, in smaller organizations, an MDF.
Large organizations may have several telco rooms per floor, but the TIA/EIA standard specifies at least one per floor.
Telecommunications closets typically house patch panels, punch-down blocks, and connectivity devices for a work area.
Because telecommunications closets are usually small, enclosed spaces, good cooling and ventilation systems are important to maintaining a constant temperature.
48
+Structured Cabling (cont’d.)
Horizontal wiring This is the wiring that connects workstations to the closest
telecommunications closet. TIA/EIA recognizes three possible cabling types for
horizontal wiring: STP, UTP, or fiber-optic cable. The maximum allowable distance for horizontal wiring is
100 m. This span includes 90 m to connect a data jack on the wall to the telecommunications closet plus a maximum of 10 m to connect a workstation to the data jack on the wall.
49
50
<= 10
+Structured Cabling (cont’d.)
Work area An area that encompasses all patch cables and horizontal
wiring necessary to connect workstations, printers, and other network devices from their NICs to the telecommunications closet.
The TIA/EIA standard calls for each wall jack to contain at least one voice and one data outlet.
Realistically, you will encounter a variety of wall jacks.
51