week 3 Flashcards
what are NIC’s
They connect a device to the network
what are the 2 types of NICs
- -> WLAN NICs
- -> ethernet NICs
what are wlan used for
used for wireless connection
what are ethernet NICs
used for wired connection
what does physical layer of the OSI model do
–> provides the means to transport the bits that make up a data link layer frame across the network media
–> accepts a complete frame from the data link layer and encodes the frame by creating an electrical, optical or radio wave signals that represent the bits in each frame, to be transmitted onto the local media
the tcp/ip standards are implemented in __________ and governed by _______________
software, IETF (Internet Engineering Task Force)
how are the physical layer standards implemented
implemented in hardware
physical layer standards are governed by
governed by ISO, IEEE, ITU-T, ANSI TIA
what is bandwidth
- -> CAPACITY of a medium to carry data
- -> measures the amount of data that can flow from one place to another
what are the units of bandwidth measurement
- -> kilobits per second
- -> megabits per second
what factors play a role in determining the available bandwidth
- -> physical media properties
- -> current technologies
- -> laws of physics
what is throughput
- -> it is the measure of the transfer of bits across the media over a given period of time
- -> throughput is usually less than the specified bandwidth in physical layer implementations
what factors influence throughput
- -> amount of traffic
- -> type of traffic
- -> latency created by the network devices between source and destination
what is latency
refers to the delays for data to travel from one device to another
why is throughput slower than the slowest link in the path between source and destination
the slowest link creates a bottleneck to the throughput of the entire network
why is copper media used
less expensive
low electrical resistance
easy to install
what is transmission affected by
- -> distance: the longer the signal travels the more it deteriorates
- -> Electromagnetic interference / radio frequency interference
- -> crosstalk: the disturbance caused by electric/magnetic fields of a signal on one wire to the signal in an adjacent wire
what is done to counter emi / rfi
wrapped in metallic shieldings
require proper grounding connections
what is done to counter crosstalk
opposing circuit wire pairs are twisted together to cancel crosstalk
properties of optical fibre cables
–> optical fibre cables are used to transmit data over longer distances and at higher bandwidths via light impulses
–> transmits signals with less attenuation (energy loss) and is immune to emi/rfi
- -> type of cabling is used in
- -> enterprise networks
- -> long haul networks
- -> submarine networks
- -> FTTH (fiber to the home) networks
________ requires the highest installation skills
fiber optic
__________ has highest safety precautions
fiber optic
what is the distance of copper media
1 to 100 m
distance of fiber optic cables
1 to 100,000 m
bandwidth of copper medi
10Mbps to 10Gbps
bandwidth of fiber optic
10 Mbps – 100 Gbps
2 sub layers of data link layer
Logical link control
media access control
what is LLC
- -> upper sublayer defines the software processes that provide services to the network layer protocols
- -> places information in the frame to identify which network layer protocol is being used for which frame allowing different layer 3 protocols to use the same NIC and media
what is the Media access control layer
- -> lower sublayer
- -> defines how the hardware performs the media access process
- -> provides data link addressing and delimiting of data according to the physical signaling requirements of the medium and the type of data link layer protocol used
data link layer protocols govern how to __________________________
format a frame for use on different media
different _____- may be used for different media
protocols
what happens at each hop along the path
- -> an intermediary device accepts the frame from one medium and deencapsulates it
- -> packet is then encapsulated into a new frame with headers formatted for the specific medium the new frame is forwarded to
specific bit patterns denote the __________ of the frame
start and end
what are the generic frame field types
- -> frame start and stop indicator flags
- -> addressing
- -> Type
- -> Control
- -> data
- -> error detection
what are the frame start and stop indicator flags
–> used by the mac to identify beginning and end limits of the frame
what is addressing field
–> used by mac to identify source and destination nodes
what is the type field
used by llc to identify layer 3(network layer) protocols
what is control field
identifies special flow control services
what is data field
contains the frame payload data
what is error detection field
check for error detection
regulating the placement of data frames on the media is controlled by __________
media access layer
what are the different mac methods used to regulate the placing of frames onto different media
- -> contention based access
- -> controlled access
what are the characteristics of contention based access
- -> stations can transmit at any time
- -> collisions happen
- -> mechanisms are put in place to resolve contention for the media
what are the different contention based access technologies
CSMA/CD - collision detection (ethernet networks)
CSMA/CA - collision avoidance (wireless networks )
what happens in CSMA
- -> non deterministic
- -> network device can attempt to access the medium whenever it has data to send
- -> network data first detects if the media is carrying a signal
- -> if a carrier signal is detected on the media that means another device is transmitting data. It will wait for a while and then try again.
- -> if no carrier signal is detected the device transmits its data
- -> it is possible that 2 devices transmit at the same time creating a data collision. If this happens the data sent will be corrupted and needs to be resent.
what happens in collision detection
- -> monitors the media for collision
- -> if collision occurs, it sends a jamming signal
- -> all devices will stop sending and try again later
- -> used by traditional forms of ethernet
what happens in collision avoidance
- -> the sending device sends a notification across the media of its intent to use it
- -> once it receives a clearance to transmit, the device then sends the data
what are the characteristics in controlled access
- -> only one station can transmit at a time
- -> devices wanting to transmit must wait for their turn
- -> no collisions
- -> may use a token passing method
what are the controlled access technologies
- -> FDDI
- -> token ring
what is token ring
- -> schedules access deterministic
- -> network devices take turns, in sequence, to access the medium
- -> if the end device does not need to access the medium then the opportunity is passed to the next device
- -> the process is facilitated with the use of a token
- -> the sending device will acquire the token and place a frame onto the media, no other device can do so until that frame reaches the destination, releasing the token
why are deterministic methods inefficient
–> although controlled access is well ordered and provides predictable throughput deterministic methods are inefficient because a device has to wait for its turn before it can use the medium
what is topology of a network
relationship of the network devices and interconnections between them
what is physical topology
- -> refers to physical connections
- -> identifies how end devices and infrastructure devices are interconnected
what is logical topology
- -> refers to the way a network transfers frames from one node to the next
- -> logical signal paths are defined by data link layer
which topology is used in legacy ethernet networks
Bus topology
which topology is used in legacy token ring and FDDI
ring
which topology has the most availability but is the most expensive to implement
mesh
what is star topology
- -> end devices are connected to a central intermediate device
- -> most common topology
- -> in wan known as hub and spoke topology
field names in point to point protocol frame
flag address (broadcast address) control protocol data frame check sequence
ethernet frame fields
permeable (used for synchronization) destination address (mac) source address (mac) type data or payload frame check sequence (checks for damaged frames)
