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E6032 COMPUTER NETWORKINGPn. Fazida Adlan
PSSAAS
JKE
What is Computer Networking? Computer Networking is the joining of two or
more computers in order for them to communicate or jointly access a server. They can be joined permanently via fixed cables or via modems.
Networking is the practice of linking computing devices together with hardware and software that supports data communications across these devices.
You can use this kind of network to share files, a printer or another peripheral device, and even an Internet connection. To connect two computers for sharing network resources, consider these alternatives.
Characteristics and advantages of a Computer
Network The primary purpose of a computer network
is to share resources: Play a CD music from one computer while
sitting on another computer You may have a computer with a CD writer
or a backup system but the other computer doesn’t have it; In this case, you can burn CDs or make backups on a computer that has one of these but using data from a computer that doesn’t have a CD writer or a backup system
You may have a computer that doesn’t have a DVD player. In this case, you can place a movie DVD on the computer that has a DVD player, and then view the movie on a computer that lacks a DVD player
Continue…
You can connect a printer (or a scanner, or a fax machine) to one computer and let other computers of the network print (or scan, or fax) to that printer (or scanner, or fax machine)
You can place a CD with pictures on one computer and let other computers access those pictures
You can create files and store them in one computer, then access those files from the other computer(s) connected to it
Examples of network
A computer network can be two computers connected:
A computer network can also consist of, and is usually made for, more than two computers
Categorizes of users in cn Highly Managed
Configuration for process workers - requires highly restricted configurations - few applications. Suitable for marketing, processing claims and loans, and serving customers.
A highly managed desktop has the following characteristics:
Users working different shifts can share the computer. Each user needs a unique logon account.
Users can customize a limited number of application-specific settings.
Users can access their data from any computer.
User data is stored on server shares, and users do not store data locally
Categorizes of users in cn Lightly Managed
Requires a lot of control over their computers, in an organization where highly managed desktops are not acceptable to users, or where desktop management is highly delegated.
The lightly managed desktop has a minimal set of restrictions that help reduce desktop support costs and user down time:
Users can customize most settings that affect them but are prevented from making unauthorized system changes.
Users can log on to any computer on the network and access their data.
User data is saved on server shares and is not stored locally.
Categorizes of users in cn Mobile User
A mobile user configuration is appropriate for managing mobile users — travelling users who often use portable computers. Mobile users typically log on to the same computer, and they connect by both high speed and low speed.
The following characteristics apply to mobile-user desktops:
Can be configured so that users have access to user data whether the computer is connected to or not connected to the network.
Can save data locally or on network servers.
Can be configured so that users can disconnect from the network without logging off or shutting down, and to have data files synchronized automatically.
Categorizes of users in cn Multiuser
The multiuser desktop is appropriate for environments such as a university laboratory, public computing center, or a library where users might be allowed to save some customizations, such as desktop wallpaper and color scheme preferences, but are prevented from changing hardware or connection settings.
A multiuser configuration has the following characteristics: The system is mostly restricted, but some personal settings
are allowed. Users can log on and use a configured roaming profile. Users share this computer with other users either by having
a unique logon account or by using a Guest account. User data is saved on server shares, and users do not store
data locally.
Categorizes of users in cn Kiosk
The term kiosk in this context refers to a public workstation that runs only one application and one user account, runs unattended, and automatically logs on. Users are unknown to the kiosk owner and do not provide logon credentials. A kiosk workstation is highly secure, simple to operate. Users can not change the default settings.
Use the kiosk desktop in a public area where multiple users access the computer or where you want to prevent users from making any customizations. For example, the kiosk is frequently used in airports where passengers check in and view their flight information.
The following characteristics apply to the kiosk desktop: The system is highly restricted by applying policy settings.
Users cannot customize the installed applications. Users cannot save data to the computer locally or to the
network. The computer can be in a stand-alone environment without any
network connectivity. Users cannot add or remove applications. Users are anonymous, and all users share the same user
account.
Categorizes of users in Computer Network
Task Station
Use the task station desktop — an entry terminal for orders on a manufacturing floor or in a call center, for example — for data entry workers when you need dedicated computers to run a single application.
A task station configuration has the following characteristics:
The computer is dedicated to running a single application.
Users on different shifts often share computers.
Each user has a unique logon account.
Many users roam between multiple computers that run the same single application.
User data is saved on server shares and can be stored locally.
Types of network - LAN
Types of network - MAN
Types of network - WAN
What is intranet?
An intranet is a private network that is contained within an enterprise. It may consist of many interlinked local area networks and also use leased lines in the wide area network. Typically, an intranet includes connections through one or more gateway computers to the outside Internet. The main purpose of an intranet is to share company information and computing resources among employees. An intranet can also be used to facilitate working in groups and for teleconferences.
And what is internet?
•The Internet is a global system of interconnected computer networks that interchange data by packet switching using the standardized Internet Protocol Suite (TCP/IP). •It is a "network of networks" that consists of millions of private and public, academic, business, and government networks of local to global scope.•Linked by copper wires, fibre optic cables, wireless connections, and other technologies.
Client and Server Computer
A client is an application or system that accesses a remote service on another computer system, known as a server, by way of a network. The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network. These dumb terminals were clients of the time-sharing mainframe computer.
A server is a computer program that provides services to other computer programs (and their users), in the same or other computer. The physical computer that runs a server program is also often referred to as server.
Characteristics of a client Initiates requests Waits for replies Receives replies Usually connects to a small number of
servers at one time Typically interacts directly with end-users
using a graphical user interface
Characteristics of a server Never initiates requests or activities Waits for and replies to requests from
connected clients A server can remotely install/uninstall
applications and transfer data to the intended clients
Peer to peer (p2p) A peer-to-peer (or P2P) computer network uses
diverse connectivity between participants in a network.
P2P networks are typically used for connecting nodes via largely ad hoc connections. Such networks are useful for many purposes. Sharing content files (see file sharing) containing audio, video, data or anything in digital format is very common, and real time data, such as telephony traffic, is also passed using P2P technology.
A pure P2P network does not have the notion of clients or servers but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network.
This model of network arrangement differs from the client-server model where communication is usually to and from a central server.
P2P Networking Illustration Client Server Networking
Advantages of Client Server Network
In most cases, a client-server architecture enables the roles and responsibilities of a computing system to be distributed among several independent computers that are known to each other only through a network. This creates an additional advantage to this architecture: greater ease of maintenance. For example, it is possible to replace, repair, upgrade, or even relocate a server while its clients remain both unaware and unaffected by that change. This independence from change is also referred to as encapsulation.
All the data is stored on the servers, which generally have far greater security controls than most clients. Servers can better control access and resources, to guarantee that only those clients with the appropriate permissions may access and change data.
Since data storage is centralized, updates to that data are far easier to administer than what would be possible under a P2P paradigm. Under a P2P architecture, data updates may need to be distributed and applied to each "peer" in the network, which is both time-consuming and error-prone, as there can be thousands or even millions of peers.
Many mature client-server technologies are already available which were designed to ensure security, 'friendliness' of the user interface, and ease of use.
It functions with multiple different clients of different capabilities.
Advantages of Client Server Network
Disadvantages of CSN vs. P2P
Traffic congestion on the network has been an issue since the inception of the client-server paradigm.
As the number of simultaneous client requests to a given server increases, the server can become severely overloaded.
Contrast that to a P2P network, where its bandwidth actually increases as more nodes are added, since the P2P network's overall bandwidth can be roughly computed as the sum of the bandwidths of every node in that network.
The client-server paradigm lacks the robustness of a good P2P network.
Under client-server, should a critical server fail, clients’ requests cannot be fulfilled.
In P2P networks, resources are usually distributed among many nodes. Even if one or more nodes depart and abandon a downloading file, for example, the remaining nodes should still have the data needed to complete the download
Disadvantages of CSN vs. P2P
PHYSICAL TOPOLOGIES OF LAN
Network topology is the study of the arrangement or mapping of the elements(links, nodes) of a network, especially the physical (real) and logical (virtual) interconnections between nodes.[
A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology.
Any given node in the LAN will have one or more links to one or more other nodes in the network and the mapping of these links and nodes onto a graph results in a geometrical shape that determines the physical topology of the network.
Likewise, the mapping of the flow of data between the nodes in the network determines the logical topology of the network.
The physical and logical topologies might be identical in any particular network but they also may be different.
Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ in two networks and yet their topologies may be identical.
PHYSICAL TOPOLOGIES OF LAN
LAN TOPOLOGY : BUS
All nodes on the LAN are connected by one linear cable - called the shared medium.
Every node on this cable segment sees transmissions from every other station on the same segment.
At each end of the bus is a terminator, which absorbs any signal, removing it from the bus.
Ethernet (IEEE 802.3) is the protocols used for this type of LAN.
LAN TOPOLOGY: BUS
Advantages: Easy to remove or extend network Easy to set up network Easy to manage the physical wired used in
network Disadvantages:
Slow transmission of data – one by one If the main cable down, whole network
down
LAN TOPOLOGY : STAR
All stations are connected by cable (or wireless) to a central point, such as hub or a switch.
If the central node is operating in a broadcast fashion such as a Hub, transmission of a frame from one station to the node is retransmitted on all of the outgoing links.
In this case, although the arrangement is physically a star, it is logically a bus.
In the case of the central node acting as switch, an incoming frame is processed in the node and then retransmitted on an outgoing link to the destination station.
Ethernet protocols (IEEE 802.3) are often used in the Star topology LAN.
LAN TOPOLOGY: STAR
Advantages : Fast transmission Easy to remove or expand
Disadvantages : Central Point down, network down Cost high
LAN TOPOLOGY : RING
All nodes on the LAN are connected in a loop and their Network Interface Cards (NIC) are working as repeaters.
There is no starting or ending point. Each node will repeat any signal that is on the network regardless its destination.
The destination station recognizes its address and copies the frame into a local buffer as it goes by.
The frame continues to circulate until it returns to the source station, where it is removed.
Token Ring (IEEE 802.5) is the most popular Ring topology protocol. FDDI (IEEE 802.6) is another protocol used in the Ring topology, which is based on the Token Ring.
Advantages: All nodes on the network have equal
chance of transmitting data.
Growth of system has minimal impact on performance.
Disadvantages: If one of the nodes ones down then the
whole network may go down. Difficult to add and delete nodes to
/from the ring.
LAN TOPOLOGY : RING
LAN TOPOLOGY : TREE
Tree: The tree topology is a logical extension of the bus topology.
The transmission medium is a branching cable with no closed loops.
The tree layout begins at a point called the head-end, where one or more cables start, and each of these may have branches.
The branches in turn may have additional branches to allow quite complex layouts.
LAN TOPOLOGY : TREE
Advantages of a Tree Topology Point-to-point wiring for individual
segments. Supported by several hardware
and software venders. Disadvantages of a Tree
Topology Overall length of each segment is
limited by the type of cabling used. If the backbone line breaks, the
entire segment goes down. More difficult to configure and wire
than other topologies.
LOGICAL TOPOLOGY
Also called signal topology. The way that the devices on a network are
arranged and how they communicate - called the physical topology.
Logical topology, in contrast, is the way that the signals act on the network media
the way data passes through network from one device to the next without regard to the physical interconnection of the devices.
LOGICAL TOPOLOGY
Logical topologies are bound to the network protocols that direct how the data moves across a network. The Ethernet protocol is a common logical bus topology protocol.
Token Ring is a common logical ring topology protocol.
A network's logical topology is not necessarily the same as its physical topology.
For example, twisted pair Ethernet is a logical bus topology in a physical star topology layout.
NETWORKING DEVICES
a. Network Interface Card / Network Adaptor (NIC)
b. Repeaters c. Hubs d. Bridges e. Switches f. Bridge Modem
NETWORK INTERFACE CARD - NIC Also known as network card, network
adapter, network interface controller (NIC), network interface card, or LAN adapter.
computer hardware - designed to allow computers to communicate over a computer network.
It is both an OSI layer 1 (physical layer) and layer 2 (data link layer) device
Provides physical access to a networking medium and provides a low-level addressing system through the use of MAC addresses.
It allows users to connect to each other either by using cables or wirelessly.
NETWORK INTERFACE CARD
NETWORK INTERFACE CARD
NETWORK INTERFACE CARD
Network card typically has a twisted pair, BNC, or AUI socket where the network cable is connected,
A few LEDs to inform the user of whether the network is active, and whether or not there is data being transmitted on it.
Network Cards are typically available in 10/100/1000 Mbit/s varieties.
Meaning they can support a transfer rate of 10, 100 or 1000 Megabits per second.
BNC AND AUI CONNECTORS
REPEATER
A network repeater is a device used to expand the boundaries of a wired or wireless (WiFi) local area network (LAN).
In the past, wired network repeaters were used to join segments of Ethernet cable.
The repeaters would amplify the data signals before sending them on to the uplinked segment, thereby countering signal decay that occurs over extended lengths of wire.
REPEATER
A WiFi network repeater will pick up the signal from a wireless router and amplify it, propagating signal strength to boost distance and coverage of the WLAN.
For example, assume an upstairs office gets only a weak signal from a router located in the basement.
The building might have a steel infrastructure, cordless phones and other forms of interference. One option is to relocate the router on another floor to see if the entire building can be covered, but this isn’t always convenient.
REPEATER
Transmits information by receiving the information on one cable segment - repeating the received information onto the other cable segment to which it is attached.
may perform a variety of signal processing operations on the received data before it is repeated, such as signal amplification, signal retiming, preamble insertion, etc.
Repeaters in LANs are simple devices for broadcasting data packets originating at one port of the repeater to all other ports
REPEATER
A network repeater typically has four, eight, or sixteen ports.
Any transmission to any of the ports is repeated to all the other ports on the repeater
Performs signal amplitude and timing restoration on an incoming bit stream and repeats the bit stream to all of the ports connected
By repeating data to all ports - acts as a logical coaxial cable so that any node connected to the network will see another node's transmission.
Multiport repeaters, also referred to as hubs or wiring concentrators, allow interconnection of a number of network segments at the physical layer of the network protocol.
HUB
A common connection point for devices in a network. Commonly used to connect segments of a LAN. Contains multiple ports. When a packet arrives at one port, it is copied to the
other ports so that all segments of the LAN can see all packets.
A passive hub serves simply as a conduit for the data, enabling it to go from one device (or segment) to another.
Intelligent hubs - enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub. Intelligent hubs are also called manageable hubs.
Switching hub, actually reads the destination address of each packet and then forwards the packet to the correct port.
HUB
HUB
BRIDGE
A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model.
Bridges are similar to repeaters or network hubs, devices that connect network segments at the physical layer;
However, with bridging, traffic from one network is managed rather than simply rebroadcast to adjacent network segments.
In Ethernet networks, the term "bridge" formally means a device that behaves according to the IEEE 802.1D
Bridges tend to be more complex than hubs or repeaters due to the fact that bridges are capable of analyzing incoming data packets on a network to determine if the bridge is able to send the given packet to another segment of that same network.
ADVANTAGES OF BRIDGE
Self configuring Primitive bridges are often inexpensive Reduce size of collision domain by
microsegmentation in non switched networks Transparent to protocols above the MAC layer Allows the introduction of management -
performance information and access control LANs interconnected are separate and physical
constraints such as number of stations, repeaters and segment length don't apply
it also helps minimize high bandwidth
DISADVANTAGES OF BRIDGE
Does not limit the scope of broadcasts Does not scale to extremely large networks Buffering introduces store and forward delays -
on average traffic destined for bridge will be related to the number of stations on the rest of the LAN
Bridging of different MAC protocols introduces errors
Because bridges do more than repeaters by viewing MAC addresses, the extra processing makes them slower than repeaters
Bridges are more expensive than repeaters
SWITCHES
A network switch is a small hardware device that joins multiple computers together within one local area network (LAN).
Operate at layer two (Data Link Layer) of the OSI model. Identical to network hubs, but a switch generally
contains more intelligence (and a slightly higher price tag) than a hub.
Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately.
By delivering messages only to the connected device intended, a network switch conserves network bandwidth and offers generally better performance than a hub.
SWITCHES
A switch is effectively a higher-performance alternative to a hub
hubs operate using a broadcast model and switches operate using a virtual circuit model. When four computers are connected to a hub, for example, and two of those computers communicate with each other, hubs simply pass through all network traffic to each of the four computers. Switches, on the other hand, are capable of determining the destination of each individual traffic element (such as an Ethernet frame) and selectively forwarding data to the one computer that actually needs it. By generating less network traffic in delivering messages, a switch performs better than a hub on busy networks.
BRIDGE MODEM
Identical to basic bridge functions including dividing a network to LANs
Capable of functioning as a modem or able to be used as a modem instead as only a bridge.
Chapter 3: DATA TRANSMISSION
A continuously varying signal or wave. susceptible to interference which can change the
character of the wave. An analog or analogue signal is any continuous
signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity
It differs from a digital signal in that small fluctuations in the signal are meaningful
Analog is usually thought of in an electrical context; however, mechanical, pneumatic, hydraulic, and other systems may also convey analog signals.
analogue signal can be thought of as a simulation or duplication of one continuous time varying quantity in another, possibly different, time varying quantity.
What is Analogue Data?
A signal that takes on only two values, off or on, typically represented by "0" or "1." Digital signals require less power but (typically) more bandwidth than analog.
It can refer to discrete-time signals that have a discrete number of levels, for example a sampled and quantified analog signal, or to the continuous-time waveform signals in a digital system, representing a bit-stream
What is Digital Data?
•A waveform that switches between two voltage levels •Represent two states of a Boolean value (0 and 1) is referred to as a digital signal, even though it is an analog voltage waveform, since it is interpreted in terms of only two levels.
What is Digital Data?
•The clock signal is a special digital signal •The image shown can be considered the waveform of a clock signal. •The given diagram is an example of the practical pulse and therefore we have introduced two new terms that are:•Rising edge: the transition from a low voltage (level 1 in the diagram) to a high voltage (level 2). •Falling edge: the transition from a high voltage to a low one.
Binary files are usually thought of as being a sequence of bytes, which means the binary digits (bits) are grouped in eights.
Binary files typically contain bytes that are intended to be interpreted as something other than text characters.
binary files can also contain images, sounds, compressed versions of other files.
What is Binary?
Example of Binary File
What Bit Rate? the number of bits that are conveyed or
processed per unit of time. The bit rate is quantified using the bits
per second (bit/s or bps) In digital communication systems, the
gross bitrate, raw bitrate, line rate or data signaling rate is the total number of physically transferred bits per second over a communication link, including useful data as well as protocol overhead.
Bit Rate n Bandwidth
Bit Rate n Bandwidth
Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum, and is typically measured in hertz. In case of a baseband channel or signal, the bandwidth is equal to its upper cutoff frequency.
Bandwidth (computing) or digital bandwidth: a rate of data transfer, throughput or bit rate, measured in bits per second
Bandwidth (signal processing) or analog bandwidth: a measure of the width of a range of frequencies, measured in hertz
Bandwidth
In computer networking and computer science, digital bandwidth, network bandwidth or just bandwidth is a measure of available or consumed data communication resources expressed in bit/s or multiples of it (kbit/s, Mbit/s etc).
Bandwidth may refer to bandwidth capacity or available bandwidth in bit/s, which typically means the net bit rate or the maximum throughput of a logical or physical communication path in a digital communication system. The reason for this usage is that according to Hartley's law, the maximum data rate of a physical communication link is proportional to its bandwidth in hertz, which is sometimes called "analog bandwidth“.
Baud vs Bit Rate
The baud rate of a data communications system is the number of symbols per second transferred.
A symbol may have more than two states, so it may represent more than one binary bit (a binary bit always represents exactly two states).
Baud means "state changes of the line per second“
modulation rate or the number of times per second that a line changes state
Baud Rate
Named after J. M. Emile Baudot (1845-1903), who was a French telegraph operator, who worked out a five-level code (five bits per character) for telegraphs
It was standardized as International Telegraph Alphabet Number 2, and is commonly called Baudot
Since 2^5 is only 32 and the uppercase letters, numbers, and a few punctuation characters add to more than that, Baudot uses Shift In and Shift Out characters (analogous to how the Caps Lock key on a PC keyboard reduces the number of keys needed by enabling each letter key to represent two characters).
Bit Rate
the bit rate is the number of bits that pass a given point in a telecommunication network in a given amount of time, usually a second. Thus, a bit rate is usually measured in some multiple of bits per second - for example, kilobits, or thousands of bits per second (Kbps). The term bit rate is a synonym for data transfer rate (or simply data rate).
TWISTED PAIR
A type of cable that consists of two independently insulated wires twisted around one another.
The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction
TWISTED PAIR
two wires carry equal and opposite signals and the destination detects the difference between the two.
This is known as differential mode transmission.
Noise sources introduce signals into the wires by coupling of electric or magnetic fields and tend to couple to both wires equally.
Produces a common-mode signal which is cancelled at the receiver when the difference signal is taken
TWISTED PAIR
One pair can induce crosstalk in another and it is additive along the length of the cable.
Twisting the pairs counters this effect . The twist rate also called pitch of the
twist, usually defined in twists per meter.
Coaxial Cable
Coaxial cable - copper cable used by cable TV companies between the community antenna and user homes and businesses.
Called "coaxial" because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis.
The outer channel serves as a ground. Many of these cables or pairs of coaxial tubes can be placed in a single outer sheathing and, with repeaters, can carry information for a great distance.
Coaxial cable was invented in 1929 and first used commercially in 1941
Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength and cost.
The inner conductor might be solid or stranded; stranded is more flexible.
To get better high-frequency performance, the inner conductor may be silver plated. Sometimes copper-plated iron wire is used as an inner conductor
Fiber Optic
A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. Advantages :
have a much greater bandwidth than metal cables. This means that they can carry more data. Fiber optic cables are less susceptible than metal cables to interference.
Fiber optic cables are much thinner and lighter than metal wires. Data can be transmitted digitally (the natural form for computer data) rather than analogically.
The main disadvantage of fiber optics is that the cables are expensive to install. In addition, they are more fragile than wire and are difficult to splice
Fiber Optic
A fiber-optic system is similar to the copper wire system that fiber-optics is replacing.
The difference is that fiber-optics use light pulses to transmit information down fiber lines instead of using electronic pulses to transmit information down copper lines
Transmitter is the place of origin for information coming on to fiber-optic lines.
Accepts coded electronic pulse information coming from copper wire.
Processes and translates information into equivalently coded light pulses.
A light-emitting diode (LED) or an injection-laser diode (ILD) can be used for generating the light pulses.
Fiber Optic
SPEED: Fiber optic networks operate at high speeds - up into the gigabits
BANDWIDTH: large carrying capacity DISTANCE: Signals can be transmitted further
without needing to be "refreshed" or strengthened.
RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or other nearby cables.
MAINTENANCE: Fiber optic cables costs much less to maintain.
Fiber Optic
Terrestrial microwave
Terrestrial microwave communication employs Earth-based transmitters and receivers.
The frequencies used are in the low-gigahertz range, which limits all communications to line-of-sight.
Microwave transmissions typically use a parabolic antenna that produces a narrow, highly directional signal.
A similar antenna at the receiving site is sensitive to signals only within a narrow focus.
Because the transmitter and receiver are highly focused, they must be adjusted carefully so that the transmitted signal is aligned with the receiver
Terrestrial microwave
A microwave link frequently is used to transmit signals in instances in which it would be impractical to run cables.
If you need to connect two networks separated by a public road, for example, you might find that regulations restrict you from running cables above or below the road. In such a case, a microwave link is an ideal solution.
Terrestrial microwave
Terrestrial microwave systems operate in the low-gigahertz range, typically at 4-6 GHz and 21-23 GHz, and costs are highly variable depending on requirements.
Long-distance microwave systems can be quite expensive but might be less costly than alternatives.
When line-of-sight transmission is possible, a microwave link is a one-time expense that can offer greater bandwidth than a leased circuit.
Terrestrial microwave
Satellite Microwave
wk10_Satellite___Microwave.ppt
DTE- Data Terminal Equipment
Data terminal equipment (DTE) is an end instrument that converts user information into signals or reconverts received signals.
A DTE device communicates with the data circuit-terminating equipment (DCE). The DTE/DCE classification was introduced by IBM.
A DTE is the functional unit of a data station that serves as a data source or a data sink and provides for the data communication control function to be performed in accordance with link protocol.
The data terminal equipment may be a single piece of equipment or an interconnected subsystem of multiple pieces of equipment that perform all the required functions necessary to permit users to communicate. A user interacts with the DTE (e.g. through a human-machine interface), or the DTE may be the user.
DCE – Data Circuit Terminating Eq
A Data circuit-terminating equipment (DCE) is a device that sits between the data terminal equipment (DTE) and a data transmission circuit.
It is also called data communications equipment and data carrier equipment.
Performs functions such as signal conversion, coding, and line clocking and may be a part of the DTE or intermediate equipment.
Interfacing equipment may be required to couple the data terminal equipment (DTE) into a transmission circuit or channel and from a transmission circuit or channel into the DTE.
Most commonly used with RS-232
DCE – Data Circuit Terminating Eq
The DCE includes timing elements for providing the DTE with any desired transmitter signal element timing and any desired receiver signal element timing.RS-232
The receiver signal element timing, the transmitter signal element timing, the transmit sampling clock pulsing the D/A converter and the receive sampling clock pulsing the A/D converter are all controlled by different sequences of digital values computed by the processing elements. By generating appropriate sequences of digital values, the processing elements can provide any desired relationship between the different clocks to satisfy a transmit signal element timing
QUIZ
1. Describe briefly the differences between DTE n DCE.
(4M)2. What is abbreviation of UTP stand for?
(2M)3. Describe 3 characteristics of Fiber
Optic (3M)4. What is Baud rate, Bit rate and
Bandwidth.(3M)
CHAPTER 4: NETWORK SYSTEM COMMUNICATION
4.1 ETHERNET Ethernet is the most widely-installed local area
network ( LAN) technology. Specified in a standard, IEEE 802.3, Ethernet was
originally developed by Xerox from an earlier specification called Alohanet (for the Palo Alto Research Center Aloha network) and then developed further by Xerox, DEC, and Intel.
An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires.
Ethernet is also used in wireless LANs. T The most commonly installed Ethernet systems are
called 10BASE-T and provide transmission speeds up to 10 Mbps. Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD ) protocol.
CHAPTER 4: NETWORK SYSTEM COMMUNICATION
The Preamble consists of seven bytes all of the form 10101010, and is used by the receiver to allow it to establish bit synchronisation (there is no clocking information on the Ether when nothing is being sent).
The Start frame delimiter is a single byte, 10101011, which is a frame flag, indicating the start of a frame.
The MAC addresses used in 802.3 are always 48 bits long, although older versions of Ethernet used 16 bits. Individual addresses have a most significant bit of 0, multicast addresses a most significant bit of 1. An address of 48 �1s� is a broadcast to all stations on the local network. An interesting feature is that individual addresses may be local or global, with, respectively, a second most significant bit of 0 or 1. Local addresses have no significance except on the local Ethernet installation, but global addresses are unique: every system with an Ethernet interface has a unique global address hardwired into that interface.
The Length/EtherType field indicates the number of bytes of data in the frame , and can be anything from 0 to 1500 bytes. Frames must be at least 64 bytes long, not including the preamble, so, if the data field is shorter than 46 bytes .
Finally the Checksum field uses a CRC-32 polynomial code
4.2 OSI PROTOCOL
Senibina ~ mendefinisikan elemen penting untuk komunikasi data di antara peranti.
Protokol ~ satu set undang-undang yang meliputi komunikasi data. Ia merupakan perjanjian di antara pihak yang berkomunikasi berkenaan bagaimana komunikasi data boleh dilakukan. Ia membenarkan sistem komputer yang berbeza berkomunikasi dengan baik dan mengawal bagaimana komputer bertukar maklumat melalui media rangkaian.
4.2 OSI PROTOCOL
• Ia merupakan “blueprint” untuk keseluruhan rangkaian, termasuklah falsafah rekabentuk dan struktur logikal di antara perkakasan rangkaian yang mempengaruhi bahan proses (throughput), penggunaan CPU (utilization), perolehan kos (cost recovery), kebolehpercayaan (reliability) dan keserasian (compatibility).
• Senibina rangkaian atau senibina komunikasi juga dikenali sebagai model rujukan
WHY USE PROTOCOL??
Format data
Hantar
mel
physical port
encription
addressi
ngMod dialog
Electrical voltage
switching
Signal
mana
hantar dulu
compression
Error control
Flow control
Berapa laju
hantar electrical voltage
• Terdapat terlalu banyak aspek yang terlibat dalam komunikasi rangkaian, dan banyak kepelbagaian pula.
• Oleh itu, ia perlu kerangka untuk melihat komponen2 secara sistematik.
•Senibina rangkaian @ model rujukan menempatkan komponen2 rangkaian yg terlibat dalam bentuk lapisan.•Setiap lapisan menakrifkan perkhidmatan bagi perisian atau perkakasan
Format data
Hantar
melphysical port
encription
addressi
ng
Mod dialog
Electrical voltage
switching
Signal
mana
hantar dulu
compression
Error
control
Flow control
Berapa laju
hantar electrical voltage
PhysicalData LinkNetworkTransportSessionPresentationAplikasi
CONCEPT OF OSI LAYER
• Mengurangkan kesulitan merekabentuk senibina komunikasi, kebanyakan rangkaian disusun sbg beberapa siri lapisan @ peringkat, di mana setiap satu dibangunkan di atasnya.
• Bilangan, nama, kandungan dan fungsi setiap lapisan berbeza dari satu rangkaian dgn rangkaian yg lain.
• Bagaimanapun, dalam semua rangkaian, matlamat setiap lapisan adalah menawarkan perkhidmatan kepada lapisan di atasnya.
Host 1
Layer 3
Layer 2
Layer 1
Layer 6
Layer 5
Layer 4
Kebanyakan rangkaian disusun dalam beberapa siri lapisan @ peringkat.
Setiap lapisan dibangunkan di atas lapisan bawahnya.
Bilangan lapisan berbeza di antara rangkaian.
Nama, fungsi dan kandungan setiap lapisan berbeza di antara rangkaian
Tujuan setiap lapisan adalah menawarkan Perkhidmatan kpd lapisan di atasnya.
OSI MODEL
• Dibangunkan oleh ISO yang meliputi semua aspek komunikasi rangkaian.
• Ia dinamakan Open System Interconnections (OSI) Reference Model kerana ia berhubung dengan sistem terbuka yang tidak berasaskan pembekal.
• Sistem terbuka (open system) ~ satu model yg membenarkan dua sistem berbeza berkomunikasi tanpa mengira bentuk senibina.
• Sistem tertutup (closed system) ~ protokol pembekal yg spesifik yg tidak membenarkan komunikasi di antara sistem yg tidak sama.
OSI MODEL
• Model OSI adalah rangka lapisan utk rekabentuk sistem rangkaian yg membenarkan komunikasi untuk semua jenis sistem komputer.
• Ia mengandungi skema komunikasi utk fungsi2 komunikasi yang disusun dalam tujuh (7) lapisan.
OSI MODEL
Model OSI dibangunkan ke atas 7 lapisan: Fizikal (Physical layer) ~ lapisan 1 Pautan data (Data link layer) ~ Lapisan 2 Rangkaian (Network layer) ~Lapisan 3 Pengangkutan (Transport layer ) ~ Lapisan 4 Sessi (Session layer) ~ Lapisan 5 Persembahan (Presentation layer) ~ Lapisan 6 Aplikasi (Application layer) ~ Lapisan 7
Please Do Not Touch Steve’s Pet Alligator Physical, Data Link, Network, Transport, Session, Presentation,
Application
OSI
Lapisan sokongan pengguna (5,6,7) Membenarkan operasi di antara sistem perisian yg
tidak sama. Lapisan pengangkutan (4)
Memastikan transmisi data yg boleh dipercayai dari satu titik-ke-titik.
(UPPER LAYER)
Lapisan sokongan rangkaian (1,2,3) Berhubung dgn aspek fizikal utk menggerakkan data
dari satu peranti ke peranti lain (cth: spesifikasi elektrikal, hubungan fizikal, pengalamatan fizikal)
(LOWER LAYER)
OSI
• Lapisan Fizikal• Penghantaran bit data melalui media• Menakrifkan spesifikasi mekanikal dan
elektrikal• Lapisan Pautan Data
• Menyusun bit dlm bentuk frame• Penghantaran nod-ke-nod
• Lapisan Rangkaian• Menggerakkan paket dari sumber ke destinasi• Menyediakan antara rangkaian (routing,
switching, addressing)
OSI
• Lapisan pengangkutan• Menyediakan penghantaran mesej yg dipercayai
dari penghujung-ke-penghujung dan pembetulan ralat.
• Provide reliable end-to-end message delivery and error recovery.
• Lapisan sesi• Memulakan, mengekalkan dan memutuskan
perhubungan.• Lapisan persembahan
• Menterjemahkan, menyulitkan dan memampatkan data
• Lapisan Aplikasi• Membenarkan capaian ke atas sumber2 rangkaian.
OSI
Lapisan 7: Aplikasi ~ menggunakan perkhidmatan pemindahan fail yg disediakan seperti FTAM, FTP untuk mencapai rangkaian.
Lapisan 7: Aplikasi~ Menerima fail dan bersedia untuk digunakan oleh pengguna.
Lapisan 6: Persembahan ~ data dr lapisan aplikasi di format/menterjemah data dan melakukan pengenkripan dan mampatan (jika ada).
Lapisan 6: Persembahan~ menformat data -bentuk yg boleh difahami oleh aplikasi -melakukan decryption dan decompression (jika ada)
Lapisan 5: Sesi ~ Apabila data diterima drp lapisan persembahan, ia akan membuka sesi dialog dgn terminal B bagaimana data akan dipindahkan.
Lapisan 5: Sesi~ mengesahkan bahawa data telah diterima dengan sempurna atau tidak
Lapisan 4: Pengangkutan ~ memecahkan data dalam bentuk segmen dan memasukkan nombor urutan dan diberikan kepada lapisan rangkaian.
Lapisan 4: Pengangkutan~ mengumpulkan segmen2 yang diterima untuk membentuk data unit serta memeriksa ralat.
Lapisan 3: Rangkaian <header>~ Alamat logikal ditambah dan ia menentukan laluan yang akan diambil untuk menghantar data ke terminal B.
Lapisan 3: Rangkaian~ Menentukan sama ada data yg diterima adalah untuknya.
Lapisan 2: Pautan Data~ Alamat fizikal pengirim dan penerima ditambah disertakan dengan trailer utk kawalan ralat.
Lapisan 2: Pautan data~ Menerima data drpd lapisan fizikal dan memeriksa ralat.
Lapisan 1: FizikalMenukarkan bit ke dalam bentuk isyarat supaya penghantaran melalui media fizikal dapat dilakukan.
Lapisan 1: Fizikal~ Menukarkan isyarat ke dalam bentuk bit data.
4.3 TCP/IP
TCP and IP were developed by a Department of Defense (DOD) research project to connect a number different networks designed by different vendors into a network of networks (the "Internet").
It was initially successful because it delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large number of client and server systems.
Several computers in a small department can use TCP/IP (along with other protocols) on a single LAN.
The IP component provides routing from the department to the enterprise network, then to regional networks, and finally to the global Internet.
On the battlefield a communications network will sustain damage, so the DOD designed TCP/IP to be robust and automatically recover from any node or phone line failure.
This design allows the construction of very large networks with less central management. However, because of the automatic recovery, network problems can go undiagnosed and uncorrected for long periods of time.
4.3 TCP/IP
IP - is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world.
TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received.
TCP/IP LAYER
INTERNET ADDRESS
An Internet Protocol (IP) address is a numerical identification (logical address ) that is assigned to devices participating in a computer network.
IP addresses are stored as binary numbers, they are usually displayed in human-readable notations, such as 208.77.188.166 (for IPv4), and 2001:db8:0:1234:0:567:1:1 (for IPv6).
The role of the IP address has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."
In the original Internet routing scheme developed in the 1970s, sites were assigned addresses from one of three classes: Class A, Class B and Class C.
The address classes differ in size and number. Class A addresses are the largest, but there are few of them. Class Cs are the smallest, but they are numerous. Classes D and E are also defined, but not used in normal operation.
Internet routing used to work like this: A router receiving an IP packet extracted its Destination Address, which was classified (literally) by examining its first one to four bits. Once the address's class had been determined, it was broken down into network and host bits. Routers ignored the host bits, and only needed to match the network bits to find a route to the network. Once a packet reached its target network, its host field was examined for final delivery.
Class A - 0nnnnnnn hhhhhhhh hhhhhhhh hhhhhhhh
First bit 0; 7 network bits; 24 host bits Initial byte: 0 - 127 126 Class As exist (0 and 127 are reserved) 16,777,214 hosts on each Class A
Class B - 10nnnnnn nnnnnnnn hhhhhhhh hhhhhhhh
First two bits 10; 14 network bits; 16 host bits
Initial byte: 128 - 191 16,384 Class Bs exist 65,532 hosts on each Class B
Class C - 110nnnnn nnnnnnnn nnnnnnnn hhhhhhhh
First three bits 110; 21 network bits; 8 host bits
Initial byte: 192 - 223 2,097,152 Class Cs exist 254 hosts on each Class C
Class D - 1110mmmm mmmmmmmm mmmmmmmm mmmmmmmm
First four bits 1110; 28 multicast address bits
Initial byte: 224 - 247 Class Ds are multicast addresses
CLASS FORMAT
SUBNET MASK
32-bit value Generally used to subdivide (subnet) a given IP
class network into smaller (sub)networks Netmask determines which portion of an IP
address is the network address and which is the host address An IP address bit is a network address bit if the
corresponding netmask bit is 1 An IP address bit is a host address bit if the
corresponding netmask bit is 0 "Natural netmask" has all netid bit locations = 1
and all hostid bit locations = 0(e.g., 255.0.0.0, 255.255.0.0, and 255.255.255.0 for class A, B, and C networks, respectively)
DNS – DOMAIN NAME SYSTEM The Domain Name System (DNS) is a hierarchical naming
system for computers, services, or any resource participating in the Internet.
It translates domain names meaningful to humans into the numerical (binary) identifiers associated with networking equipment for the purpose of locating and addressing these devices world-wide.
An often used analogy to explain the Domain Name System is that it serves as the "phone book" for the Internet by translating human-friendly computer hostnames into IP addresses. For example, www.example.com translates to 208.77.188.166.
The Domain Name System makes it possible to assign domain names to groups of Internet users in a meaningful way, independent of each user's physical location.
Internet domain names are easier to remember than IP addresses such as 208.77.188.166 (IPv4) or 2001:db8:1f70::999:de8:7648:6e8 (IPv6). People take advantage of this when they recite meaningful URLs and e-mail addresses without having to know how the machine will actually locate them
FTP – FILE TRANSFER PROTOCOL
File Transfer Protocol (FTP) is a network protocol used to transfer data from one computer to another through a network such as the Internet.
FTP is a file transfer protocol for exchanging and manipulating files over a TCP computer network. An FTP client may connect to an FTP server to manipulate files on that server.
The most common use for FTP is to download files from the Internet.
When downloading a file from the Internet you're actually transferring the file to your computer from another computer over the Internet. This is why the T (transfer) is in FTP. You may not know where the computer is that the file is coming from but you most likely know it's URL or Internet address.
HTTP??
HTTP, short for Hyper Text Transfer Protocol, is the protocol for transferring hypertext documents that makes the World Wide Web possible.
A standard web address (such as http://www.yahoo.com/) is called a URL; the prefix (http in the example) indicates its protocol.
In order to fetch a web page for you, your web browser must "talk" to a web server somewhere else. When web browsers talk to web servers, they speak a language known as HTTP, which stands for Hyper Text Transfer Protocol. This language is actually very simple and understandable and is not difficult for the human eye to follow.
HTTP
GET / HTTP/1.0 Host: www.boutell.com And the server replies: HTTP/1.0 200 OK Content-Type: text/html <head> <title>Welcome to
Boutell.Com, Inc.!</title> </head> <body> The rest of Boutell.Com's home page appears here </body>
HTTP LAGII..
The first line of the browser's request, GET / HTTP/1.0, indicates that the browser wants to see the home page of the site, and that the browser is using version 1.0 of the HTTP protocol.
The second line, Host: www.boutell.com, indicates the website that the browser is asking for. This is required because many websites may share the same IP address on the Internet and be hosted by a single computer. The Host: line was added a few years after the original release of HTTP 1.0 in order to accommodate this.
The first line of the server's reply, HTTP/1.0 200 OK, indicates that the server is also speaking version 1.0 of the HTTP protocol, and that the request was successful.
If the page the browser asked for did not exist, the response would read HTTP/1.0 404 Not Found.
The second line of the server's reply, Content-Type: text/html, tells the browser that the object it is about to receive is a web page. This is how the browser knows what to do with the response from the server. If this line were Content-Type: image/jpg, the browser would know to expect a PNG image file rather than a web page, and would display it accordingly.
POP – POST OFFICE PROTOCOL A simple protocol to connect, retrieve
and check the email. Define as RFC 1939. POP allows user to log in to account,
verify the user names and passwords, retrieve the new and old email, alerting the user of new coming message and etc.
POP – POST OFFICE PROTOCOL
The Purpose of POP, the Post Office Protocol If somebody sends you an email it usually cannot be delivered
directly to your computer. The message has to be stored somewhere, though. It has to be stored in a place where you can pick it up easily. Your ISP (Internet Service Provider) is online 24 hours on 7 days of the week and will do that job. It receives the message for you and keeps it until you download it.
Let's suppose your email address is [email protected]. As your ISP's mail server receives email from the internet it will look at each message and if it finds one addressed to [email protected] that message will be filed to a folder reserved for your mail.
This folder is where the message is kept until either you retrieve it or one of your ISP's administrators finds your account has been filled with spam and decides to delete all the mail in it (no, this won't happen but it can very well happen that you go past your limit of space available for incoming messages and cannot receive any more).
Now, POP, the Post Office Protocol (as defined in RFC 1939) is what allows you to retrieve mail from your ISP. This is also about all the Post Office Protocol is good for.
POP – POST OFFICE PROTOCOL
What the Post Office Protocol Allows You to Do Like it seems everything on the internet, mail retrieval
is a client-server application. The Post Office Protocol defines how your email client should talk to the POP server. The POP is a very simple protocol. Things that can be done via the POP include:
Retrieve mail from an ISP and delete it on the server. Retrieve mail from an ISP but not delete it on the
server. Ask whether new mail has arrived but not retrieve it. Peek at a few lines of a message to see whether it is
worth retrieving. If you leave all your mail on the server, it will pile up
there and eventually lead to a full mailbox. When your mailbox is full, nobody will be able to send you any email before you haven't cleaned up.
HOW POP WORKS?? The Post Office Protocol (POP) used to retrieve mail from a remote
server is a very simple protocol. It defines the basic functionality in a straight forward manner and is easy to implement. Of course, it is also easy to understand. Let's find out what happens behind the scenes when your email program fetches mail in a POP account. First, it needs to connect to the server.
Hi, It's Me Usually the POP server listens to port 110 for incoming connections.
Upon connection from a POP client (your email program) it will hopefully respond with +OK pop.philo.org ready or something similar. The +OK indicates that everything is — OK. Its negative equivalent is -ERR, which means something has gone wrong. Maybe your email client has already shown you one of these negative server replies.
Now that the server has greeted us, we need to log on using our username (let's suppose the user name is "platoon"; what the server says is printed in italics):
+OK pop.philo.org readyUSER platoon
HOW POP WORKS cont..
Since a user with this name does exist, the POP server responds with +OK . Were there no such user at the server, it would of course make us panic with -ERR user unknown.
To make the authentication complete we also need to give our password. This is done with the "pass" command:
+OK send your passwordpass noplato
If we type the password correctly, the server responds with +OK great password or whatever the programmer of the POP server had in mind. The important part again is the +OK. Unfortunately, passwords can also be wrong. The server notes this with a dry -ERR username and password don't match (as if you'd use your user name as your password).
If everything went okay, though, we are connected to the server and it knows who we are, thus we're ready to peek the newly arrived mail.
CHAPTER 5 :NETWORKING MEDIA
CHAPTER 5: NETWORKING MEDIA Copper media Optical media Wireless media
Electricity Basics The basic unit of all matter is an atom. Nucleus – center part of the atom
(protons and neutrons)
Protons – particles that have positive charge
Neutrons – particles that have no charge (neutral)
Electrons – particles that have negative charge and orbit the nucleus
Electricity Basics
Creating Stable Atoms Electrons in certain atoms can be pulled free
from the atom and made to flow – this is electricity (a free flow of electrons).
Static Electricity Loosened electrons that stay in one place,
without moving and with a negative charge. Can create electrostatic discharge, which can
create serious problems for computers.
Types of Electrical Materials
Insulators Electrons flow poorly Plastic, paper, rubber, dry wood, air, and glass
Conductors Electrons flow well Copper, silver, gold, solder, water with ions,
humans
Semiconductors Electrons flow can be controlled precisely Carbon, germanium, gallium arsenide, silicon
Measuring Electricity Voltage Resistance and impedance Current Alternating current Direct current Circuits Cable specification and termination
Current Flow
A 6-volt flashlight uses a simple circuit.
Electrical GroundsSurge suppressors, uninterruptible power supplies, and wall outlets all connect to a transformer and to the earth ground.
Copper Media
Cable Specifications
Cable Specifications
• 10BASE5 – speed of transmission at 10 Mbps– type of transmission is baseband– 5 represents the capability of the cable to allow the signal to
travel for approximately 500 meters before attenuation could disrupt the ability of the receiver to appropriately interpret the signal being received.
– often referred to as Thicknet
Cable Specifications
• 10BASE2 – speed of transmission at 10 Mbps– type of transmission is baseband– The 2, in 10BASE2, represents the capability of the cable to allow
the signal to travel for approximately 200 meters, before attenuation could disrupt the ability of the receiver to appropriately interpret the signal being received. 10BASE2 is often referred to as Thinnet.
Cable Specifications
• 10BASE-T – speed of transmission at 10 Mbps– type of transmission is baseband, or digitally interpreted– T stands for twisted pair
Coaxial Cable Coaxial cable consists
of a hollow outer cylindrical conductor that surrounds a single inner wire made of two conducting elements.
It can be run without as many boosts from repeaters, for longer distances between network nodes than either STP or UTP cable.
Coaxial Cable
Shielded Copper Cable Shielded twisted-pair cable (STP) combines the
techniques of shielding, cancellation, and twisting of wires.
Unshielded Twisted Pair Unshielded twisted-pair cable (UTP) is a four-
pair wire medium used in a variety of networks. Each of the 8 individual copper wires in the UTP cable is covered by insulating material.
Unshielded Twisted Pair (UTP)
Straight-through
Cross-over Rollover
www.cisco.com/warp/ public/701/14.html
Unshielded Twisted Pair (UTP)
• The cable that connects from the switch port to the computer NIC port is called a straight-through cable.
Host or Router
Hub or Switch
Unshielded Twisted Pair (UTP)
• The cable that connects from one switch port to another switch port is called a crossover cable.
Hub or Switch
Hub or Switch
Unshielded Twisted Pair (UTP)
• The cable that connects the RJ-45 adapter on the com port of the computer to the console port of the router or switch is called a rollover cable.
UTP Rollover Cable
Optical Media
Electromagnetic Spectrum
Electromagnetic Energy Radio Microwaves Radar Visible light X-rays Gamma rays
If all the types of electromagnetic waves are arranged in order from the longest wavelength down to the shortest wavelength, a continuum called the electromagnetic spectrum is created.
Ray Model of Light When electromagnetic waves travel out from a
source, they travel in straight lines called rays. Light travels at different slower speeds through
materials like air, water, and glass. When a light ray called the incident ray, crosses
the boundary from one material to another, some of the light energy in the ray will be reflected back.
Reflection When a ray of light (the
incident ray) strikes the shiny surface of a flat piece of glass, some of the light energy in the ray is reflected.
The angle between the incident ray and a line perpendicular to the surface of the glass at the point where the incident ray strikes the glass is called the angle of incidence.
Refraction When a light strikes the
interface between two transparent materials, the light divides into two parts.
Part of the light ray is reflected back into the first substance, with the angle of reflection equaling the angle of incidence.
The remaining energy in the light ray crosses the interface and enters into the second substance.
Total Internal Reflection
A light ray that is being turned on and off to send data (1s and 0s) into an optical fiber must stay inside the fiber until it reaches the far end.
Laws of Reflection
The following two conditions must be met for the light rays in a fiber to be reflected back into the fiber without any loss due to refraction: The core of the optical fiber has to have a
larger index of refraction than the material that surrounds it (the cladding).
The angle of incidence of the light ray is greater than the critical angle for the core and its cladding.
Laws of Reflection
Laws of Reflection
NA = sin Ø =21
22 nn
n = refraction index Ø = angle of light
Multimode Fiber If the diameter of the
core of the fiber is large enough so that there are many paths that light can take through the fiber, the fiber is called “multimode” fiber.
Single-mode fiber has a much smaller core that only allows light rays to travel along one mode inside the fiber.
Single-Mode Fiber
The major difference between multimode and single-mode fiber is that single-mode allows only one mode of light to propagate through the smaller, fiber-optic core.
Single-mode fiber is capable of higher rates of data transmission and greater cable run distances than multimode fiber.
Single-mode fiber can carry LAN data up to 3000 meters. Multimode is only capable of carrying up to 2000 meters.
Other Optical Components
Optical fiber links use light to send data. A transmitter is needed to convert the
electricity to light and at the other end of the fiber convert the light back to electricity.
Other Optical Components (cont.)
The semiconductor devices that are usually used as receivers with fiber-optic links are called p-intrinsic-n diodes (PIN photodiodes).
Connectors are attached to the fiber ends so that the fibers can be connected to the ports on the transmitter and receiver.
Signals and Noise in Optical Fibers
The farther a light signal travels through a fiber, the more the signal loses strength. This attenuation is due to several factors involving the nature of fiber itself. Scattering of light in a fiber is caused by microscopic non-
uniformity (distortions) in the fiber that reflects and scatters some of the light energy.
Absorption makes the light signal a little dimmer. Another factor that causes attenuation of the light signal is
manufacturing irregularities or roughness in the core-to-cladding boundary.
Graded index multimode fiber is designed to compensate for the different distances the various modes of light have to travel in the large diameter core.
Installation, Care, and Testing of Optical Fiber If the fiber is stretched
or curved too tightly, it can cause tiny cracks in the core that will scatter the light rays.
Bending the fiber in too tight a curve can change the incident angle of light rays striking the core-to-cladding boundary.
Installation, Care, and Testing of Optical Fiber (cont.) Interducting protects the
fiber, makes it easier to pull, and ensures that the bending radius (curve limit) of the fiber is not exceeded.
Two of the most important testing instruments are Optical Loss Meters and Optical Time Domain Reflectometers (OTDRs).
Wireless Media
WLAN Organizations and Standards
IEEE is the prime issuer of standards for wireless networks. The standards have been created within the framework of the
regulations created by the Federal Communications Commission (FCC).
802.11 standard is Direct Sequence Spread Spectrum (DSSS). DSSS applies to wireless devices operating within a 1 to 2 Mbps range.
802.11b may also be called Wi-Fi™ or high-speed wireless and refers to DSSS systems that operate at 1, 2, 5.5 and 11 Mbps. The majority of 802.11b devices still fail to match the 11 Mbps
throughput and generally function in the 2 to 4 Mbps range. 802.11a covers WLAN devices operating in the 5 GHZ
transmission band. 802.11a is capable of supplying data throughput of 54 Mbps and with
proprietary technology known as "rate doubling" has achieved 108 Mbps.
In production networks, a more standard rating is 20-26 Mbps. 802.11g provides the same throughout as 802.11a but with
backwards compatibility for 802.11b devices.
Wireless Devices and Topologies
An access point (AP) is commonly installed to act as a central hub for the WLAN "infrastructure mode".
The AP is hard wired to the cabled LAN to provide Internet access and connectivity to the wired network.
APs are equipped with antennae and provide wireless connectivity over a specified area referred to as a cell.
Most commonly, the range will be from 91.44 to 152.4 meters (300 to 500 feet).
Access Points To service larger areas,
multiple access points may be installed with a degree of overlap.
A 20-30% overlap is desirable.
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.
How WLANs Communicate
After establishing connectivity to the WLAN, a node will pass frames similarly to any other 802 network.
WLANs do not use a standard 802.3 frame.
WLANs use CSMA/CD When a source node
sends a packet, the receiving node returns a positive acknowledgment (ACK).
Authentication and Association IEEE 802.11 lists two types of
authentication processes. Open system – only the SSID must match Shared key – requires WEP (Wireless
Equivalency Protocol) encryption. Association permits a client to use the
services of the AP to transfer data.
Radio Wave and Microwave Spectrums
Computers send data signals electronically. Radio transmitters convert these electrical signals to radio waves.
Changing electric currents in the antenna of a transmitter generates the radio waves.
Signals and Noise on a WLAN The most obvious source of a signal
problem is the transmitting station and antenna type.
Leakage from a microwave of as little as one watt into the RF spectrum can cause major network disruption.
Fog or high moisture conditions can affect wireless networks.
Lightning can also charge the atmosphere and alter the path of a transmitted signal.
Wireless Security
VPN - Virtual Private Networking EAP-MD5 Challenge - Extensible
Authentication Protocol LEAP (Cisco) - Lightweight Extensible
Authentication Protocol User authentication Encryption Data authentication
FIBER OPTIC TERMINATION PROCESS
Precautions Always wear your safety glasses. Glass
fiber pieces are very sharp and dangerous Prevent epoxy/adhesive contact with skin
or eyes Promptly dispose glass fiber pieces into
fiber disposal bottle or on a loop of tape Never directly look into a fiber. The
invisible laser light can damage your eyes
FIBER OPTIC TERMINATION PROCESS
Components of a Corning’s field-installable SC connector (for 3mm jacketed cable)
Step 1: Fiber Cable Preparation
Slide the 3mm strain relief boot onto the cable end to be terminated
Per connector manufacturer’s instruction, use jacket
stripper (2.0mm hole) to remove fiber jacket to specified length and expose the aramid yarn. (the Kevlar)
Trim the aramid yarn to specified length with scissors according to the spec.
Fiber jacket and aramid yarn stripped to specified length per connector manufacturer’s spec
Step 1
Fiber Optic Cable Jacket Strippers
Aramid Yarn Cutter
Step 1
Fold the aramid yarn back and slide the crimp ring onto the cable, keep folding the aramid yarn back with the crimp ring.
Use a permanent marker to mark specified length from end of the jacket per manufacturer’s spec on fiber tight buffer.
Step 1
Strip the buffer in 5mm increments up to the mark with your preferred buffer and coating stripper.
Strip the buffer with a No-Nik 200um fiber stripper
Step 1
Clean the stripped fiber with a link-free wipe soaked in isopropyl alcohol and put it aside for later use. (Be careful not to contaminate the cleaned fiber!)
Step 2: Epoxy/Adhesive Preparation Here we use Tra-Con BAF253 Bipax package as
the epoxy sample, please follow your epoxy manufacturer’s epoxy preparation procedure.
Open the divider of the Bipax package, and roll the epoxy package on a flat surface with the epoxy mixer to mix the epoxy. When the epoxy changes to a consistent color throughout, the epoxy is ready.
Open the divider of the Bipax epoxy package. Use Epoxy mixer to mix the package.
Step 2
Remove the plunger from the 3-cc epoxy syringe, cut one corner of the Bipax epoxy package, and pour the epoxy into the syringe. Replace the plunger back into the syringe. Use an inexpensive regular scissors to cut the
package. DO NOT use the aramid yarn cutter! The aramid yarn cutter will be ruined if contaminated by epoxy.
Try not to trap air in the syringe when pouring the epoxy, air bubbles can cause voids during epoxy curing.
Pour into syringe - 3cc Epoxy Syringe
Hold syringe vertically with the needle up. Let the epoxy run to the bottom. Slowly move the plunger up, forcing out the air.
Wipe the epoxy that squirts out of the needle with a wipe.
Step 3: Inject Epoxy/Adhesive into Connector Ferrule
Take a connector, remove and throw away the cap from the rear of the assembly since you won’t need it any more.
Remove the dust cap from the connector ferrule (front of the assembly) and keep it. You will need it to protect the finished connector.
Hold the connector with ferrule pointed up; insert the syringe into the connector guiding tube until it stops in the connector.
Slowly push the plunger to inject epoxy into the connector body, stop once you see epoxy bead appears at the tip of the ferrule, and remove the syringe.
Step 4: Insert Fiber into Connector Slide the fiber into the connector all the
way back to the jacket. As you feed the fiber into the connector, rotate the connector back and forth so epoxy gets spread all around the fiber and keeps the fiber to the center of the hole in the ferrule.
Step 5: Crimp Connector
Slide the crimp ring back down the cable jacket, away from the connector, to free the aramid yarn. Use tweezers to spread the aramid yarn evenly around the back of the connector body.
Slide the crimp ring back towards the connector over the aramid yarn until it stops against the wall of the crimp body.
Place the connector assembly into your crimper tool hex, make sure the cable jacket is under the crimp ring, and squeeze the crimper tool’s handles shut to crimp the connector. Remove the connector from the crimper tool.
Slide 3mm strain relief boot over the crimp ring. The connector is now ready for next step.
HOW TO CONNECT P2P NETWORK
HOW TO ADD NIC/NETWORK ADAPTER
CONFIGURE THE TCP/IP PROTOCOLIP ADDRESS
Connect to A Workgroup
TAKE HOME TEST
CHAPTER II : PROTOCOLS A network protocol defines rules and conventions for communication
between network devices. a convention standard that controls or enables the connection,
communication, and data transfer between computing endpoints In its simplest form, a protocol can be defined as the rules governing the
syntax, semantics, and synchronization of communication. Protocols may be implemented by hardware, software, or a combination of the two. At the lowest level, a protocol defines the behaviour of a hardware connection.
Most of the Internet's communication protocols are described in the RFC(Request For Comment) data of the Internet Engineering Task Force (or IETF).
Protocols for computer networking all generally use packet switching techniques to send and receive messages in the form of packets.
Network protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received.
Some protocols also support message acknowledgement and data compression designed for reliable and/or high-performance network communication.
Hundreds of different computer network protocols have been developed each designed for specific purposes and environments.
Monolithic Protocol: a computer system architecture where processing, data and the user interface all reside on the same system
