I. Introduction to Networking...I. Introduction to Networking A computer network is a group of...

©2020 Gilbert Ndjatou

I. Introduction to Networking

➢ A computer network is a group of computer systems and other computing devices that are connected

by a physical communication medium such as:

• wire,

• radio wave, or

• light beam.

➢ Computer networks are primarily used to facilitate:

• communication and

• resource sharing among a wide range of computing devices.

➢ Examples of software applications that are used for communication are:

• Email

• Audio and voice telephone calls, and

• Video teleconferencing.

➢ Examples of resource that are shared are:

• Printers

• Hard drives

• Games, and

• Information such as files or web pages,

➢ Services are provided on a network by network application software.

➢ A network application software consists of two or more programs that run on different hosts and

communicate with one another over the network.


Packet Switching Networks

➢ In a packet switching network, multiple senders (computers) can transmit data over a shared network

communication medium.

➢ The data to be transmitted is subdivided into small blocks of consecutive bytes called packets

➢ A packet also includes the identification of the sender and the intended receiver of the packet in addition

of the data.

➢ The maximum size of a packet depends on the packet switching technology. But a common maximum

packet size is 1500 bytes.

➢ In the figure that follows, three computers are using the same network communication medium to send

data to three other computers.

Statistical Multiplexing

➢ A packet switching network uses statistical multiplexing to send the packets from multiple sources on

the same communication medium at the same time. That means:

• Packets from multiple sources are sent one after another on the same communication medium and,

• the system allows other senders to transmit some of their packets before the first sender can transmit

the next packet.


Characteristics of a Packet Switching Network

➢ A packet switching network has the following characteristics:

• Arbitrary, asynchronous communication:

− It allows a sender to communicate with more than one recipient.

− A given recipient can receive packets from more than one sender.

− The sender can generate and send packets at any time, and

− A sender can delay arbitrary long times between two packets.

• Connectionless communication service:

− The sender does not need to pre-establish a communication before it starts to send packets.

− It does not need to inform the network when a communication terminates.

• Performance varies due to statistical multiplexing among packets:

− A packet switching network is designed in such a way that each sender sharing a network has a

fair share of the communication medium.

− That means, if N senders have packets ready to send, a given sender should be able to transmit

1/N of all packets.

➢ Packet switching networks are classified according to the distance that they span as follows:

• Local Area Network (LAN)

• Metropolitan Area Network (MAN), and

• Wide Area Network (WAN)

➢ A local area network (LAN) is a computer network that interconnects computers within a limited area

such as a residence, school, laboratory, university campus or office building.

➢ Metropolitan Area Network (MAN) spans a major city

➢ Few MAN technologies have been created and MAN networks have not been commercially successful.

➢ A wide area network (WAN) covers a larger geographic distance, and also generally involves leased

telecommunication circuits or Internet links.

https://en.wikipedia.org/wiki/Leased_line

https://en.wikipedia.org/wiki/Leased_line

https://en.wikipedia.org/wiki/Internet


Network Technologies

➢ A network technology refers to the following:

• The way packets of data (a.k.a frames) are represented in that network, and

• The method a network interface uses to access the communication medium and to send data frames.

➢ The two major technologies used on Local Area Networks (LAN) are:

• The Ethernet that is commonly used in wired local area networks, and

• The Wi-Fi or WiFi which is the technology for wireless local area networking with devices based on

the IEEE 802.11 standards.

➢ The Ethernet was commercially introduced in 1980 and first standardized by IEEE in 1983 as IEEE

802.3.

➢ Professionals usually say that LANs connect computers, with the understanding that a device such as a

printer can also connect to a LAN.

➢ The most widely used standards for LANs have been created by the Project 802 LAN/WAN Standards

Committee of the Institute for Electrical and Electronics Engineers (IEEE).

➢ LAN standards are assigned the identifiers 802.1, 802.2, . . . etc.

➢ Devices that can use Wi-Fi technology include the following:

• personal computers,

• video-game consoles,

• smartphones,

• digital cameras,

• tablet computers,

• smart TVs,

• digital audio/video players and

• modern printers

➢ WANs use technologies designed to carry data over longer distances such as:

• Frame relay,

• SONET, and

• Asynchronous Transfer Mode (ATM)

https://en.wikipedia.org/wiki/IEEE_802.11

https://en.wikipedia.org/wiki/Smartphone

https://en.wikipedia.org/wiki/Tablet_computer

https://en.wikipedia.org/wiki/Smart_TV


Wired Local Area Network Components

➢ Network hardware and software are needed to connect a stand-alone computer to a LAN.

➢ To connect a stand-alone computer to wired LAN that uses the Ethernet technology, you need the

following network hardware:

• A Network Interface Controller (NIC)

• A Network medium, and

• An interconnecting device

Network Interface Controller (NIC) and Media Access

Control (MAC) Address

➢ A network interface controller (NIC), also known as network interface card, network adapter, LAN

adapter or physical network interface, is a computer hardware component that is built into a computer

motherboard or is plugged into a motherboard expansion slot.

➢ The following figure shows a PCIe x1 NIC.

Figure 8-14 A PCIe x1 NIC


➢ Every Network Interface Controller is assigned a unique 48-bit MAC (media access control) address

also referred to as Ethernet address.

➢ A NIC’s MAC address is stored in Read Only Memory (ROM) on the NIC.

➢ The standard (IEEE 802) format for printing a MAC address in human-friendly form is to subdivide it

into 6 consecutive groups of bytes (with each four bits of a byte translated into hexadecimal) separated

by hyphens.

Examples:

0010 0011 1011 0100 0101 0110 1000 0111 1010 0110 1001 0111

= 2 3 - B 4 - 5 6 - 8 7 - A 6 - 9 7

➢ The 48-bit MAC address is assigned to a NIC as follows:

• The left-most group of 3 bytes (24 bits) is assigned by IEEE and

• The right-most group of 3 bytes (24 bits) is assigned by the manufacturer and is used to identify a

particular NIC.

➢ The left-most 3 bytes (24 bits) of a MAC address is referred to as the Organizationally Unique

Identifier (OUI) and is used to identify the manufacturer of the NIC.

Examples:

MAC Address OUI NIC identification

01-23-45-67-89-AB 01-23-45 67-89-AB

48-2E-6C-1A-59-3D 48-2E-6C 1E-59-3D

➢ A NIC provides a connection between the computer and the network medium.

➢ It does the following:

• For outgoing messages, it does the following (Figure 2-11, Page 68):

− Receive packets from the network protocol

− Create frames by adding source and destination MAC addresses and the Cycle Redundancy

Check (CRC) data (for error checking and correction)

− Convert the frame data into signals in a format that is suitable for the network medium,

− Transmit the signals to the network medium


Figure 2-11, Page 68

• For incoming messages, it does the following (Figure 2-1-, Page 67):

− receive bit signals from the network medium and assembles them into frames,

− verify the frame’s destination MAC address, and ignore frames with destination MAC

addresses that does not match the NIC’s MAC address or is not FF:FF:FF:FF:FF:FF:FF:FF

(broadcasted frame)

− Perform the Cycle Redundancy Check (CRC) computation for error correction of the data

− remove the frame header and trailer

− transfer the packet to the network protocol

Figure 2-1-, Page 67


➢ A NIC typically has an 8P8C (8 position 8 contact) socket where the network cable is connected.

➢ A few LEDs on a NIC inform the user of whether the network is active, and whether or not data

transmission occurs.

➢ A NIC typically support speeds of 10 Mbit/s, 100 Mbit/s, and 1000 Mbit/s data transfer rate.

➢ Such NICs are designated as "10/100/1000", meaning that they can support a notional maximum transfer

rate of 10, 100 or 1000 Mbit/s.

➢ 10 Gigabit Ethernet NICs are also available, and, as of November 2014, are beginning to be available on

computer motherboards.

The Ethernet Frame Format

➢ As stated earlier, Ethernet is the most popular LAN technology.

➢ In addition to the MAC address of its NIC, a computer on an Ethernet LAN is also identified by its IP

(Internet Protocol) address.

➢ In addition to the data to be transmitted over a LAN, a packet that comes from the network protocol also

includes the IP address of the source computer and the IP address of the destination computer.

➢ An Ethernet frame length can vary from 64 bytes to 1518 bytes.

➢ It consists of the following:

• The destination MAC address 6 bytes

• The source MAC address 6 bytes

• The Ethernet frame type 2 bytes

• The payload (corresponds to the packet) 46 to 1500 bytes

• The Cycle Redundant Check (CRC) 4 bytes

➢ The payload consists of the following:

• The destination IP address

• The source IP address

• The data to be transmitted


➢ The header of an Ethernet frame consists of the following:

• The destination MAC address

• The source MAC address, and

• The Ethernet frame type.

➢ The Cycle Redundancy Check (CRC) is an error-correcting code that is designed to protect against

common types of errors on communication channels.

➢ The Ethernet frame type is also referred to as the EtherType.

➢ It is used by the sender to indicate which protocol is encapsulated in the payload of the frame (and

possibly the version of the IP address used in the payload:

➢ When the frame arrives at its destination, the receiver uses that code to determine which software module

should be used to process the frame.

Ethernet Error Handling

➢ Ethernet can detect whether a frame has been damaged in transit.

➢ The error checking code in an Ethernet frame is called Cycle Redundancy Check (CRC).

➢ This code is the result of a mathematical algorithm computed on the data in the frame.

➢ When a frame is received, this computation is repeated and if the result of the computation does not

match the CRC, it indicates that the data was altered during the transmission.

➢ A damaged frame is discarded. But the sending station is not informed of the error.

➢ The network protocol or the application sending the data is responsible for resending damaged or missing

data.


Wired LAN Interconnecting Devices

➢ Over the years, different sorts of devises have been used to connect devices on a LAN or to extend LANs

➢ Interconnecting devices used on wired LANs are

• Repeaters

• Hubs, and

• Switches

➢ The interconnecting device used on a wireless LAN is the wireless access point.

Network Repeaters

➢ In early networks, computers were connected in daisy-chain fashion by lengths of cable (Figure 2-1,

page 53), and

➢ There was a limit in the total length of the cabling and the number of computers that could be connected

because the signals become weaker as they go through the transmission medium farther from the source.

➢ This problem was solved by using repeaters.

Figure 2-1, page 53

➢ A repeater receives signals generated by a NIC, and then sends them (by repeating them) along to the

other parts of the network (Figure 2-2, page 53).

➢ A traditional repeater has two ports (or connections) that are used to extend the distance that a network

can cover.


Figure 2-2, page 53

Hubs and Network Bandwidth

➢ A hub is a device with at least four ports that was used on earlier networks to connect computers so that

signals can be sent from one NIC to all other NICs connected to the hub (Figure 2-3, page 54).

➢ A hub performs the following functions:

• Receive signals generated by a NIC connected to one of its ports

• Clean the signal by filtering out electrical noise

• Regenerate the signal to its full strength

• Transmit the generated signal to all other NICs connected to the hub.

Figure 2-3, page 54


➢ Two drawbacks of using a hub as a network connecting device follows:

• only one NIC can transmit data at a time,

• the data transmitted by one NIC is sent to all other NICs connected to the hub in addition to the

destination NIC.

➢ A network bandwidth is the amount of data that can be transferred on a network during a specific

interval.

➢ It is measured in bits per second

➢ Networks operate at speeds from 10 million bits per second (10 Mbps).

➢ A device bandwidth specifies how fast that device can send bits of data to the communication medium.

For example, a 10 Mbps hub transmits data at the rate of 10 million bits per second.

➢ The fact that two NICs connected to a hub cannot send signals at the same time is referred to as

bandwidth sharing.

➢ The effective bandwidth of a NIC is the actual speed at which it can transfer data over a network.

➢ On a LAN where n NICs are connected to a hub, the effect bandwidth of each of these NIC is the

bandwidth of the hub divided by n. For example, if 10 NICs are connected to a hub with a bandwidth of

10 Mbps, then the effective bandwidth of each of these NIC is 1 Mbps.

➢ Most hubs have indicator lights for:

• Power (when the switch power is turned on)

• link status (when a NIC is connected to a port)

• network activity, and (when data is being transmitted)

• collision (when two or more NICs want to send data at the same time)

➢ Because of their disadvantages, hubs are rarely used today: they are being replaced with switches.


Network Switches

➢ Like a hub, a switch is a device with ports that are used on networks to connect computers so that they

can communicate with one another. (Figure 2-5, page 57).

Figure 2-5, page 57

➢ Communication over a switched network is performed frame by frame.

➢ Unlike a hub that sends a signal that it receives from a NIC to all other NICs connected to its ports, a

switch actually receives a packet from a NIC, determines the port where the destination NIC is

connected, and forward the packet only to that NIC.

➢ A switch maintains a switching table to hold MAC addresses and their associated port numbers.

➢ The switching table that corresponds to the network in Figure 2.5 follows:

MAC Address Port Number

AA:A1 6

BB:B1 1

CC:C1 2

D:D1 3


➢ A switch does the following when it receives a frame:

• Read the source and the destination MAC addresses

• Look up the destination MAC address in the switching table

• Forward the frame to the port where the computer with that MAC address is connected

• Update the table with the source MAC address and its associated port number.

Notes:

• If the switch does not find the destination MAC address in the table, it forwards the frame to all ports.

• To ensure that the switching table does not become out of date, the following measures are taken:

− Each MAC address is entered in the table with a timestamp, and

− If a MAC address in the table is the source address of a frame, its time stamp is updated

− If a MAC address stays in the table beyond the maximum allowed time (usually 5 minutes) without

being updated, it is deleted.

Full and Half Duplex Modes of Operation

➢ In a switched network

− Two or more NICs connected to the switch can send frames at the same time, and

− A NIC can receive frames from two or more NICs connected to the switch

− A NIC can send a frame and receives another one at the same time: it is said to operate at full-

duplex mode.

− It means that the bandwidth of a device connected to a switched network is twice the bandwidth of

the switch.

➢ Hubs operate only at a half-duplex mode: a NIC connected to a hub can either send or receive a signal.

But it cannot perform both operations at the same time.

➢ The performance advantage of switches has made them the device of choice in networks of all sizes

➢ Like hubs, switches have indicator lights for:

o Power (when the switch power is turned on)

o link status (when a NIC is connected to a port)

o network activity, and (when data is being transmitted)

➢ Some switches also have lights to show whether a port is operating at full duplex or half duplex mode.


Wired LAN Extensions with Switches

➢ LANs are often extended by interconnecting switches to form a large LAN as in the following figure.

Figure 8-2

➢ Notice that the MAC addresses of the computers connected to Switch 2 are entered in the switching table

of Switch 1 with the port number where Switch 1 is connected to Switch 2.


Wired LAN Media

➢ A wired network medium is a cable that plugs into a computer NIC and makes the connection between

that computer and the rest of the network.

➢ In a network with two computers, the other end of the cable can just plug into the NIC of the second

computer and,

➢ In a network with three or more computers, the other end of the cable plugs into a port of an

interconnecting device.

➢ The two major characteristics of a wired network medium are:

• The bandwidth: The speed at which signals (electricity or light) travel through the medium, and

• The maximum distance that signals can effectively travel through the medium.

➢ The bandwidth is the number of bits per second that can be transmitted across a medium.

➢ A cable segment is the length of cable between two network devices such as a NIC and a switch.

➢ When signals travel through a cable, they begin to weaken past a point that a receiving station can read

them accurately.

➢ The maximum segment length of a transmission medium is the maximum length at which a receiving

station can read signals accurately.

➢ The following are the cables that are used on networks:

Coaxial Cable

➢ The coaxial cable is also called coax and was the predominant form of network cabling for years until

the early1990.

➢ Today, it is mostly used to connect a cable modem to the wall outlet that is installed by a cable

TV/Internet provider.


Twisted Pair Cable

➢ A twisted pair (TP) cable consists of one or more pairs of insulated strands of copper wire twisted

around one another and housed in an outer jacket or shield.

➢ There are two types of twisted pair cables: unshielded and shielded (Figure 4.1, page 148).

Figure 4.1, page 148

➢ Most networks use Unshielded Twisted Pair (UTP) cabling,

➢ Shielded Twisted Pair (STP) are mostly used only where electrical noise is a major problem.

➢ Unshielded Twisted Pair (UTP) cables are rated according to categories devised by the

Telecommunication Industry Association (TIA) and the Electronic Industries Alliance (EIA)

➢ The American National Standard Institute (ANSI) has also endorsed these standards now referred to as

the ANSI/TIA/EIA 568 Commercial Building Wiring Standard.

➢ The ANSI/TIA/EIA 568 standard includes eight categories for UTP wiring.

➢ These categories also govern the number of twists per foot or meter.


Categories of UTP Cables

Category 1: most UTP installed before 1982 fall in this category. It applies to traditional UTP phone

cabling designed to carry voice but not data.

Category 2: certifies UTP cabling for bandwidth up to 4 Mbps and consists of four twisted pairs of wire.


It remains in used in some older networks, but should be replaced when the network is upgraded.


It is the first ANSI/TIA/FIA designation that labels cables as datagrade (capable of carrying data) rather

than voice.


Category 5e: this category is an enhanced version of Category 5. It was designed to correct some

shortcomings in Cat 5 cabling. It certifies UTP cabling for up to 1 Gbps and the maximum cable length 100

meters = 328 ft.

Category 6: this standard was published in 2002 by the TIA/EIA and certifies UTP cabling for bandwidth

up to 1 Gbps and the maximum cable length 100 meters = 328 ft.

A UTP Path cable is short UTP cable that is used to connect a computer NIC to an RJ 45 jack or for

connecting a computer NIC or a patch panel port to a switch or a hub (Figure 4-4, page 152).

Figure 4-4 a UTP Patch cable


Fiber Optic Cable

➢ A fiber optic cable uses pulses of lights to represent bits.

➢ Fiber optic cables are highly secure: because they emit no external signals that might be detected, they

eliminate the possibility of electronic eavesdropping.

➢ A fiber optic cable is a good medium for long-distance data transmission because it has a lower

attenuation of the signals.

➢ Figure 4-18 shows a typical fiber-optic cable.

Figure 4-18 Fiber-optic cable

Characteristics of Fiber-Optic Cables

➢ The characteristics of a fiber-optic cable follow:

1. The maximum cable length is from 2 km (6562 ft) to 100 km (62.14 miles)

2. The bandwidth can be 10, 40, 100 Gbps and higher

3. The bend radius is 30 degree per foot

4. It is difficult to install and reroute, and is sensitive to strain and bending

5. It is not susceptible to eavesdropping

6. It is the most expensive of all cabling options

7. It is not susceptible to signal interference

8. It supports several types of connectors: the type of connector depends on the light emitting source

used to generate the light pulse and the corresponding light-detecting sensors used to detect them.


Types of Fiber-Optic Cables

➢ Fiber-optic cables come in two main types: Single mode fiber (SMF) and multimode fiber (MMF).

• Single mode fiber (SMF) cables cost more, are used in higher-bandwidth applications, and span the

longest distances with a maximum distance of 10 km.

• Multimode fiber (MMF) cables cost less but span shorter distances with a maximum distance of 2

km.

Use of Fiber-Optic Cables

➢ Fiber-optic cables are used as follows:

• For network backbone connections,

• For connections between hubs or switches,

• To connect wiring closets between floors or buildings.

• To span long distances between two wired network segments

• For network extension: When a computer is far from the switch or the hub

• It is also used by telecommunication providers and Internet service providers as the medium of

choice for long-distance telecommunications in which large amounts of voice and data traffic are

aggregated.

➢ You can also find fiber-optic patch cables that are used for connection from a fiber-optic patch panel to

a router or a switch.

➢ You need a pair of fiber modems to connect computers and wired LAN interconnected devices using a

fiber-optic cable.


➢ A fiber modem performs the following two tasks:

• It accepts electrical signals that come from the computer or the interconnected device and transforms

them into pulses of lights that are transmitted into the fiber-optic cable.

• It also accepts pulses of lights that come from the fiber-optic cable and transforms them into

electrical signals that are sent to the computer or the interconnected device.

Ethernet Standards with their Properties

➢ Ethernet can operate at different speeds over different types of media and

➢ Each variation is associated with an IEEE standard.

➢ Ethernet standards are generally expressed in one of the following two ways:

• By using the IEEE document number defining the standard. For example, IEEE 802.3.

• By using the XBaseY terminology where X is the speed of transmission, and Y is the length or type of

cabling. For example, with the standard 100BaseT, 100 specifies the speed of transmission (100

Mbps), and T specifies “twisted pair cabling.”

➢ The following table lists the major Ethernet standards with their properties. On this table,

• F indicates “fiber optic”

• L stands for “fiber optic with long wavelength”

• S stands for “fiber optic with short wavelength”

• C stands for “copper” jumper cables.


Hands-On Project 3-2 Determining and Changing your Ethernet Standard (page 63)

(Faculty – 15 minutes)

Description: To view your network connection properties to see at what speed your NIC is operating

Required Tools and Equipment:

- Two lab computers

- A switch

- Two patch cables

- The switch and the NICs must be able to connect at multiple speeds.


Twisted Pair Cable Plant Components

➢ In addition to the TP cables that are sold in spools of 1000 feet, a twisted pair cable plant also requires

the following components:

• RJ 45 connectors (also called RJ 45 plugs): are connectors to plug the cable into network

interfaces or other devices (Figure 4-3, page 151).

• Path cables: are short cables for connecting a computer NIC to an RJ 45 jack or for connecting a

computer NIC or a patch panel port to a switch or a hub (Figure 4-4, page 152).

• RJ 45 Jacks: are what you plug the RJ 45 connectors into when the computer is in a work area away

from hubs and switches (Figure 4-5, page 152).


• Patch panels: are used to terminate long run of cables from the work area (where computer are) to

the wiring closet. They can accommodate 12, 24, or 48 cables. (Figure 4-6, page 152).

• Distribution racks: are used to hold network equipment such as routers, switches, patch panels, and

rack mounted servers. They are mostly found in wiring closets and equipment rooms. (Figure 4-7,

page 153).


UTP Cable Plant Installation

➢ TIA/EIA developed the document “568 Commercial Building Wiring Standard” which specifies how

network media should be installed to maximize performance and efficiency.

➢ TIA/EIA 568 can be applied to any size network and divides the details of a cable plan into the following

six components:

Work Area (Figure 4-8, page 154)

• The work area is where workstations and other user devices are located.

• Faceplates and wall RJ 45 jacks are installed in the work area and

• Path cables connect computers and printers to wall jacks.

• Path cables in the work area should be limited to less than 6 meters (20 feet).

Horizontal Wiring (Figure 4-9, page 155)

• Horizontal wiring runs from the work area RJ 45 jack to the telecommunications closet.

• It is usually terminated at a patch panel.

• Wiring types include UTP cables Cat 5e or 6 or two fiber-optic cables.

• The maximum distance of a UTP cable should be 90 meters in order to allow up to 10 meters for the

patch cable that connects the patch panel to switch.


Telecommunications Closet (Figure 4-9, page 155)

• The telecommunication closet (TC) is used to house the switches that connect computer equipment in

the nearby work areas.

• The connection is provided by using the horizontal wiring.

• Typical equipment in a telecommunication closet includes the following:

− Patch panels (to terminate horizontal wiring runs),

− Switches (to provide network connectivity)

− Patch cables ( to connect patch panels to switches)

• In a larger installation, a telecommunication closet is connected to an equipment room by using a

backbone cable.

• In a small installation, a telecommunication closet

− also houses network servers, routers, and other major network equipment, and

− serves as the equipment room and the entrance facility.


Equipment Rooms (Figure 4-10, page 156)

• In a large installation, an equipment room is used to houses network servers, routers, switches, and

other major network equipment

• These equipment are connected to switches in telecommunication closets by using backbone cables.

• In a multi building installation, each building often has its own equipment closet.

Backbone Cabling (Figure 4-10, page 156)

• The Backbone cabling (a.k.a vertical cabling) is used to connect switches in telecommunication

rooms to other switches and/or routers in other telecommunication rooms and/or equipment rooms.

• This cabling runs between floors or wings of buildings and between buildings and are

− Fiber optic cables or

− UTP cables if the distance between rooms is less than 90 meters.

• Multimode fiber optic cables can extend up to 2000 meters, whereas single mode fiber optic cables

can reach distances up to 3000 meters.


Entrance Facilities

• An entrance facility (a.k.a demarcation point) is the location that holds the equipment that connect

an organization LAN to a third-party telecommunications provider.

• This facility can also serve as an equipment room.

Straight versus Crossover Cable

• There are two types of UTP cables:

− Straight-through cables, and

− Cross-over cables.

• In a straight-through cable, wires are connected to the same pins in the RJ 45 jack or plug at both

end of the cable (pin 1 connected to pin 1, pin 2 connected to pin 2, etc.). Examples of straight-

through cables are patch cables.

• In a cross-over cable, two wires are connected to opposite pins in the RJ 45 jack or plug at both end

of the cable.

• A straight through cable is often needed when you connect two devices of different types such as a

PC to a switch or a PC to a hub, and

• A cross-over cable is often needed when you connect two devices of the same type such as a hub to a

hub, a switch to a switch, a hub to a switch, or a PC to a PC.

• Auto-sensing devices are devices that you can connect to each other without the need of a cross-over

cable.

Rollover Cable

• A rollover cable or console cable is a cable designed to connect a PC serial communication port to a

Cisco device console port for configuring the Cisco device.

• You use a terminal emulation software such as PuTTY to get a command line interface prompt from

the Cisco device so that you can enter commands to view and change its configuration.


Hands-On Project 1-2 Upgrading a Stand-alone Computer to a Network Computer (page 14)

(Faculty – 10 minutes)

Objective: To connect a NIC to an interconnecting device with a patch cable.


- A lab computer

- A switch

- a patch cable


Network Software

➢ A computer must also have the necessary software to interact with the network hardware and to

communicate with other computers on a network.

➢ The Network software transforms a stand-alone operating system into a network operating system.

➢ Network software can be divided into the following categories:

• NIC drivers

• Network clients and servers, and

• Protocols.

NIC Drivers

➢ A NIC driver is a program that an operating system uses to send and receive messages to a NIC.

➢ Every NIC card installed in a computer must have an associated device driver installed in the operating

system.

➢ The device driver software manages the details of communicating with the NIC hardware in order to

send and receive data to and from the network media.

➢ Most operating systems are shipped with drivers for a wide range of NIC manufacturers and models.

➢ In Windows, each NIC is assigned a connection name as follows:

• Ethernet0 is assigned to the first NIC

• Ethernet1 is assigned to the second NIC if it is present, and so forth.

➢ But you can change a name to one that is more descriptive.

➢ You view a NIC setting in Windows 10 as follows:

• Right Click the Start and then click Network Connections

• Click Ethernet

• Click Change Adapter Options (the Network Connection windows that contains all the NICs and

Wireless NICs installed on the computer is displayed)

• Right click a NIC and then click Properties to open the dialog box shown in Figure 2.13.

− The “Connect Using” text box shows the type of NIC that is installed

➢ To change the NIC settings and its driver, click the Configure button.


Figure 2.13

Network Clients and Servers

➢ A network client software is a software that executes on a computer and requests information that is

stored on another computer or a device on a network.

➢ A network server software is a software that responds to requests for network resources from client

software running on other computers.

Examples: web servers, FTP servers, email servers, and Telnet server.

➢ Network client software can be an integral part of a well-known application such as a web browser or an

email client such as Microsoft Outlook.

Example: A web browser sends a request for a web document to a web server.

➢ They can also run in the background and enable programs without built-in client software to access

shared network resources on other computers.

Example: Client for Microsoft Network is installed in Microsoft Windows and allows programs such as

word processing programs to open files shared on another Windows computer or to print on a printer

attached to another Windows computer.


Protocols

➢ Network protocols define the rules for interactions between computers on a network.

That means the rules and formats that a computer must use when sending information across a network.

➢ When network client software and server software need to send a message on a network, they must pass

that message to the network protocols.

➢ The network protocols package the message in a format suitable for the network and send it to the NIC

driver.

➢ TCP/IP (Transfer Control Protocol/ Internet protocol) is the protocol suite used on most networks today.

Notes:

➢ A computer that hosts a network client software is in general referred to as the client computer, and

➢ A computer that hosts a network server software is in general referred to as server computer.


Network Communication on a LAN

➢ The steps of network communications follow:

A. On the client computer:

1. An application tries to access a network resource by attempting to send a message to another

application.

2. The network client software (integrated into the application or a standalone program)

a. detects the attempt to access the network

b. format the message generated by the application, and

c. pass the message on to the network protocol

3. The protocol does the following:

a. Package the message in a format suitable for the network, add the frame type to it, and

b. Send the message to the NIC driver

4. The NIC driver does the following

a. Add the MAC addresses of the source and the destination computers and the CRC to the packet

b. sends the frame (packet) to the NIC card which converts it into the necessary signals that are

transmitted across the network medium.

B. On the server computer:

1. The NIC on the server does the following:

a. Receive the signals from the network medium and

b. Convert the signals into message data which is read by the NIC driver

2. The NIC driver does the following:

a. Verify that the destination MAC address identifies the NIC as an intended recipient of the frame.

b. Remove the MAC addresses of the source and destination computers and the CRC from the frame

c. Use the CRC to make sure that there was no error in the transmission of the frame

d. Send the packet to the network protocol

3. The network protocol does the following:

a. Uses the frame type to determine which server software the message is being sent to

b. Pass the message to the destination server software.

4. The server software receives the message and responds by sending the requested data to the client

software using the four steps in Part A.


Note:

➢ Ethernet is considered a best-effort delivery system: when a frame is sent, there is no acknowledgement

or verification that the frame arrived at its intended destination.

➢ Ethernet relies on network protocols, such as TCP/IP to ensure reliable delivery of data.

Unicast, Broadcast, and Multicast MAC Addresses

➢ The IEEE addressing scheme supports three types of MAC addresses:

• Unicast MAC addresses,

• Broadcast MAC addresses, and

• Multicast MAC addresses.

Unicast MAC Address

➢ A unicast MAC address is the MAC address assigned to the NIC of a computer.

➢ A frame with a unicast MAC address as the destination address is delivered only to the computer with

that MAC address.

Broadcast MAC Address

➢ The broadcast MAC address is the MAC address FF:FF:FF:FF:FF:FF (with all 1’s).

➢ A frame with the broadcast MAC address as the destination address is delivered to all computers on the

LAN.

Multicast MAC Address

➢ All multicast MAC addresses have the OUI 01:00:5E.

➢ A multicast MAC address is used to identify a group of computers on a LAN.

➢ A frame with a multicast MAC address as the destination address is delivered to all the computers in the

group identified by that multicast MAC address.

➢ As an example of a situation where a multicast MAC addressing is needed, consider a computer lab

where all computer must all have the same application. One computer can be configured with all the

applications which will then be transferred from a server to all other computers using multicast frames.


Virtual Local Area Networks

➢ A switch that supports virtual local area networks (VLANs) allows you to configure its ports into

separate broadcast domains.

➢ That means, ports are grouped in such a way that a frame broadcast to one group can only be sent to

computers connected to those ports.

➢ Each such group of ports is referred to as a virtual area network (VLAN) and a router is needed for

communication between computers on different VLANs as shown in the following figure:

Figure 8.4

➢ VLANs make it possible for network administrators to group users and resources logically instead of by

physical location.

➢ A VLAN can also consists of ports on two or more switches as shown on the following figure.

Figure 8-5


Hands-On Project 1-3 Viewing Network Software Layers (page 20) (Students – 10 minutes)

Objective: To view the properties of a computer network connection and identify the layers of the network

communication process.

Required Tools and Equipment: virtual machine with Windows 10 operating system

Hands-On Project 1-4 Using ipconfig, ping, and arp (page 21) (Students – 15 minutes)

Objective: To use ipconfig, ping, and arp to view and test network addresses and connectivity

Required Tools and Equipment: virtual machine with Windows 10 operating system

Hands-On Project 2-2 Using Wireshark with a switch (page 61) (Faculty – 20 minutes)

Objective: To use the Wireshark protocol analyzer on a computer connected to other computers via a switch

to see that all data are note repeated to all stations


- 3 lab computers

- A switch

- 3 patch cables

Software: Wireshark

Hands-On Project 2-3 Examining a switch indicator lights and Uplink Ports (page 63)

(Faculty –15 minutes)

Objective: To examine the indicator lights of a switch and understand the purpose of the uplink port


- 3 lab computers

- 2 switches

- 1 crossover cable

- 4 patch cables

Software:

Hands-On Project 3-3 Viewing an Ethernet Frame (page 119) (Faculty – Lab computer, 30 minutes)

Objective: To examine the indicator lights of a switch and understand the purpose of the uplink port


- 3 lab computers

- 2 switches

- 1 crossover cable

- 4 patch cables

Software:


Wireless Networking

➢ These days, wireless networks are widely used on college and corporate campuses and in many public

locations such as airports, train and bus stations, and libraries in the form of hotspots.

➢ Many home and office users are now using wireless networks so that their computers are no longer

connected to a network cable.

➢ These computers are wirelessly connected to an Access Point or a router which connects to the Internet

via a wired connection to a cable modem or a similar device.

➢ Wireless networks are often used with wired networks to interconnect geographically dispersed LANs or

groups of mobile users with wired servers and resources on a wired LAN.

➢ The following figure shows a typical home wireless network.


Wireless Benefits

➢ Wireless networking offers the following capabilities:

• Creates temporary connections to wired networks

• Establishes backup or contingency connectivity for existing wired networks

• Extends a network’s span beyond the reach of wire-based or fiber-optic cabling, especially in older

buildings where rewiring might be too expensive

• Allows businesses to provide customers with wireless networking easily, offering a service that gets

customers in and keeps them there

• Enables users to roam around a corporate or college campus with their machines.

Types of Wireless Networks

➢ Wireless networks are subdivided into categories based on the role wireless components play in a

network.

➢ The following are the different categories:

▪ Local area networks (LANs)

− In a wireless LAN, components are used to provide connectivity for mobile users or across areas

that couldn’t otherwise be networked.

Example: older buildings where installing wiring is impractical.

▪ Extended LANs

– A wireless component is used to increase a LAN’s span beyond normal distance limitations for

wired-based or fiber-optic cables.

Example: connecting a point of sale to a LAN.

▪ Internet service

− Wireless technology is used to bring Internet access to homes and businesses because the Internet

Service Provider does not have the media infrastructure to do it.

▪ Mobile computing

– with mobile computing, users communicate by using a wireless networking medium such as a radio

or a cell phone frequency that enable them to move while remaining connected to a network.


Wireless Local Area Networks (WLANs)

➢ To connect a stand-alone computer to a wireless LAN, you need the following network hardware:

• A Wireless Network Interface Controller (WNIC), and

• A Wireless Access Point (WAP)

Wireless Network Interface Controller (WNIC)

➢ A wireless network interface controller (WNIC) is built into the motherboard of a laptop and portable

computers.

➢ You may also use a wireless network interface device with a USB interface and internal antenna on

communication devices that do not come with a WNIC.

➢ The combination of computer and a wireless network interface controller is called a station.

➢ A wireless network interface controller (WNIC) is a network interface controller that connects a

station to a wireless radio-based computer network.

➢ This card uses an antenna to communicate via microwave radiation through a wireless access point

(AP).

➢ Wireless NIC must be chosen according to the type of wireless AP you have installed.

➢ Wireless networking standards are specified as 802.11a, 802.11b, 802.11g, 802.11n, or 802.11ac.

➢ These standards are also specified as Wireless-a, Wireless-b, Wireless-g, Wireless-n, and Wireless-ac.

➢ These standards support increasing speeds and features in this order from slowest to the fastest: b, g, a,

n and ac.

➢ Wireless-b is among the earliest standards and supports speeds up to 11 Mbps transfer rate.

➢ Wireless-a and Wireless-g came next and support speeds up to 54 Mbps transfer rate.

➢ Wireless-n supports speeds from 54 Mbps to more than 600 Mbps.

➢ Newer standard Wireless-ac supports speeds faster than 1 Gbps and will eventually support almost 7

Gbps.

https://en.wikipedia.org/wiki/Wireless

https://en.wikipedia.org/wiki/Radio

https://en.wikipedia.org/wiki/Antenna_(radio)

https://en.wikipedia.org/wiki/Microwaves

https://en.wikipedia.org/wiki/Radiation

https://en.wikipedia.org/wiki/File:USB-wireless-adapter.jpg


Connecting a Station to a Wireless Network

➢ Figure 2-14 shows the Network & Internet control panel in Windows 10.

➢ This control panel lists all wireless APs in the range of your wireless NIC.

➢ The name assigned to a wireless network is called the service set identifier (SSID) and is configured on

the AP.

➢ You can click the network ID and then click the Connect button to connect to a wireless.

➢ You might also be prompted for a security key or a username and a password, depending on the network

security configuration.

➢ You also have the option to connect automatically whenever the network is in range of your computer.

➢ After you connect to a wireless network, you will see the Set Network Location window.

➢ The network location can be:

• Home

• Work, or

• Public

➢ It is used to set up the firewall rules for the connection.


Wireless Access Points

➢ A wireless access point (AP) is like a hub in that all computers on a wireless network send signals

through it to communicate with other computers.

➢ Most small business and home networks with wireless networks use a device called a wireless router that

combines the functions of an AP, a switch, and a router (Figure 2-9)

➢ Wireless routers are identified by two or more antennae on the device

➢ These routers are usually used with a cable or a DSL modem to provide access to the Internet

➢ Large businesses use dedicated APs to give wireless access to the corporate network as well as the

Internet.

➢ APs typically have one or more connectors for connection to a wired Ethernet network and

➢ Wireless networks are almost always connected to a wired network.

➢ All communications over a wireless network goes through the AP, which then retransmits or repeats the

signal to all other stations.

➢ Communication between two stations requires an extra step: The destination station sends an

acknowledgement back to the sending station to indicate that the frame was received.

➢ Because of the extra data transmissions in a wireless network, the effective bandwidth (the bandwidth

used for the actual data transmission) is about half of the physical bandwidth.

➢ An AP also shares its bandwidth with all stations in the wireless network: for example, if an AP operates

at 11 Mbps and is used on a wireless network with 11 stations, its effective bandwidth will be 5.5 Mbps

and each station will have .5 Mbps (500 Kbps) of effective bandwidth.


Hands-On Project 2-4 Connecting to a Wireless Access Point (page 72)

(Faculty – Lab computer, 15 minutes)

Objective: To connect to an access point


- 2 lab computers with WNICs

- 1 wireless AP

Software:

Review Exercises

Chapter 1: Pages 46 – 48: 11, 12, 13, 14, 17, 23

Chapter2: Pages 85 – 88: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 18

Chapter 3: Pages 136 – 138: 9, 10, 12, 16, 18, 20

Chapter 4: Pages 180 – 183: 1, 3, 5, 8, 9, 11, 12, 16, 19, 20, 23

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