Cisco Chapter 4 Flashcards
Business offers wireless capability, devices on a wireless network must be connected to a ????
Wireless access point (WAP).
Switch devices and ????? are often two separate dedicated devices within a network implementation
wireless access points
In many homes, individuals are implementing ??? .
home integrated service routers (ISRs)
What does an ISRs do?
switching component with multiple ports,
multiple devices to be connected to the LAN using cables.
Conencts with AP(access point)
??? connect a device to the network.
Network Interface Cards(NIC)
Ethernet NICs
Wired connection
WLAN (Wireless Local Area Network) NICs are used for wireless.
Wireless connection
A ????? can be used to regenerate the wireless signal to other parts of the house that are too far from the wireless access poin
Wireless range extender
All wireless devices must share access to the ???connecting to the wireless access point.
airwaves
A wired device does not need to share its access to the network with other devices. Each wired device has a separate ??? over its Ethernet cable.
communications channel
The OSI physical layer provides the means to ??? the ?? that make up a ???? frame across the network media.
transport/bits /data link layer
The OSI physical layer accepts a ??? from the ??? and ?? it as a series of signals that are ?? onto the local media.
complete frame/data link layer/encodes/transmitted
The OSI physical layer encoded bits that comprise a frame are received by either an ??? or an ????
end-device/ intermediate device.
2: The physical layer ?? the ?? and creates the electrical, optical, or radio wave signals that represent the bits in each frame.
These ?? are then sent on the media, one at a time.
encodes/frames/bits /signals
1: The user data is ?? by the transport layer, placed into ?? by the network layer, and further ?? into frames by the data link layer.
segmented/packets/encapsulated
1: The user data is segmented by the ??, placed into packets by the ??, and further encapsulated into frames by the ??
transport layer/ transport layer/data link layer
2: The ?? encodes the frames and creates the electrical, optical, or radio wave signals that represent the bits in each frame.
These signals are then sent on the media, one at a time.
physical layer
3: The destination node ??? retrieves these individual signals from the media, restores them to their bit representations, and passes the bits up to the ?? as a complete frame.
physical layer/data link layer
3: The destination node physical layer retrieves these ?? from the media, restores them to their ??, and passes the bits up to the data link layer as a ??
individual signals/bit representations/complete frame
???: The signals are patterns of electrical pulses.
??: The signals are patterns of light.
??: The signals are patterns of microwave transmissions.
Copper cable/Fiber-optic cable/Wireless
The services and protocols in the TCP/IP suite are defined by the
Internet Engineering Task Force (IETF).
Bandwidth
is the capacity of a medium to carry data in a given amount of time.
measured in kilobits per second (kb/s),
megabits per second (Mb/s)
gigabits per second (Gb/s).
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.
This all plays a role in determining the available bandwidth.
The properties of physical media
The technologies chosen for signalling/detecting network signals
Physical media properties,
current technologies,
laws of physics
Throughput
Throughput is the measure of the transfer of bits across the media over a given period of time.
Due to a number of factors, throughput usually does not match the specified bandwidth in physical layer implementations. They are:
The amount of traffic
The type of traffic
In an internetwork or network with multiple segments, throughput cannot be faster than the slowest link in the path from source to destination. 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.
There are many online speed tests that can reveal the throughput of an Internet connection. The figure provides sample results from a speed test.
There is a third measurement to assess the transfer of usable data that is known as 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.
Latency
refers to the amount of time to travel from one given point to another.
The physical layer produces the
representation and groupings of bits as voltages, radio frequencies, or light pulses.
Various standards organizations contributed to the definition of the physical, electrical, and mechanical properties of the media available for different data communications. These specifications guarantee that cables and connectors will function as anticipated with different data link layer implementations.
As an example, 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
Encoding
line encoding a method of converting a stream of data bits into a predefined “code”.
encoding is the method/ pattern used to represent digital information.
Like Morse
The physical layer standards address ?? functional areas:
3
Physical Components
Connectors that transmit and carry the signals to represent the bits that are all specified in standards associated with the physical layer
Signaling
The physical layer generates the electrical, optical, wireless signals that represent “1” and “0” on the media.
The method of representing the bits is called the signalling method.
The physical layer standards must define what type of signal represents a “1” and what type of signal represents a “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 signalling 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).
The nature of the actual signals representing the bits on the media will depend on the signaling method in use.
Figure 2 illustrates the how AM and FM techniques are used to send a signal
The physical layer hardware, media, encoding, and signalling standards are defined by
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)
Regional cabling standards groups
CSA (Canadian Standards Association), CENELEC (European Committee for Electrotechnical Standardization), and JSA/JIS (Japanese Standards Association), developing local specifications.
Manchester encoding represents a 0 bit by a high to low voltage transition, and a 1 bit is represented as a low to high voltage transition
The transition occurs at the middle of each bit period. This type of encoding is used in 10 b/s Ethernet. Faster data rates require more complex encoding and is used in older Ethernet standards
Throughput
the measure of the transfer of bit’s across the media
Bandwith
The capacity of a medium to carry data
Wireless
A pattern of microwaves to represent bits
Copper cable
\+ electrical pulses \+inexpensive \+easy to install, \+low resistance to electrical current - limited by distance - signal interference.
signal attenuation
The longer the signal travels, the more it deteriorates.
Electromagnetic interference (EMI) radio frequency interference (RFI)
EMI and RFI signals can distort and corrupt the data signals being carried by copper media. Potential sources of EMI and RFI include radio waves and electromagnetic devices, such as fluorescent lights or electric motors.
Crosstalk
- Crosstalk 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, crosstalk can result in hearing part of another voice 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 an adjacent wire.
To counter the negative effects of crosstalk,
copper cables have opposing circuit wire pairs twisted together, which effectively cancels the crosstalk.
Select the cable type or category most suited to a 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.
There are 3 types of copper media used in networking
Unshielded Twisted-Pair (UTP)
Shielded Twisted-Pair (STP)
Coaxial
Coper cables are used to interconnect nodes
These standards specify the mechanical dimensions of the connectors and the acceptable electrical properties of each type.
Each type of connection/accompanying devices has cabling requirements stipulated by physical layer standards.
Networking media use modular jacks and plugs to provide easy connection and disconnection
A single type of physical connector may be used for multiple types of connections.
