Podcast
Questions and Answers
Which of the following best describes the function of a packet switch in a computer network?
Which of the following best describes the function of a packet switch in a computer network?
- It generates header bytes for each data segment before transmission.
- It converts data into different physical media types, such as from copper wire to optical fiber.
- It receives packets on an incoming communication link and forwards them on an outgoing link. (correct)
- It assembles data segments back into their original form at the destination end system.
Considering a packet-switched network analogous to a transportation network, what component in the packet network corresponds to a highway intersection in the transportation network?
Considering a packet-switched network analogous to a transportation network, what component in the packet network corresponds to a highway intersection in the transportation network?
- Communication Link
- Packet Switch (correct)
- Data Segment
- End System
What is the primary role of link-layer switches compared to routers in a typical network architecture?
What is the primary role of link-layer switches compared to routers in a typical network architecture?
- To manage routing protocols within the network core.
- To regulate the transmission rate of data over communication links.
- To forward packets primarily within access networks. (correct)
- To handle the segmentation and reassembly of data.
When a sending end system prepares data for transmission across a network, what process is involved after the data is segmented?
When a sending end system prepares data for transmission across a network, what process is involved after the data is segmented?
A network engineer is troubleshooting a slow data transfer rate between two end systems. Which factor is MOST likely to be the cause of the bottleneck?
A network engineer is troubleshooting a slow data transfer rate between two end systems. Which factor is MOST likely to be the cause of the bottleneck?
If annual global IP traffic is predicted to reach nearly five zettabytes by 2022, what is the equivalent value in bytes?
If annual global IP traffic is predicted to reach nearly five zettabytes by 2022, what is the equivalent value in bytes?
In a packet-switched network, what is the MOST significant reason for segmenting data into packets before transmission?
In a packet-switched network, what is the MOST significant reason for segmenting data into packets before transmission?
What is the term used to describe the complete sequence of communication links and packet switches that a packet traverses from the sender to the receiver?
What is the term used to describe the complete sequence of communication links and packet switches that a packet traverses from the sender to the receiver?
Which of the following analogies best represents the relationship between the Internet and its components?
Which of the following analogies best represents the relationship between the Internet and its components?
Why is the interconnection of ISPs essential for the functionality of the Internet?
Why is the interconnection of ISPs essential for the functionality of the Internet?
What is the primary role of upper-tier ISPs in the Internet infrastructure?
What is the primary role of upper-tier ISPs in the Internet infrastructure?
Which of the following is NOT a typical function of an Internet Service Provider (ISP)?
Which of the following is NOT a typical function of an Internet Service Provider (ISP)?
What distinguishes upper-tier ISPs from lower-tier ISPs?
What distinguishes upper-tier ISPs from lower-tier ISPs?
What is the role of protocols like TCP/IP in the Internet?
What is the role of protocols like TCP/IP in the Internet?
If a user accesses the Internet through a local coffee shop's WiFi, which type of ISP is providing the network access?
If a user accesses the Internet through a local coffee shop's WiFi, which type of ISP is providing the network access?
An end system wants to send data to another end system on a different network. Which of the following describes the most likely path the data will take?
An end system wants to send data to another end system on a different network. Which of the following describes the most likely path the data will take?
Which network environment is LEAST susceptible to packet sniffing?
Which network environment is LEAST susceptible to packet sniffing?
A network administrator suspects a compromised machine is acting as a packet sniffer. Which strategy would be MOST effective in detecting this activity?
A network administrator suspects a compromised machine is acting as a packet sniffer. Which strategy would be MOST effective in detecting this activity?
An attacker plants a packet sniffer on an institution's access router. What type of information is MOST likely to be compromised?
An attacker plants a packet sniffer on an institution's access router. What type of information is MOST likely to be compromised?
How might an organization BEST mitigate the risk of packet sniffing on its wireless network?
How might an organization BEST mitigate the risk of packet sniffing on its wireless network?
Which security measure would be MOST effective in preventing a malicious insider from deploying a packet sniffer on a wired Ethernet LAN?
Which security measure would be MOST effective in preventing a malicious insider from deploying a packet sniffer on a wired Ethernet LAN?
Which of the following actions could a compromised host perform as part of a botnet?
Which of the following actions could a compromised host perform as part of a botnet?
A self-replicating malware infects a host. What is the most likely next step this malware will take?
A self-replicating malware infects a host. What is the most likely next step this malware will take?
What is the primary goal of a Denial-of-Service (DoS) attack?
What is the primary goal of a Denial-of-Service (DoS) attack?
Which type of attack involves exploiting a weakness in an application or operating system by sending specific, malicious messages?
Which type of attack involves exploiting a weakness in an application or operating system by sending specific, malicious messages?
Why is malware a significant threat to computer networks?
Why is malware a significant threat to computer networks?
Which of the following is NOT a typical target of Denial-of-Service (DoS) attacks?
Which of the following is NOT a typical target of Denial-of-Service (DoS) attacks?
How do bad actors typically control and leverage a botnet?
How do bad actors typically control and leverage a botnet?
Which outcome is LEAST likely to result from a successful vulnerability exploitation?
Which outcome is LEAST likely to result from a successful vulnerability exploitation?
According to the content, what is the relationship between traffic intensity and queuing delay when the road or network is already typically congested?
According to the content, what is the relationship between traffic intensity and queuing delay when the road or network is already typically congested?
In the context of packet-switched networks, what happens when a packet arrives at a router with a full queue?
In the context of packet-switched networks, what happens when a packet arrives at a router with a full queue?
How does a packet loss typically appear from the perspective of an end-system in a packet-switched network?
How does a packet loss typically appear from the perspective of an end-system in a packet-switched network?
Why is packet loss probability an important performance metric in packet-switched networks, in addition to delay?
Why is packet loss probability an important performance metric in packet-switched networks, in addition to delay?
What is the typical response to packet loss in order to ensure reliable data transfer from source to destination?
What is the typical response to packet loss in order to ensure reliable data transfer from source to destination?
Consider a network link where the packet arrival rate is consistently higher than the link's capacity. What is the expected long-term behavior of the queue at this link, assuming a finite queue capacity?
Consider a network link where the packet arrival rate is consistently higher than the link's capacity. What is the expected long-term behavior of the queue at this link, assuming a finite queue capacity?
A network administrator observes a sudden spike in traffic intensity on a critical link. Based on the content provided, predict the most likely immediate consequences.
A network administrator observes a sudden spike in traffic intensity on a critical link. Based on the content provided, predict the most likely immediate consequences.
Imagine a scenario where a router's queue has reached its maximum capacity, and several packets are dropped. What actions might higher-layer protocols (e.g., TCP) take in response to this packet loss?
Imagine a scenario where a router's queue has reached its maximum capacity, and several packets are dropped. What actions might higher-layer protocols (e.g., TCP) take in response to this packet loss?
In a network with a server, a router, and a client, where Rs is the rate of the server-router link and Rc is the rate of the router-client link, what determines the server-to-client throughput when transferring a file?
In a network with a server, a router, and a client, where Rs is the rate of the server-router link and Rc is the rate of the router-client link, what determines the server-to-client throughput when transferring a file?
If Rs (server-router link rate) is greater than Rc (router-client link rate), what is the primary constraint on the rate at which data leaves the router?
If Rs (server-router link rate) is greater than Rc (router-client link rate), what is the primary constraint on the rate at which data leaves the router?
In a scenario where Rs > Rc, what happens to the backlog of bits at the router waiting for transmission to the client?
In a scenario where Rs > Rc, what happens to the backlog of bits at the router waiting for transmission to the client?
Given a file of F bits to transfer from a server to a client, what is the approximate transfer time in a two-link network with server-router rate Rs and router-client rate Rc?
Given a file of F bits to transfer from a server to a client, what is the approximate transfer time in a two-link network with server-router rate Rs and router-client rate Rc?
What is the throughput if Rs = 10 Mbps and Rc = 5 Mbps?
What is the throughput if Rs = 10 Mbps and Rc = 5 Mbps?
Consider a network where a server is connected to a router with a link rate of 20 Mbps, and the router is connected to a client with a link rate of 15 Mbps. If the server starts sending data at its maximum rate, what is the maximum rate at which the client can receive the data?
Consider a network where a server is connected to a router with a link rate of 20 Mbps, and the router is connected to a client with a link rate of 15 Mbps. If the server starts sending data at its maximum rate, what is the maximum rate at which the client can receive the data?
Assume a file of 100 MB is being transferred from a server to a client through a router. The server-router link has a rate of 25 Mbps, and the router-client link has a rate of 20 Mbps. Approximately how long will it take to transfer the entire file?
Assume a file of 100 MB is being transferred from a server to a client through a router. The server-router link has a rate of 25 Mbps, and the router-client link has a rate of 20 Mbps. Approximately how long will it take to transfer the entire file?
In a network with multiple links between a server and a client, how does increasing the rate of a non-bottleneck link affect the overall throughput?
In a network with multiple links between a server and a client, how does increasing the rate of a non-bottleneck link affect the overall throughput?
Flashcards
Communication Links
Communication Links
Communication pathways using physical media (coaxial, copper, fiber, radio).
Transmission Rate
Transmission Rate
Rate at which data is transferred over a link, measured in bits per second.
Packets
Packets
Units of data sent across a network, containing segments of data with added headers.
Packet Switch
Packet Switch
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Link-Layer Switch
Link-Layer Switch
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Routers
Routers
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Route/Path
Route/Path
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Packet-Switched Networks
Packet-Switched Networks
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End Systems
End Systems
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Internet Service Providers (ISPs)
Internet Service Providers (ISPs)
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Upper-Tier ISPs
Upper-Tier ISPs
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Protocol
Protocol
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TCP/IP
TCP/IP
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IP (Internet Protocol)
IP (Internet Protocol)
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TCP (Transmission Control Protocol)
TCP (Transmission Control Protocol)
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Queuing Delay
Queuing Delay
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Traffic Intensity
Traffic Intensity
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Packet Loss
Packet Loss
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Queue Capacity
Queue Capacity
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End-to-End Packet Loss
End-to-End Packet Loss
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Packet Loss Probability
Packet Loss Probability
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Packet Retransmission
Packet Retransmission
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End-to-End Basis
End-to-End Basis
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DoS Attacks
DoS Attacks
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Packet Sniffer
Packet Sniffer
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Packet Sniffing
Packet Sniffing
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Wireless Network Vulnerability
Wireless Network Vulnerability
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Cable Access Technologies Vulnerability
Cable Access Technologies Vulnerability
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Throughput
Throughput
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Bottleneck Link
Bottleneck Link
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Throughput when Rs < Rc
Throughput when Rs < Rc
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Throughput when Rc < Rs
Throughput when Rc < Rs
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Backlog of Bits
Backlog of Bits
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Overall Throughput
Overall Throughput
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File Transfer Time
File Transfer Time
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Throughput Two-Link Network
Throughput Two-Link Network
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Malware
Malware
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Botnet
Botnet
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Denial-of-Service (DoS) Attack
Denial-of-Service (DoS) Attack
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Vulnerability Attack (DoS)
Vulnerability Attack (DoS)
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Bandwidth Flooding (DoS)
Bandwidth Flooding (DoS)
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Self-Replicating Malware
Self-Replicating Malware
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Spyware
Spyware
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Network Vulnerabilities
Network Vulnerabilities
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Study Notes
- Communication links consist of physical media like coaxial cable, copper wire, optical fiber, and radio spectrum.
- Different links transmit data at different rates, measured in bits/second (bps).
- Sending end systems segment data and add header bytes to each segment.
- Packets are information packages sent through the network.
- A packet switch forwards packets on outgoing communication links.
- Routers and link-layer switches are types of packet switches.
- Link-layer switches are used in access networks.
- Routers are used in the network core.
- A route or path is the sequence of links and switches traversed by a packet.
- Cisco predicts annual global IP traffic of nearly five zettabytes by 2022.
- Packet-switched networks transport packets similar to how transportation networks transport vehicles.
- Packets are analogous to trucks.
- Communication links are analogous to highways and roads.
- Packet switches are analogous to intersections.
- End systems are analogous to buildings.
- End systems access the Internet through Internet Service Providers (ISPs).
- ISPs include residential, corporate, university, WiFi, and cellular data providers.
- Each ISP is a network of packet switches and communication links.
- ISPs offer network access types like cable modem, DSL, high-speed LAN, and mobile wireless.
- ISPs also provide Internet access to content providers.
- Lower-tier ISPs interconnect through national and international upper-tier ISPs.
- Upper-tier ISPs use high-speed routers and fiber-optic links.
- Each ISP network is managed independently, runs the IP protocol, and conforms to naming/address conventions.
- End systems and packet switches run protocols to control information sending and receiving.
- Transmission Control Protocol (TCP) and Internet Protocol (IP) are important Internet protocols.
- The IP protocol specifies the format of packets.
- The Internet's protocols are known as TCP/IP.
Delay, Loss, and Throughput
- A small increase in traffic intensity can cause a much larger increase in delay.
- Queuing delays occur when traffic intensity is close to 1 and a slightly larger amount of traffic is introduced.
- When packet arrival rate is high enough that the traffic intensity exceeds 1, the queue slowly accumulates over time.
- Queuing capacity depends on router design and cost.
- A packet can be dropped if it arrives at a full queue, known as packet loss.
- Packet loss looks like a packet never emerging from the network at the destination.
- A lost packet may be retransmitted to ensure data transfer.
- Performance is measured in delay and the probability of packet loss.
- Throughput is the rate at which data is successfully transferred.
- Throughput in a two-link network is the minimum of the rates of the two links (bottleneck link).
- The time to transfer a large file of F bits is approximately F/min{Rs, Rc}.
Vulnerabilities and Attacks
- Malware can enter devices through the Internet, along with good content.
- Malware can delete files, install spyware, and collect private information.
- Compromised hosts can be enrolled in botnets for spam or DDoS attacks.
- Self-replicating malware spreads exponentially.
- Denial-of-Service (DoS) attacks render networks or hosts unusable.
- Targets of DoS attacks include web servers, e-mail servers, DNS servers, and institutional networks.
- Types of DoS attacks include:
- Vulnerability attack: Exploits vulnerabilities in applications or operating systems with crafted messages.
- Bandwidth flooding.
- Wireless Internet access creates security vulnerabilities due to potential packet sniffing.
- Packet sniffers record copies of transmitted packets.
- Sniffers can be deployed in wired LAN and cable access environments.
- Attackers who access a router or access link can plant a sniffer.
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Description
Overview of communication networks, including physical media, data transmission rates, and packet switching. Covers the roles of routers and link-layer switches in forwarding packets. Analogy between packet-switched networks and transportation networks.
