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294 Cards in this Set
- Front
- Back
The OSI network model is considered one of the following.
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A formal standard.
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Which of the following application layer protocols are related to electronic mail?
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SMTP
POP IMAP |
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Which of the following are disadvantages of an N-Tier architecture over other architectures?
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Increased load on the network.
Increased management complexity. |
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Consider a circuit whose bandwidth is 16kHz utilizing QAM modulation. Assume the circuit has no noise. What is the resulting data rate (C) of the circuit?
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64kbps
QAM (Quadrature Amplitude Modulation) involves splitting the symbol into 8 different phases (requiring 3 bits), and two different amplitudes (requiring 1 bit). In total QAM symbol can represent 4 bits. Since the bandwidth is 16kHz, our resulting symbol rate is 16k. The data rate is calculated by multiplying the number of bits per symbol (4 with QAM) by the symbol rate (16k). |
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How much storage space would be required to store 24 hours of audio streamed to a computer at .75x106 bits/sec?
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8100 Megabytes
.75x106 bits per second is equal to .75Mbps. There are 60 seconds in a minute, 3600 seconds in an hour, and 86,400 seconds in a day. .75Mbps*86,400 seconds = 64,800Megabits. However, the solution is given in Megabytes. So we must divide 64,800 Megabits by 8 bits/byte. Thus, the correct solution is 8100 Megabytes |
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What is the symbol rate of a QAM circuit with a bandwidth of 3000Hz? Assume the circuit has no noise.
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3000
The symbol rate is usually equal to the bandwidth if there is little or no noise on the circuit. The adjective “QAM” (Quadrature Amplitude Modulation) involves splitting the symbol into 8 different phases (requiring 3 bits), and two different amplitudes (requiring 1 bit). In total QAM symbol can represent 4 bits. However, QAM is only used to calculate the data rate. The symbol rate of the circuit does not change regardless of the modulation used. Thus the symbol rate on this circuit is equal to the bandwidth which is 3000 |
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A T1 is a dedicated circuit made up of multiple channels inverse multiplexed together. What is the data transmission rate of one of these channels, assuming that there are no guardbands on the T1 circuit?
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64Kbps
A T1 is made up of 24 channels that each have a data rate of 64Kbp |
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Suppose you need to send 10Gb/s of data over a distance of 15 miles (between campuses). What type of cable below can support this criterion?
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Single Mode fiber optic cable
Single mode fiber optic cable is used for long distance transmissions (50 miles or more possible). Multi-mode fiber is often limited to shorter distances (1000 meters or less). Fiber optic cable can support data rates in excess of 10 Gigabits per second. Fiber solutions of 40Gigabits and greater are becoming more common! Coaxial and Category 6 cable cannot transmit data at these high data rates. In addition, Coaxial and Category 6 cable would need some type of repeater solution to transmit over long distances. |
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A digital signal is a rough approximation of its analog counterpart. The difference between a digital signal and its analog counterpart is called the “quantizing error”. Generally, there are two methods to reduce the quantizing error in the digital signal. Select the correct two methods below.
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Sample the source more frequently (oversampling).
Increase the number of amplitude levels Sample the source more frequently (oversampling) Digital signals do not have a phase or amplitude as an analog circuit would. Data compression techniques would only help increase the throughput in a circuit transmitting a circuit. It would not increase the accuracy of the signal sent. One correct choice is to increase the amplitude levels (more steps will minimize the differences between levels) which will lead to a smoother curve. Additionally, if the source circuit is sampled more frequently (often called oversampling), the resulting digital signal will be more accurate with respect to the analog source. |
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It is said the OSI network model suffered from differing philosophies during implementation at the ISO and ITU, and that consequently, the resulting network model became overly complex. From the statements below, select all that correctly explain why the model became complex
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The OSI model essentially attempted to shoehorn two different architectures into one model.
The OSI model attempted to integrate a “beads on a string” connection based architecture and a connectionless, layer based architecture into one model. |
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Assume you want to assign each of the 300 employees at your organization a unique identification number. Further assume that this number is in binary. Select the minimum number of bits needed for this unique identification number. You do not need to account for future growth of the organization.
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9 bits.
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From the alternatives below, select all that represent functions of an application program.
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Data storage
Presentation logic Data Access logic Application logic |
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Does the SMTP standard include the delivery of a message to the receiver's client computer? Why or why not?
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No, the SMTP standard was developed during the host architecture (mainframe) era. During this period, it made sense for a host to store all received user messages. Users would access their messages via a terminal.
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atch the layer of the internet model with its function.
Answer Question Correct Match Selected Match This layer ensures end to end connections between sender and receiver (including detecting lost messages). In addition, messages are broken up in smaller chunks for ease of transmittal. B. Transport Layer [None Given] This layer performs routing of messages by selecting the next device a message should be sent to. E. Network Layer [None Given] This layer is the user’s access to the network. User software encapsulates messages for transfer over the network. C. Application Layer [None Given] This layer transfers a series of electrical, radio, or light signals through a circuit. A. Physical Layer [None Given] This layer decides when to transmit messages across the network and formats the start and end of a message. In addition, this layer provides error detection and correction. D. Data Link Layer [None Given] |
atch the layer of the internet model with its function.
Answer Question Correct Match Selected Match This layer ensures end to end connections between sender and receiver (including detecting lost messages). In addition, messages are broken up in smaller chunks for ease of transmittal. B. Transport Layer [None Given] This layer performs routing of messages by selecting the next device a message should be sent to. E. Network Layer [None Given] This layer is the user’s access to the network. User software encapsulates messages for transfer over the network. C. Application Layer [None Given] This layer transfers a series of electrical, radio, or light signals through a circuit. A. Physical Layer [None Given] This layer decides when to transmit messages across the network and formats the start and end of a message. In addition, this layer provides error detection and correction. D. Data Link Layer [None Given] |
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Review the following scenario, then follow the subsequent instructions.
Company A decides to lease a T3 circuit for its main office. Company A has 4 small sites it wishes to connect to this T3. The circuit provider offers to run 7 T1 lines from each small site to the providers central office. The T1 lines (28 in total) will be combined and passed through the T3 which runs from the provider’s central office to the main office of Company A. At the main office of Company A, a router then processes the incoming T3. Note that a T3 circuit is composed of multiple T1 circuits. From the alternatives below, select all that correctly describe the process (occurring at the provider's central office) of combining the incoming T1 lines from the small sites to the T3 circuit. |
Inverse Multiplexing.
BONDING |
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From the alternatives below, select all that are multiplexing standards which use guard bands to separate the various signals operating on the circuit.
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Frequency Division multiplexing
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From the alternatives below, select all that are devices or mechanisms which convert analog signals to digital signals.
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a.
VOIP Telephone b. Codec d. Software for video, audio, and instant messaging (IM). e. Using a sound recording program to create an MP3 file. |
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From the alternatives below, select all that are true of 10 Mbps Ethernet.
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10Mbps Ethernet uses Manchester encoding.
10Mbps Ethernet uses a bi-polar signaling technique to transmit 1’s and 0’s. 10Mbps Ethernet can be transmitted over serial or parallel digital circuits. |
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Select the statement that correctly describes one benefit of a router.
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a.
A router will allow an interface of one data link layer protocol to communicate with an interface using a different data link layer protocol. |
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One of the following scenarios will result in the data encapsulated in a data link layer frame being re-encapsulated into a data link layer frame with a different data-link layer address. Select this scenario.
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A router receiving an Ethernet frame containing a network layer packet addressed to a node elsewhere on the network.
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Assume that a network interface card is assigned an IP address of 10.100.65.5 and a subnet mask of 255.255.248.0. From the alternatives below, select the network (subnet) address of this network interface card
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10.100.64.0
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Assume that a network interface card is assigned an IP address of 10.100.70.5 and a subnet mask of 255.255.248.0. From the alternatives below, select the network (subnet) address of this network interface card.
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None of the other answers are correct.
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Assume that a network interface card is assigned an IP address of 10.100.82.5 and a subnet mask of 255.255.128.0. From the alternatives below, select the network (subnet) address of this network interface card.10.100.82.5 and a subnet mask of 255.255.128.0?
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10.100.0.0
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Assuming that Ethernet is used at the data-link layer, select all statements that correctly explain how a network router determines where to route a network packet.
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The router examines the IP packet at the network layer and determines via the destination field if the packet was destined for itself, or if it should be routed to another subnet.
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Select all statements that correctly describe the Address Resolution protocol (ARP)
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A successful ARP request will ultimately lead to the sender receiving a MAC Address of another device on the network.
A successful ARP request will ultimately map an IP Address to an associated MAC Address. |
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Assume that a message exchange between a sender and receiver involves use of continous automatic repeat request (ARQ) as a method of flow control, and that the continous ARQ window size is 4. View the diagram below, and then choose the answer that best explains what will happen after the timeout. Note that the phrase “protocol data unit” is denoted by the acronym “PDU”.
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None of the other answers are correct.
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ssume that a message exchange between a sender and receiver involves use of continous automatic repeat request (ARQ) as a method of flow control, and that the continous ARQ window size is 4. View the diagram below, and then choose the answer that best explains what will happen after ACK7 is lost. Note that the phrase “protocol data unit” is denoted by the acronym “PDU”.
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None of the other answers are correct
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Select all statements that correctly describe the continuous automatic repeat request (ARQ) method of flow control, assuming that the initial continuous ARQ sliding window size is greater than 1.
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The receiver can reduce the size of the sliding window to slow down the sender’s send rate.
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Select all statements that correctly describe why synchronous transmission protocols are more efficient than asynchronous transmission protocols.
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Synchronous transmission protocols package multiple bytes of data into one frame.
Synchronous transmission protocols perform error and flow control on a per frame basis |
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Given a subnet with a subnet (network) address of 10.100.15.0 and a subnet mask of 255.255.255.0, indicate the number of IP addresses available for client devices on that subnet.
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254 IP addresses will be assignable to client devices.
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Given a subnet with a subnet (network) address of 10.100.0.0 and a subnet mask of 255.255.0.0, indicate the number of IP addresses available for client devices on that subnet.
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none of the other answers are correct
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Can IP addresses consistently serve to identify hosts (clients)?
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none of the other answers are correct
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From the statements below, select all that correctly describe quality of service (QoS) as it concerns data communication networks.
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QoS can be implemented using a protocol that prioritizes frames at the data link layer.
QoS can be implemented using a protocol that prioritizes packets at the network layer. Errors in memory can often look different than errors in a physical media (cable). |
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The transport and data-link layers both support error checking. From the alternatives below, select all that correctly explain why error checking can be useful in both layers.
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Errors in memory can often look different than errors in a physical media (cable).
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Select all issues that are associated with Wireless LANs (WLANs).
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With a PCF media access control, a hidden node problem can occur.
WLANs are prone to eavesdroppers. WLANS are prone to middle man attacks. |
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From the alternatives below, select all that correctly describe Wi-Fi when the 5GHz frequency is used.
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The 5GHz spectrum is more prone to attenuation than the 2.4GHz spectrum.
The 5GHz spectrum has greater bandwidth then the 2.4GHz spectrum. The 5GHz spectrum has a shorter range then the 2.4GHz spectrum. |
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From the scenarios below, select all that can cause major performance degradation on a switched Ethernet network.
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High levels of traffic on the switch and switch buffer overflow.
High levels of traffic on a switch programmed for 802.1q and Quality of Service. A broadcast storm on the switches. |
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From the alternatives below, select all that correctly describe the Ethernet protocol.
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Some versions of Ethernet use a shared bus.
Ethernet can operate at relatively high speeds. Ethernet is relatively inexpensive. |
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From the alternatives below, select all that correctly describe switched Ethernet.
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Frame collisions cannot occur on a full-duplex, switched network.
Switched Ethernet operates multiple point-to-point links on a network. Switched Ethernet improves security over Shared Bus Ethernet. |
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Select the method used by the 802.11 Wireless LAN protocols to deal with the “hidden node” problem.
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Request to Send and Clear to Send packets for channel reservation.
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From the alternatives below, select all that correctly describe Ethernet.
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Ethernet is a de facto standard.
All clients are always listening before a transmission begins. Ethernet uses Cyclical Redundancy Checking to detect errors. |
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From the alternatives below, select all that are cables capable of supporting gigabit transmission.
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Multi-Mode fiber optic cable
Single-Mode fiber optic cable. Category 5e UTP Category 5 UTP |
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From the options below, select all that correctly describe both Distributed Coordination Function (DCF) and Point Coordination Function (PCF).
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DCF and PCF are CSMA/CA based mechanisms.
DCF and PCF are commonly used with wireless based media. |
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From the options below, select all that correctly describe Distributed Coordination Function (DCF).
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DCF uses a form of stop-and-wait Automatic Repeat Request (ARQ).
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From the options below, select all that are design choices which will enhance the strength or performance of a wireless local area network (WLAN) signal.
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The use of a directional antenna.
Use of a 2.4Ghz WLAN technology instead of a 5Ghz WLAN technology. |
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From the options below, select all that are methods of switching.
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store and forward
cut through fragment free |
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A switch that has just been powered on will often broadcast messages to every port until it realizes (via creating a table) the data link layer addresses of devices connected on each port. This will occur even if devices are on differing subnets within this same switch. One of the methods below changes this behavior. When the method is incorporated, the switch will only broadcast packets to a subset of the switches ports. What is this method called?
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virtual LAN segmentation
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Select all terms that are protocols which do not support error control.
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ATM
Frame Relay |
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Select all alternatives that are disadvantages of a routed backbone network.
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Increased management complexity
Delays due to routing |
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Select all devices that are likely to be connected to the access layer of a network.
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network printers
client workstations |
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From the alternatives below, select the most common type of backbone network used within the distribution layer.
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collapsed backbone
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Select the layer of the internet network model for which a VLAN tag may be specified.
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data link layer
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Select the term that is an inter-switch protocol used by multi-switch VLANs.
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802.1q
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Select all alternatives that are components in a VLAN tag field.
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TPID – Tag Protocol Identifier
Priority CFI – Canonical Format Identifier VID – VLAN Identifier |
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How many of the available bits in a VID VLAN tag field are used for VLAN identification?
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12 bit
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The IEEE Ethernet Frame tagging standard is always required when creating VLANs on a switch.
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False
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Consider an organization with stable and predictable MAN/WAN traffic needs of 25Mbps between two sites. Which of the services below are suitable recommendations?
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Ethernet Services
T3 services SONET services |
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Consider a multi-site network that is at full capacity. Which options below might be recommended to reduce network demand?
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using data compression technology.
shifting network usage from peak to low demand times. configuring devices such as network printers to use a single broadcast protocol rather than many (IPX, TCP/IP, LAT, SNA, NetBEUI etc.) moving data closer to users. |
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When compared to the other WAN architectures, a full mesh WAN architecture provides the most benefits. Why is it not routinely deployed?
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The cost to connect every campus to every other campus is usually too high.
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Select all statements that correctly describe T1.
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A T1 frame is composed of 24 channels. Each channel takes turn outputting 8 bits to the frame.
A T1 is 1.544Mbps. However, only 1.536Mbps is usable. A T1 can be multiplexed or de-multiplexed (IMUX) to provide more or less capacity. |
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Select all statements that correctly describe the core layer of backbone networks.
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The core layer is the layer in the BN that connects different BN’s together.
The core layer is connected to the distribution layer on the backbone network. The core layer can feature routers or switches depending on the network architecture. |
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Select all alternatives that are disadvantages of collapsed backbones.
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They require longer cable runs.
They have an increased broadcast domain. They have a single point of failure. |
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Select all statements that correctly describe a benefit of a VLAN.
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A VLAN can be a benefit when trying to secure a network.
A VLAN can be given a tag to associate it with a particular VLAN ID. VLANs can make use of Quality of Service (QoS) for traffic prioritization. |
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Two of the following are true regarding VLAN tags. Select exactly two.
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A VLAN tag is stripped from the packet once it gets processed by a router.
A VLAN tag can be passed through a trunk port from one switch to another. |
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Select all alternatives that are a valid type of VLAN.
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MAC Address (Data Link layer) based VLANs
Switch Port based VLANs IP layer based VLANs Application layer based VLANs |
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From the statements below, select all that correctly describe a property of the source data units in datagram switching.
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Source data units may take a separate path to the destination node.
Source data units move simultaneously to the destination node. |
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Select all statements that correctly describe contention based media-access control.
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Contention based media-access control is not used by the Token Ring protocol.
Contention based media-access control offers its best performance when the volume of traffic is low. Contention based media-access control is used by the Ethernet protocol. |
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Match each technology to its most used media access control technique.
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Point Coordination Function (PCF)
Frequency-hopping spread spectrum (FHSS) Carrier Sense Multiple Access - Collision Detection (CSMA/CD) Distributed Coordination Function (DCF) |
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From the options below, select all that correctly describe a way 802.16d WiMax and 802.16e WiMax differs.
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802.16d is used in fixed point wireless solutions, while 802.16e is in mobile use wireless solutions.
802.16e is a competitor for public WiFi hotspots, while 802.16d is more commonly used to chain wireless access points across farther distances. |
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An IPSec virtual private network (VPN) will utilize methods to secure a message before sending it to its destination. This is accomplished by wrapping the Network, Transport, and Application layer PDUs with a packet of another protocol. What is this protocol called?
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Encapsulating Security Payload
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Select all statements that correctly describe an IPSec virtual private network (VPN).
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An IPSec VPN uses the UDP protocol at the transport layer.
An IPSec VPN encrypts at the network layer. |
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Select all alternatives that are types of symmetric encryption.
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AES
3DES |
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Select all statements that correctly describe asymmetric encryption.
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Asymmetric encryption generally uses complex algorithms.
Asymmetric encryption is often used in conjunction with symmetric encryption. |
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Select all statements that correctly describe a firewall.
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A firewall can be application, packet, and NAT based.
An application firewall can block traffic based on incoming traffic’s application layer port. A firewall can implement access control lists to secure network traffic between interfaces. |
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Select all statements that correctly describe Kerberos.
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Kerberos authentication does not send passwords across the network.
Kerberos generates a session key for clients, and clients use this session key to authenticate themselves. Kerberos is often used in Directory Services. |
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Select all statements that correctly describe the Secure Sockets Layer (SSL) protocol.
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SSL operates between the application layer and the transport layer.
After an SSL session has been initiated, a suitable encryption method is chosen by both the sender and receiver. |
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Select the kind of network that most closely describes how Internet Service Providers (ISPs) are organized.
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A hierarchical network
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Select all alternatives that are organizations that play a role in internet governance.
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IANA
IETF ICANN |
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Select all protocols that were developed by the Internet Engineering Task Force (IETF) organization.
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DHCP
|
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Select the correct definition of non-repudiation.
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None of the other answers is correct.
|
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Select all alternatives that are principle requirements that network security addresses.
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Confidentiality
Integrity |
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From the kinds of network security attacks below, select all that are active attacks in which the attacker sends some kind of transmission.
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Node A masquerading as Node B by claiming Node B’s MAC address
A hacker sending ICMP packets to a web server at a rate that cripples the server A hacker intercepting a message, modifying its contents, and transmitting this modified message to the original receiver |
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Select all alternatives that correctly describe hashing which occurs at the media-access control (MAC) layer, for example MD5 and SHA-1.
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MAC hashing is a tool used by the data-link layer to help determine if a message has been altered.
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Select all that would be significant challenges if an organization chose to secure their network solely with symmetric encryption.
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Symmetric encryption does not provide built-in key management mechanisms; therefore, key management could be a significant challenge.
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Select all alternatives that are a security service that digital signatures provide.
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Integrity
Authentication Non-Repudiation |
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Select the entity that is responsible for maintaining a Certificate Revocation List (CRL).
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The certifying authority that issued the certificate.
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Select all alternatives that correctly describe Key-Hashed Message Authentication Codes (HMACs).
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HMACs provide authentication.
HMACs do not require a key management infrastructure. |
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Select the organization responsible for allocating blocks of IP addresses.
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IANA
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Select the organization responsible for administering the allocation of domain names.
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ICANN
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Select all options below that can be a disadvantage of selecting network equipment from multiple vendors.
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vendors might not follow standards precisely and therefore two different vendor products might be have interoperability issues.
vendor products might be incompatible due to different interpretations of the same standard. |
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Select the version of SNMP that provides for authentication.
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SNMP v3
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SNMP was originally designed to use a connectionless transport protocol. Select the earliest version of SNMP that was designed to use a connection-oriented transport protocol instead.
|
SNMP v3
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Select all levels of network management that are typically the responsibility of the managed devices on the network.
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Sensor level
Agent level |
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Each managed network device stores data it gathers in its own virtual database. Select the name of this kind of virtual database.
|
Management Information Base
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Select all methods that can improve an existing network's uptime.
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Using redundant network devices in critical locations.
Using battery backup devices such as a UPS or generator to power equipment. Using network load balancers across a cluster of servers. Using robust virus and malware protection on client and server machines. |
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Select the alternative that is the correct definition a network partition.
|
A subnet on the network that is made inaccessible to other subnets due to connection failure.
|
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Select all correct descriptions of performance management on a network.
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Performance management involves investigating the changes in network traffic patterns and adjusting network policies that might affect these patterns.
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Select all correct descriptions of fault management on a network.
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There are two parts to fault management – Operational Response and Fault Management.
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Select the standardized network management protocol that was created first.
|
IEEE 802.1
|
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Select all management protocols that were initially proposed by the Internet Engineering Task Force.
|
SNMP
HEMS |
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Select all correct explanations as to why traditional network design is not suitable for modern networks.
|
Technology changes rapidly in modern networks.
Modern networks experience unprecedented traffic growth. The complexity of devices has increased, requiring additional management time, which increases staffing costs. |
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Select all alternatives that are key phases in the building block network design process.
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Technology Design phase
Cost Assessment phase Needs Analysis phase |
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Select all alternatives that are significant differentiators between the building block network design process and the traditional network design process.
|
The building block approach uses an iterative process to refine the network design.
|
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Select all alternatives that are goals of "baselining."
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To provide a clear picture of the current sequencing of operations.
To provide a baseline for current processing times for operations. |
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Select all alternatives that are deliverables in the Needs Analysis phase of the building block network design process.
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A list of mandatory applications the network should support.
|
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Select all alternatives that are elements included in the Technology Design phase of the building block network design process.
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The specification of base and advanced level computers to associated typical and high traffic areas.
Deciding on specific technology for circuits (i.e. T3, Ethernet, etc.) An estimation of average circuit traffic. An estimation of peak circuit traffic. A mathematical simulation (model) of the behavior of the network. |
|
Select all correct descriptions of load balancing and server clustering in a network.
|
The effects of a server failure can be mitigated when another server activates to take the processing load.
Servers receive load balanced requests via various mechanisms, including the “round robin” method. |
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Select all reasons why content caching and delivery approaches reduce network traffic.
|
Content delivery devices can store resources on many servers located in key geographical locations, many of which are close to the clients requesting the resources.
|
|
Select all devices that can be managed with SNMP.
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Routers
Switches Printers UPSs Gateways |
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Select all alternatives that are problems associated with Management Information Bases (MIBs).
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Standards committees have not imposed commonality with MIBs.
There is a proliferation of MIBs on the market, adding to the complexity of their use. |
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Select all characteristics exhibited on properly managed, large network.
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scalability
commonality orthogonality |
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A(n) _____________ is a set of rules that determine what a layer would do and provides a clearly defined set of messages that software at the layer needs to understand.
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protocol
|
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Which layer of the OSI model is responsible for ensuring that all packets sent are received by the destination station by dealing with end-to-end issues?
|
transport Layer
|
|
The most commonly used e-mail standard is:
|
Simple Mail Transfer Protocol
|
|
The American National Standards Institute:
|
is the coordinating organization for the United States' national system of standards
|
|
Which standards body is responsible for the development of local area network (LAN) standards?
|
IEEE
|
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In the Internet model, the application layer corresponds to the ________, layer(s) s of the OSI model.
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session, presentation and application
|
|
With a client-based architectures, one fundamental problem is that:
|
all data on the server must travel to the client for processing
|
|
A(n) __________ is the way in which the functions of the application layer software are spread among the clients and servers in the network.
|
application architecture
|
|
A "thin client" architecture approach:
|
places all or almost all of the application logic on the server
|
|
The protocol that makes it possible for a Macintosh web browser to be able to retrieve a Web page from a Microsoft Web server is called _____________________.
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Hypertext Transfer Protocol
|
|
Which of the following statements is correct?
|
Serial transmission is slower than parallel transmission.
|
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Select all terms that correctly identify hardware or software that is used to transform analog voice signals to digital signals and digital signals to analog signals.
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codec
|
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The _____________ of a circuit determines a circuit's capacity.
|
When sending four bits at a time using frequency modulation, the number of different frequency levels that would be needed would be _______.
|
|
A coding scheme that uses 12 bits to represent each character is capable of representing _________ different characters.
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4096
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How many bits per sample are required to sample an incoming signal 4,000 times per second using 64 different amplitude levels?
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6
|
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Which of the following media has the lowest error rates and the highest transmission speeds?
|
fiber optic cable
|
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Select all alternatives that correctly describe point-to-point circuits.
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Point-to-point circuits are called dedicated circuits.
Point-to-point circuits are dedicated to the use of the two computers |
|
Which of the following media can best withstand harsh environmental conditions?
|
fiber optic cable
|
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If each sample uses 16 bits, and the number of samples taken each second is 2,000, then what is the transmission speed of the circuit?
|
None of the other answers are correct
|
|
Synchronous transmission:
|
is used to transmit a "frame" or "packet" of data at a time
|
|
When a network protocol utilizes Automatic Repeat Request (ARQ), a NAK:
|
is sent by the recipient if the message contains an error
|
|
The loss of power a signal suffers as it travels from the transmitting computer to a receiving computer is:
|
attenuation
|
|
________ is the process of sending a signal to a client that gives its permission to transmit or asks it to receive.
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Polling
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_______________ is an effective way to deal with attenuation.
|
Adding repeaters or amplifiers to a circuit
|
|
Which items in the list below can cause errors during data transmission?
|
White noise, Impulse noise, Echo, Cross talk
|
|
When a network protocol utilizes Automatic Repeat Request (ARQ):
|
a receiver that detects an error in a message simply asks the sender to retransmit the message
|
|
Which of the following is true about the data link protocol PPP?
|
it is a byte-oriented protocol
|
|
Select all of the alternatives that are capabilities of the data link layer.
|
flow control
error detection and correction medium access control |
|
Select all of the alternatives below that are controlled access methods.
|
Poll/select
Token passing |
|
IPv4 Network Layer addresses are how many bits long?
|
32
|
|
Select all of the alternatives below that describe an action taken to address IP address exhaustion.
|
The introduction of a private addressing scheme
When block of addresses were distributed, fewer were given out and some large class A blocks were re-claimed Development of a new version of IP |
|
Routing between autonomous systems is called _______ routing.
|
exterior
|
|
How many unique identifiers would a 17-bit address field provide? Include any broadcast and network addresses identifiers in your calculation.
|
131,072
|
|
Assume that a network interface card is configured as follows:
IP Address: 192.168.43.3 Subnet Mask: 255.255.255.248 Select the subnet-directed broadcast address from the alternatives below. |
192.168.43.7
|
|
Select all statements that correctly identify differences between TCP and UDP.
|
TCP segments have bits to track sequences of packets, UDP datagrams to not track packet sequences.
UDP is connectionless while TCP is connection based. |
|
How many TCP fragments can be put in an IP packet?
|
1
|
|
TCP has a nominal 20 byte header for all PDUs. Some protocols have a separate type of PDU that carry no data for sending acknowledgments and flow control. Imagine that a new version of TCP utilized these seperate acknowledgment and flow control PDUs. How many bytes could be removed from the existing TCP header for the standard TCP PDU?
|
6
|
|
In a reliable transport service such as TCP, if a packet is duplicated, _______.
|
one of the duplicates is discarded
|
|
Assume there is a log which contains the following TCP/IP related information for TCP/IP network traffic on a local area network: Source IP address Destination IP address Source port Destination port What information would be needed to uniquely identify a TCP connection?
|
Source IP address, Destination IP address, Source port, Destination port
|
|
When the destination device receives a Ethernet frame with a bad CRC, the device does which of the following?
|
Discards the frame
|
|
Review the diagram below, then follow the subsequent instructions:
|
Select the protocol that that switches in this diagram must support, if a frame from the external network is to successfully reach a node on the LAN.
802.1D Spanning Tree protocol. |
|
From the alternatives below, select all that correctly describe a MAC address.
|
A MAC address is a data-link layer address.
|
|
Switched Ethernet:
|
usually enables all attached circuits to send or receive packets simultaneously
|
|
802.11g is backward compatible with which type of WLAN?
|
802.11b
|
|
Which of 802.11 standards offer additional security for WLAN applications?
|
802.11i
|
|
What is the maximum cable segment length for 10Base-T when using 100 Ohm unshielded Twisted Pair cable?
|
100 meters
|
|
Which security system changes the key for every frame it transmits to the client.
|
WPA
|
|
Select the form of media access control that Ethernet uses.
|
Carrier Sense Multiple Access/Collision Detection
|
|
Ethernet is a ___________ protocol, which means that there is no guarantee on the delivery time of a message.
|
Non-deterministic
|
|
Which of the following is not true about CSMA/CD?
|
It is used in token ring protocol LANs
|
|
Select all statements that correctly describe the data link layer.
|
The data link layer manages the physical layer.
The data link layer is comprised of two sub layers that each have their own responsibilities. |
|
Select all statements that correctly describe the network layer.
|
The network layer interfaces with both the transport layer and the data link layer.
The most-used network layer protocol is IP. Routers operate at the network layer. |
|
Most Countries, permit WLANs to operate in two frequency ranges that have been reserved for unlicensed transmissions those are
|
the 2.4GHz range and the 5GHz range
|
|
From the alternatives below, select all that correctly describe Wireless LANs (WLANs).
|
WLANS are effectively Half Duplex.
WLANs effectively use a shared bus architecture. |
|
A ________ is a software that contains components and programs that allow a computer on a network to serve requests from other computer for data and provide access to other resources such as printer and file systems.
|
Network operating system
|
|
If your LAN server is overloaded, which of the following should you not consider to solve the server problem?
|
replacing the cable with fiber optic cable
|
|
A Bluetooth network is called a(n) _________, which consists of no more than ______ slave devices, in addition to a master device.
|
Piconet, 7
|
|
When an access point configured to use EAP first discovers a new client the first thing the access point does is:
|
requires the user authenticate against a login server
|
|
Select the alternative which correctly indicates the duration, in microseconds, of a transmission of 4 bits on a 10 Gbps network.
|
.0004 microseconds
|
|
Select all statements that correctly describe backbone architecture layers.
|
The core layer is the part of the backbone which connects the different backbones together.
The distribution layer is the part of the backbone that connects the LANs together. |
|
Improving circuit capacity on a backbone network is one way to increase the network's performance.
|
True
|
|
Select all statements that correctly describe layers, switches, and gateways.
|
Routers connect two or more network segments that use the same or different data link protocols.
Layer-2 switches may connect the same or different types of cable. Multi protocol routers can route but not translate between several different network layer protocols. Gateways connect two or more networks that use the same or different data link and network protocols. |
|
Select all alternatives that correctly describe broadcast messages.
|
The majority of broadcast messages usually occur at the data link layer.
Broadcast messages can place a lot of demand on backbone networks. Broadcast messages usually consume more network resources on switched backbones than on routed backbones. |
|
Select all statements that correctly describe computers and devices that are part of a backbone network.
|
Some devices in a routed backbone network would include routers that might route packets to different subnets.
Most backbone devices are store-and-forward devices. |
|
Assume that there is a wide-area network (WAN) where the capacity of all its circuits and devices is currently being utilized. Select all statements that correctly describe ways to improve the performance of this WAN.
|
Upgrading the maximum bit-rate of circuits in the WAN
Upgrading the memory, processor, or I/O subsystem on the devices which connect the backbone networks to the WAN Replacing the devices which connect the backbone networks to the WAN with more powerful devices |
|
Select all statements that are correct in the context of a a wide-area network (WAN).
|
Circuits on a WAN that are not used to capacity can usually be downgraded to save on cost.
Adding a packet-switched service that is used only when demand exceeds circuit capacity is one way to improve performance on a WAN. |
|
What technology, under ideal conditions, will provide data rates up to 70 Mbps for up to 30 miles?
|
WiMax
|
|
A Basic rate interface provides communication circuit with _____ digital transmission channel and ____ control signaling channel.
|
Two 64 Kbps, one 16-Kbps
|
|
Assume that a dedicated-circuit network is using a ring architecture, and that the network is operating close to its capacity. If there is a failure of any one circuit, the transmission times will dramatically ___________.
|
increase
|
|
Choose all that are features of ATM networks. ATM networks _________________.
|
perform encapsulation of packets
are scalable provides extensive QoS information |
|
Select all alternatives that would likely increase demand on a regional wide-area network.
|
Moving data further from the applications and people who use them.
|
|
Select all statements that correctly describe the routed backbone architecture.
|
Routers are usually more expensive than switches.
Routed backbones do not forward data-link layer broadcast messages. Routing takes more time than switching. |
|
Select all statements that correctly describe gateways as a backbone network component.
|
The highest layer some gateways operate at is the application layer.
The highest layer some gateways operate at is the network layer. One common use of gateways is the enable LANs that use TCP/IP and Ethernet to communicate with mainframes that use other protocols |
|
The highest layer most switches operate at is the __________ layer.
|
data link
|
|
Switched backbone architectures use a(n) _____________ topology.
|
star
|
|
The VLAN environment is transparent to the sending and receiving computer.
|
True
|
|
A _______________ is particular type of network that uses circuits that run over the Internet but that appears to the user to be a private network.
|
virtual private network
|
|
In the context of a virtual private network, a tunnel can most accurately be described as _________________________.
|
a virtual circuit through the Internet.
|
|
Select all terms that are VPN tunneling protocols.
|
IPSEC
L2TP |
|
Which one of the following aspects of public/private key encryption provides authentication?
|
The fact that a digital signature encrypted with a user's private key can be decrypted with that user's public key and matched to the network message.
|
|
___________ refers to the fact that ISPs do not charge one another (at the same level) for transferring messages they exchange across an NAP or MAE.
|
Peering
|
|
A(n) ___________ contains a series of cable modems/multiplexers and converts the data from cable modem protocols into protocols needed for Internet traffic, before passing them to a router connected to an ISP POP.
|
cable modem termination system
|
|
DSL modems, cable modems, and dial-up modems connect to a ___________ , which is used by ISPs to authenticate its customers.
|
remote-access server.
|
|
The most important elements of the disaster recovery plan are _________ and ________ that enable the organization to recover its data and restart its application software should some portion of network fail.
|
backup and recovery controls
|
|
Asymmetric DSL uses ___________ multiplexing to create three separate channels over one local loop circuit.
|
frequency division
|
|
Select all alternatives below that are methods by which a secret key can be securely exchanged between two entities Entity A and Entity B.
|
TTP (trusted third party) delivering key to both Entity A and Entity B.
d. Entity A physically delivering the key to Entity B. |
|
A __________ is a trusted organization that can vouch for the authenticity of the person or the organization using the authentication.
|
certificate authority
|
|
What is the difference between VPNs and firewalls?
|
Providing a long-distance connection between two regional wide-area networks.
c. Providing Internet access to remote office buildings, apartment buildings, and hotels. |
|
________________ is in use when the set of hundreds of copper telephone lines that run from the telephone switch office is replaced by one fiber-optic cable that is run past each house or office in the neighborhood.
|
Passive Optical Networking
|
|
Select all statements that correctly describe accessing the Internet.
|
Users can connect to the Internet by using passive optical networking technologies.
Users can connect to the Internet by using DSL. Users can connect to the Internet by using a 56 Kbps dial up modem. Users can connect to the Internet by using WiMax technologies. Users can connect to the Internet by using satellite technologies. |
|
The ________ is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and smooth operation of the Internet, which has working groups and produces Requests For Coments and other relevant technical documents that influence the way people design, use, and manage the Internet
|
Internet Engineering Task Force
|
|
Select all alternatives that are groups that developed Internet 2.
|
UCAID
|
|
Select all alternatives that are fundamental techniques to determine if an intrusion is in progress in a stable network.
|
anomaly detection
|
|
Select all statements that correctly describe network controls.
|
Regardless of the effectiveness and number of controls on a network, an individual or department should still be responsible for the network's security.
Network controls can prevent, detect, and correct security breaches on a network. Developing network controls for a network is vital to that network's security. Controls should be examined on a regular basis to help ensure their effectiveness. |
|
Procedures, rules, hardware, and software that correct, prevent, or detect breaches in security are best classified as:
|
network controls
|
|
A (n) ______ is a special type of malware, not attached to any other program that spreads itself from computer to computer, without human intervention.
|
worm
|
|
A control spreadsheet used in risk assessment lists the __________, ________ and ________ that a network manager uses to assess the level of risk.
|
Assets, threats, and controls
|
|
Attacks that take advantage of a newly discovered security hole before a patch is developed are called ________ .
|
Zero day attacks
|
|
modulation
|
when we transmit data through telephone lines, we use the shape of the sound waves we transmit (in terms of amplitude, frequency, and phase) to represent different data values. We do this by transmitting a simple sound wave through the circuit (called a carrier wve) and then change its shape in different ways to represent a 1 or a 0. Modulation is the technical term for shape changes. Three fundamental types: amplitude, frequency, and phase modulation.
|
|
amplitude modulation
|
also called amplitude shift keying, the amplitude, or the height, of the wave is changed. One amplitude is the symbol defined to be 0, another is the symbol defined to be one. When one wishes to send a 1, it sends a high amplitude signal, when 0, a low.
|
|
frequency modulation
|
also called frequency shift keying, is a modulation technique whereby each 0 or 1 is represented by a number of waves per second. one frequency is defined to be a symbol of 1, and a different frequency is the symbol defined to be a 0.
|
|
phase modulation
|
also called phase shift keying. phase refers to the direction in which the wave begins. waves can also start down and to the right (known as a phase of 180*) with phase modulation, one phase symbol is defined to be a 0 and the other phase symbol is defined to be a 1. 0* can be a zero, 180* can be a 1.
|
|
quadrature amplitude modulation (QAM)
|
involves splitting the symbol into eight different phases(3 bits) and two different amplitudes (1 bit) for a total of 16 possible values.Thus, one symbol in QAM can represent 4 bits, while 256-QAM sends 8 bits per symbol. 64-QAM and 256-QAM are commonly used in digital TV services and cable modem Internet services.
|
|
bit rate
|
the number of bits per second
|
|
baud rate
|
the number of times a second that the communication circuit changes
|
|
Five layer networking model
|
serves primarily the protocols known as TCP and IP, jointly TCP/IP. The User datagram protocol is also served by this model. The internet model evolved from the work of thousands people who developed pieces of the Internet
|
|
physical layer
|
the physical layer is the physical connection between the sender and receiver. Its role is to transfer a series of electrical, radio, or light signals through the circuit. The physical layer includes all the hardware devices and physical media.
|
|
The data link layer
|
is responsible for moving a message form one computer to the next computer in the network path from the sender to the receiver. The data link layer in the Internet model performs the same three functions as the data link layer in the OSI model. First it controls the physical layer by deciding when to transmit messages over the media. Second, it formats the messages by indicating where they start and end. Third, it detects and may correct any errors that have occurred during transmission.
|
|
the network layer
|
it performs routing, in that it selects the next computer to which message should be sent. second, it can find the address of that computer if it doesnt already know it.
|
|
application layer
|
the application software used by the network users and includes much of what the OSI model contains in the application, presentation, and session layers. The users access to the network.
|
|
datalink layer
|
ethernet frame- the data link layer formats the message with start and stop markers, adds error checking information, places the IP packet inside an ethernet PDU, whihc is called an Ethernet frame, and instructs the physical hardware to transmit the Ethernet frame, which contains the IP packet.
|
|
network layer
|
IP- The network layer on the Internet uses a protocol called IP which has its rules and PDUs. IP selects the next stop on teh message's route through.It places the TCP segment inside an IP PDU.
|
|
application layer
|
HTTP
|
|
Processes and application layer
|
Provides applications services to users and programs
|
|
transport layer
|
handles data consistency functions, provides a reliable byte stream between two
|
|
Internet(network) layer
|
provides network addressing and routing, and does so in such a way as also to provide common address space across multiple lower level protocols. this makes possible the interconnection of networks that characterizes the Internet. The IP protocol operates at this level
|
|
network (datalink) layer
|
This layer contains whatever IP will run over, ethernet, token-ring, and FDDI.
|
|
physical layer
|
referrers to all hardware under the network layer
|
|
encapsulation in terms of networking
|
this happens when a PDU at a higher level is put inside the PDU of a lower level. The opposite is known as decapsulation
|
|
standards a standard defines a set of rules
|
called protocols
|
|
application architectures
|
the way in which the functions o fhte application layer software are spread among the clients and servers in the network. divided into four general functions (data storage, data access logic, application(business) logic, and presentation logic
|
|
data storage
|
where the data is stored and retrieved
|
|
data access logic
|
the processing required to access the data
|
|
presentation logic
|
the presentation of information to the user and the acceptance of user commands
|
|
host-based architectures
|
the server performs all the work, usually a large mainframe computer, while the clients were typically terminals. The clients meerly captured keystrokes, sent them to the server for processing, and accepted instructions from the server on what to display. Two problems, first the server must process all the messages and these types of architectures are usually expensive to upgrade
|
|
client-based architectures
|
the client performs all the work. with client-based architectures, the clients are personal computers on a lan and the server is usually another personal computer on the same network. When a client-based architecture is in place, the clients are personal computers on a lan, and the server is usually another personal computer on the same network. The server essentially acts as a storage device. Storing a document on the file server after being written in a word processor is an example of this architecture in place. Fundamental problem is that all data on the server must travel to the client for processing. This can overload network circuits.
|
|
client-server architectures
|
the work is shared between the servers and clients. There is some division of the responsibility among the client and the server. Using a web browser to get pages from a web server is using a client-server architecture. A strength of this architecture is that they enable software and hardware from different vendors to be used together. Middleware is typically used to ease this process
|
|
peer-to-peer architectures
|
the computers are both clients and servers. These can be installed anywhere on the network, even globally, very resilient to the failure of any one computer. Difficulty is finding the data.
|
|
Two-tier
|
the server is responsible for the data and the client is repsonsible for application and data. Two sets of computers, one set of clients.
|
|
Three-tier
|
three sets of computers
|
|
thin-client
|
places little or no application logic on the client
|
|
thick-client
|
places all or almost all of the application logic on the client
|
|
scalability
|
the client-server architecture provides the best scalability, or the ability to increase (or decrease) the capacity of the servers to meet changing needs.
|
|
Http request
|
has three parts- the request line, the request header, and the request body
|
|
http response
|
has an http response status, a response header, and a response body
|
|
multiplexing
|
breaking on high-speed physical communication circuit into several lower-speed logical circuits so that many different devices can simultaneously use it. Done in multiples of four. Four type of multiplexing: Frequency Division Multiplexing (FDM), time division multiplexing (TDM), statistical time division multiplexing (STDM), and wave-length division multiplexing (WDM).
|
|
Frequency division multiplexing
|
dividing the circuit horizontally so that many signals can travel a single communication circuit simultaneously. Each channel is a separate logical circuit, and the devices connected to them are unaware that their circuit is being multiplexed. Guardbands are the unused portions of the circuit that separate these frequencies from each other. Total capacity is divided by the number of circuits + guardbands
|
|
Time Division Multiplexing
|
Shares a communication circuit among two or more computers by having them take turns, dividing the circuit. There are no guardbands, so it's more efficient.
|
|
Statistical Time Division Multiplexing
|
statistical analysis to mutliplex
|
|
Inverse Multiplexing
|
combines several low speed circuits into one high speed circuit BONDING
|
|
Data rate
|
signifies the rate of bits over a connection, meaning the number of bits that flow per a period of time (usually seconds
|
|
transmission efficiency
|
indicates the percentage of the informational data sent with respect to the total data sent. the total data sent includes the overhead data needed by the network protocols
|
|
transmission efficiency
|
the number of information bits/total number of bits transmitted. transmission efficiency(2)
|
|
transmission efficiency(3)
|
the overhead header and footer bits must be summoned from all protocols invloved for a transmission, to determine the number of overhead bits.
|
|
effective data rate
|
transmission efficiency * maximum data rate
|
|
ip addressing
|
has an address written in the form 192.168.1.1 for one node to reach another node using the ip protocol, it must know its IP address. each node can send packets directly on the same subnet.
|
|
subnet
|
a subnet provides a way to divide LANs by logically grouping nodes by IP number
|
|
subnet mask
|
uses a subnet mask to determine if the address is on the same subnet
|
|
subnet formula
|
Bitwise and source IP with subnet mask Bitwise and destination IP with subnet mask If both results are equal, the node is in the same subnet. Send it directly. If both results are not equal, the node is in a different subnet. Use the routing table to determine where to send it, usually to the default gateway.
|
|
wide area network(WAN)
|
connect backbone networks and regional WANs across any distance, when organizations use WANs they have a need for a private network to span campuses located geographically far apart
|
|
sl
|
dsl is a family of techniques that combines analog transmission and FDM to provide a set of voice and data circuits. There are many different types of DSL. A DSL modem, called customer premises equipment (CPE), is installed in the customer's home. The modem is first and FDM device that splits the physical circuit into three logical circuits: standard voice, upstream and downstream. TDM is then used within the two data channels to provide a set of one or more individual channels that can be used to carry data.
|
|
Broadband technologies
|
higher speed communications than traditional modems. Internet technologies cannot be used for general purpose networking
|
|
DSL
|
a family of point-to-point technologies designed to provide high-speed data transmission over traditional telephone lines. The CPE in DSL includes a line splitter that is used to separate the traditional voice telephone signals into the normal telephone system. If data fails, normal phones are not affected. Local loops are connected to the Main Distribution facilitiy, which works like the CPE line splitter. DSL Access Multiplexer converts it into ATM data. DSL is a point to point technology
|
|
ADSL
|
uses frequency division multiplexing to create three separate channels over the local loop circuit. ADSL is asymmetric because the upload and download speeds are not the same.
|
|
Cable
|
Data over cable service interface specification DOCSIS. Hybrid fiber coax networks. Cable modems use shared multipoint circuits, each user is competing with other users for the available capacity. The cable runs to an optical fiber node, which has an optical-electrical converter to convert between the coaxial cable and the fiber wire. The fiber nodes are connected to the cable company distribution hub through two seaparate circuits (upstream/downstream)
|
|
Cable modem termination system (CMTS)
|
a series of cable modems/multiplexers and converts the data from cable modem protocols into protocols needed for internet traffic. Downstream contains ordinary video and data.
|
|
fixed wireless
|
the commercial name for a set of standards developed by the IEEE. Can be used to connect a house or an office into the Internet. Works much in the same way as wifi. WiMax uses the 2.3 2.5 and 3.5 frequency ranges. Maximum ranges from 3 to 10 miles, depending interference and obstacles
|
|
wireless broadband
|
wimax
|
|
symmetric encryption
|
single-key encryption has two parts, the algorithm and the key. In symmetric encryption, the communicating parties must share the one key. Because the same key is used to encrypt and decrypt, key management can be important
|
|
data encryption standard (DES)
|
older version of the new 3DES standard
|
|
Advanced encryption standard
|
128,192,256 bits
|
|
asymmetric encryption
|
Public key encryption, RSA, Public Key Infrastructure PKI, public key encryption is inherently different from symmetric single-key systems like DES. There are two keys one, the public key, is used to encrypt the message, and a second, a private key, is used to decrypt. 512, 1024, 2048
|
|
3. (10 pts) Assume that you are running HTTP 1.0, and requesting an HTML page which contains two images in addition to the HTML content. How many request response pairs would there be in such a scenario? Describe how a Web browser and a Web server work together to send a Web page to a user in the above scenario.
|
.
|
|
7. (10 pts) How does digital data differ from analog data?
|
.
|
|
(20 pts) Assume we need to download the text of a paperback book at the rate of 30 pages per minute. Further assume that the number of lines per page is 23, and the number of characters per line is 65. What is the required bit rate of the channel? Show all of your work for full credit.
|
.
|
|
10 pts) Assume that a node SENDER wants to transmit a message to a node RECEIVER at the data link layer. Review the scenarios below, which describe the success or failure of the initial transmission of the message or the ACK. For each scenario, indicate a complete and numbered series of steps describing exactly how the SENDER and RECEIVER successfully transmit the message. The last step for each scenario should be the successful acknowledgment from the receiver.
If you are having difficulty with this problem, it may help you to draw the numbered steps (drawing the steps is optional). Scenario 1: The message is initially transmitted with an error. Scenario 2: The message is transmitted without an error. Scenario 3: The ACK for the message is initially lost. Scenario 4: The message is initially lost. |
.
|
|
Identify and explain three important factors to consider when determining whether to use a large or a small frame (or PDU – protocol data unit) size when transmitting data over a network.
|
.
|
|
3. (10 pts) Determine the effective data rate of a 128 kbps connection in an asynchronous transmission using 7-bit ASCII, 1 parity bit, 1 start bit, and 1 stop bit. Show your work to receive credit.
|
.
|
|
A web browser sends a message using HTTP over TCP/IP over Ethernet. The web browser request consists of 130 bytes. The HTTP protocol adds an additional 50 bytes of overhead to the request as part of the HTTP PDU. There is neither noise nor errors on the circuit involved in the transmission.
Calculate the overall transmission efficiency of the web browser's request. You may assume that nominal TCP and IP headers are used, both of which consist of 20 bytes. Show your work to receive credit. |
.
|
|
PGP
|
a freeware public key encryption package developed by phillip zimmermann
|
|
Secure Sockets Layer
|
Is an encryption protocol widely used on the web. Operates between the application layer software and the transport. It encrypts outbound packets comoing out of the application layer before they reach the transport layer and decrypts inbound packets coming out of the transport layer before they reach the application layer.
|
|
IP Security Protocol (IPSEC)
|
Sits between IP at the network layer and TCP/UDP at the transport layer. It is done using IKE
|
|
Internet Key Exchange
|
Both parties generate a random key and send it to the other using an encrypted authenticated PKI process and then put these two numbers together to produce the key.
|
|
Authentication
|
Passwords, access cards, biometrics
|
|
Intrusion Prevention Systems
|
designed to detect an intrusion and take action to stop it.
|
|
carrier sense multiple access with collision avoidance (CSMA/CA)
|
computers listen before they transmit and if no one else is transmitting, they proceed with transmission. wifi
|
|
carrier sense multiple access with collision detection (CSMA/CD)
|
ethernet uses a contention based media access control technique called CSMA/CD. it waits until the circuit is free and then transmits. a device can listen while transmitting. If it detects any signal other than its own, it will send out a jamming signal and assume a collision has occurred. It waits a random period of time before deciding to re-transmit.
|
|
point coordination function
|
virtual carrier sense method. Any computer wishing to transmit first sends a request to transmit to the AP, to which if the AP is going to let them broadcast replies with a clear to transmit CTS
|
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Controlled-access methods provide poorer performance in low-traffic networks
because computers must wait for permission before transmitting rather than just waiting for an unused time period. However, controlled-access techniques work better in high-traffic WLANs because without controlled access there are many collisions. Think of a large class discussion in which the instructor selects who will speak (controlled access) versus one in which any student can shout out a comment at any time. |
Controlled-access methods provide poorer performance in low-traffic networks
because computers must wait for permission before transmitting rather than just waiting for an unused time period. However, controlled-access techniques work better in high-traffic WLANs because without controlled access there are many collisions. Think of a large class discussion in which the instructor selects who will speak (controlled access) versus one in which any student can shout out a comment at any time. |
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WEP
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With
WEP, the AP requires the user to have a key in order to communicate with it. All data sent to and from the AP is encrypted so that it can only be understood by computers or devices that have the key (encryption is discussed in more detail in Chapter 10). If a computer does not have the correct WEP key, it cannot understand any messages transmitted by the access point and the access point will not accept any data that is not encrypted with the correct key |
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With Extensible Authentication Protocol (EAP), the WEP keys are produced
dynamically, much like the way in which a DHCP server is used to dynamically produce IP addresses. |
With Extensible Authentication Protocol (EAP), the WEP keys are produced
dynamically, much like the way in which a DHCP server is used to dynamically produce IP addresses. |
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WPA
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WPA
works in ways similar to WEP and EAP: every frame is encrypted using a key, and the key can be fixed in the AP like WEP or can be assigned dynamically as users login like EAP. Key is changed with every frame. |
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802.11i
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WPA2 It uses EAP to obtain a master key—in other words, the user logs in to a login
server to obtain the master key. Armed with this master key, the user’s computer and the AP negotiate a new key that will be used for this session until the users leaves the WLAN. 802.11i uses the Advanced Encryption Standard (AES) discussed in Chapter 10 as its encryption method. |