Chapter 4 Network Access
The physical layer must generate the electrical, optical, or wireless signals that represent the __ and __ on the media.
"1" and "0"
A physical connection can be a _____ connection using a cable or a _______ connection using radio waves
Wired connection or wireless connection
Media that uses patterns of microwaves to represent bits.
Wireless
The signals are patterns of microwave transmissions
Wireless
To offer wireless capability, devices on a wireless network must be connected to what?
Wireless Access Point (AP)
Although UTP cable has essentially replaced coaxial cable in modern Ethernet installations, the coaxial cable design is used in:
Wireless Installation Cable internet installations
Coaxial cables attach antennas to wireless devices. The coaxial cable carries radio frequency (RF) energy between the antennas and the radio equipment.
Wireless Installations
What does WLAN NIC stand for?
Wireless Local Area Network Network Interface Card
he result of undesirable voltages and currents can include damage to?
network devices and connected computers, or injury to personnel.
What are the four different types of coax cable connectors?
BNC N type F type
The capacity of a medium to carry data.
Bandwidth
What is bandwidth?
Bandwidth is the capacity of a medium to carry data. Digital bandwidth measures the amount of data that can flow from one place to another in a given amount of time.
b/s
Bits per second
Cable service providers provide Internet connectivity to their customers by replacing portions of the coaxial cable and supporting amplification elements with fiber-optic cable. However, the wiring inside the customer's premises is still coax cable.
Cable Internet Installations
Attaches antennas to wireless devices-can be bundled with fiber-optic cabling for two-wat data transmission
Coaxial
Encoding or line encoding is a method of what?
Converting a stream of data bits into a predefined cod.
Media that uses electrical pulses to represents bit.
Copper
The signals are patterns of electrical pulses
Copper cable
There are three basic forms of network media. The physical layer produces the representation and groupings of bits for each type of media as:
Copper cable Fiber-Optic-cable Wireless
Electrical hazards are a potential problem because of copper wires. Why is this the case?
Copper wires can conduct electricity in undesirable ways. This could subject personnel and equipment to a range of electrical hazards. For example, a defective network device could conduct currents to the chassis of other network devices.
Is a disturbance caused by the electric or magnetic fields of a signal on one wire to the signal in an adjacent wire. In telephone circuits, it can result in hearing part of another conversation from an adjacent circuit. Specifically, when an electrical current flows through a wire, it creates a small, circular magnetic field around the wire, which can be picked up by and adjacent wire.
Crosstalk
Shielded twisted pair to what two forms of interference?
EMI and RFI Crosstalk
In LANS, UTP cables have color coded plastic insulation that do what?
Electrically isolates wires form each other and identifies each pair
EMI and RFI signals can distort and corrupt the data signals being carries by copper media. Potential sources of EMI and RFI include radio waves and electromagnetic device, such as fluorescent lights or electric motors.
Electromagnetic Interference (EMI) or Radio frequency Interference (RFI)
The timing and voltage values of the electrical pulses are also susceptible to interference from two sources:
Electromagnetic interference (EMI) or radio frequency interference (RFI) Crosstalk
What is encoding?
Encoding is the method or pattern used to represent digital information. Similar to ho Morse code encodes a message using a series of dots and dashes.
True or False: Bandwidth is speed that bits travel
False Bandwidth is sometimes thought of as the speed that bits travel, however this is not accurate. For example, in both 10Mb/s and 100Mb/s Ethernet, the bits are sent at the speed of electricity. The difference is the number of bits that are transmitted per second.
Media that uses patterns of light to represents bits.
Fiber-optic
The signals are patterns of light
Fiber-optic-cable
All three types of copper media are susceptible to what?
Fire and electrical hazards
Fire hazards exist because cable insulation and sheaths may be what?
Flammable or produce toxic fumes when heated or burned
List the different parts that make up a STP cable
Jacket Braided or Foil Shield Foil Shield Twisted-Pair
kb/s
Kilobits per second
Latency refers to what?
Latency refers to the amount of time, to include delays, for data to travel from one given point to another.
What is the drawback of using copper media?
Limited by distance Signal Interference
Mb/s
Megabits per second
What is modulation?
Modulation is the process by which the characteristic of one wave (the signal) modifies another wave (the carrier).
What does NIC stand for?
Network Interface Card
The physical layer standards address three functional areas:
Physical Components Encoding Signaling
In LANS, UTP cables have outer jackets that do what?
Protects the copper wire form physical damage
In LANS, UTP cables have twisted-pair wires that do what?
Protects the signal form interference and crosstalk
UTP cabling is terminated with what connector?
RJ-45
What connector is widely used in LANs with one type of media and in some WANs with another media type?
RJ-45
With wireless devices, data is transmitted using what?
Radio Waves
Counters EMI and RFI by using shielding techniques and special connectors
STP Shielded Twisted Pairs
The susceptibility of copper cables to electronic noise can also be limited by:
Selecting the cable type or category most suited to a given networking environment. Designing a cable infrastructure to avoid known and potential sources of interference in the building structure. Using cabling techniques that include the proper handling and termination of the cables.
What are the advantages and disadvantages between Shielded twisted-pair (STP) and Unshielded Twisted Pair (UTP) cabling?
Shielded twisted-pair provides better noise protection than UTP cabling. However, compared to UTP cable, STP cable is significantly more expensive and difficult to install. Like UTP cable, STP uses an RJ-45 connector
The longer a signal travels through copper, the more deteriorates. This is referred to as what?
Signal attenuation Note: For this reason, all copper media must follow strict distance limitations as specified by the guiding standards.
Tb/s
Terabits per second
To gain the full benefit of the shielding, STP cables are terminated with what?
Terminated with special shielded STP data connectors.
Due to a number of factors, throughput usually does not match the specified bandwidth in physical layer implementations. Many factors influence throughput, including:
The amount of traffic The type of traffic The latency created by the number of network devices encountered between source and destination.
What happens when the destination node physical layer receives encoded data from the source node?
The destination node physical layer retrieves these individual signals from the media, restores them to their bit representation, and passes the bits up to the data link layer as a complete frame
What does it mean if a hardware component is specified in standards associated with the physical layer?
The hardware is created to function by using the physical layer standards
The services and protocols in the TCP/IP suite are defined by who?
The internet Engineering Task Force (IETF)
What happens to a wireless as more wireless devices access it simultaneously?
The network performance slows down as more and more devices connect to the the wireless AP
In the physical layer what are considered physical components?
The physical components are the electronic hardware devices, media, and other connectors that transmit and carry the signals to represent the bits.
How does the physical layer prepare data link layer frames for transportation over the medium?
The physical layer encodes the frames and creates the electrical, optical, or radio waves signals that represent the bits in each frame
What are some factors that determine the practical bandwidth of a network?
The properties of the physical media The technologies chosen for signaling and detecting network signals Physical media properties, current technologies, and the laws of physics all play a role in determining the available bandwidth.
What are some of the cabling practices that are used to prevent potential and electrical hazards?
The separation of data and electrical power cabling must comply with safety codes Cables must be connected correctly Equipment must be grounded correctly Installations must be inspected for damage
If a STP cable is improperly grounded what can happen?
The shield may act as an antenna and pick up unwanted signals.
The method of representing the bits is called what?
The signaling method
The nature of the actual signals representing the bits on the media will depend on
The signaling method used
As data is moving down the OSI model what happens to it as it gets to the data link layer?
The user data is segmented by the transport layer, placed into packets by the network layer, and further encapsulated into frames by the data link layer
After the data link frames are encoded by the physical layer what does the physical layer do with the encoded data?
These signals are then sent on the media, one at a time
How does the physical layer standards define what type of signal represents a "1" and "0"?
This can be as simple as a change in the level of an electrical signal or optical pulse. For example, a long pulse might represent a 1 whereas a short pulse represents a 0. This is similar to the signaling method used in Morse code, which may use a series of on-off tones, lights, or clicks to send text over telephone wires or between ships at sea. There are many ways to transmit signals. A common method to send data is using modulation techniques. Modulation is the process by which the characteristic of one wave (the signal) modifies another wave (the carrier). .
A measure of the transfer of bits across the media
Throughput
What is throughput?
Throughput is the measure of the transfer of bits across the media over a given period of time.
True or Fales: All wireless devices must share access to the airwaves connecting to the wireless access point.
True
True or False: A detector in the network interface of a destination device must receive a signal that can be successfully decoded to match the signal sent.
True
True or False: Additionally, network cabling could present undesirable voltage levels when used to connect devices that have power sources with different ground potentials. Such situations are possible when copper cabling is used to connect networks in different buildings or on separate floors that use disparate power facilities. Finally, copper cabling may conduct voltages caused by lightning strikes to network devices.
True
True or False: TCP/IP standards are implemented in software and governed by the IETF.
True
Ture or False: In an internetwork or network with multiple segments, throughput cannot be faster than the slowest link in the path from source to destination.
True Even if all or most of the segments have high bandwidth, it will only take one segment in the path with low throughput to create a bottleneck to the throughput of the entire network.
Standards for copper media are defined for the:
Type of copper cabling used Bandwidth of the communication Type of connectors used Pinout and color codes of connections to the media Maximum distance of the media
Most common network media
UTP Unshielded Twisted Pairs
What are the tree main types of copper media used in networking?
Unshielded Twisted-Pair (UTP) Shielded Twisted-Pair (STP) Coaxial
What is the most common networking media?
Unshielded twisted-pair (UTP)
What are Ethernet NICs are used for what?
Used for a wired connection to the network
What is a WLAN NIC used for?
Used for connecting to a network wirelessly
What are NICs used for?
Used to connect a device to the network
A gigabit is how many bits?
1 Gb/s=1,000,000,000 bps
A megabit is how many bits?
1 Mb/s=1,000,000 bps
A terabit is how many bits?
1 Tb/s=1,000,000,000,000 bps
A kilobit is how many bits?
1 kb/s=1000 bps
Coaxial Cables consists of:
A copper conductor used to transmit the electronic signals. A layer of flexible plastic insulation surrounding a copper conductor. The insulating material is surrounded in a woven copper braid, or metallic foil, that acts as the second wire in the circuit and as a shield for the inner conductor. This second layer, or shield, also reduces the amount of outside electromagnetic interference. The entire cable is covered with a cable jacket to prevent minor physical damage.
What is a wired network?
A network that uses physical cables to transmit data.
What are the benefits of using a wired device over a wireless one?
A wired device does not need to share its access to the network with other devices. Each wired device has a separate communications channel over its Ethernet cable. This is important when considering some applications, such as online gaming, streaming video, and video conferencing, which require more dedicated bandwidth than other applications.
What are some drawbacks to wireless?
A wireless device will experience degradation in performance based on its distance from a wireless access point The further the device is from the access point, the weaker the wireless signal it receives. This can mean less bandwidth or no wireless connection at all
Gb/s
Gigabits per second
What is goodput?
Goodput is the measure of usable data transferred over a given period of time. Goodput is throughput minus traffic overhead for establishing sessions, acknowledgments, and encapsulation.
What are codes?
Groupings of bits used to provide a predictable pattern that can be recognized by both the sender and the receiver.
ISRs offer what?
ISRs offer a switching component with multiple ports, allowing multiple devices to be connected to the local area network (LAN) using cables Additionally, many ISRs also include an AP, which allows wireless devices to connect as well.
What are some benefits to using copper media?
Inexpensive Easy to install Has low resistance to electrical current
What kind of device offers both wired and wireless connectivity and commonly found in home network setups?
Integrated Service Routers (ISRs)
UTP cabling, terminated with RJ-45 connectors, is used for what?
Interconnecting network hosts with intermediate networking devices, such as switches and routers.
For instance, the physical layer hardware, media, encoding, and signaling standards are defined and governed by the:
International Organization for Standardization (ISO) Telecommunications Industry Association/Electronic Industries Association (TIA/EIA) International Telecommunication Union (ITU) American National Standards Institute (ANSI) Institute of Electrical and Electronics Engineers (IEEE) National telecommunications regulatory authorities including the Federal Communication Commission (FCC) in the USA and the European Telecommunications Standards Institute (ETSI)
What is a wireless range extender used for?
It can be used to regenerated the wireless signal to other parts of the house that are too far from the wireless access point.
How is data transmitted over copper cables?
It is transmitted as electrical impulses
What does digital bandwidth measuer?
It measures there amount of data that can flow from one place to another in a given amount of time.
The OSI physical layer provides what for the data link layer?
It provides the means to transport the bits that make up a data link layer frame across the network media. This layer accepts a complete frame from the data link layer and encodes it as a series of signals that are transmitted onto the local media. The encoded bits that comprise a frame are received by either an end device or an intermediate device.
Bandwidth is typically measures in what?
kilobits per second (kb/s) megabits per second (Mb/s) gigabits per second (Gb/s)
