Computer Networks Chapter 1 Quiz

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Questions and Answers

What characterizes the Internet as a network?

It is a network of interconnected networks. (correct)

It connects only personal computers.

It is limited to a specific geographic region.

It functions solely through wireless connections.

Which component is primarily responsible for directing packets through the Internet?

End systems.

Communication links.

Internet Service Providers.

Packet switches. (correct)

What is the term used to describe the path a packet takes through the network?

Communication trajectory.

Transmission route.

Route or path. (correct)

Network topology.

Which of the following best describes packet switches?

They forward packets from one link to another but do not process the packet content. Signup and view all the answers

What was the estimated number of devices connected to the Internet by 2017?

18 billion. Signup and view all the answers

What is the primary measurement of a link's transmission speed?

Bits per second (bps). Signup and view all the answers

How do end systems connect to the Internet?

Through Internet Service Providers (ISPs). Signup and view all the answers

What are the two prominent types of packet switches used in the Internet?

Routers and link-layer switches. Signup and view all the answers

What best describes guided media?

Waves are guided along a solid medium. Signup and view all the answers

What is the primary function of store-and-forward transmission in packet switching?

To receive an entire packet before transmission. Signup and view all the answers

How is the delay for sending a packet from source to destination calculated?

$rac{N imes L}{R}$ Signup and view all the answers

What determines the occurrence of packet loss in a network?

Insufficient buffer space. Signup and view all the answers

Which statement about forwarding tables is correct?

They help routers determine the next link for packet forwarding. Signup and view all the answers

What role does queuing delay play in packet switching?

It is dependent on the congestion level in the network. Signup and view all the answers

What characteristic is unique to unguided media?

It allows waves to propagate freely through the atmosphere. Signup and view all the answers

In packet-switched networks, what does each packet header primarily contain?

The destination's IP address and other routing information. Signup and view all the answers

What typically constrains throughput in modern Internet communications?

Access network limitations Signup and view all the answers

If the rate of the common link is comparatively low against the server and client rates, what becomes the bottleneck?

Shared link in the core Signup and view all the answers

What is the throughput of each download if $R_s = 2 Mbps$, $R_c = 1 Mbps$, and $R = 5 Mbps$?

500 kbps Signup and view all the answers

In a layered architecture of network design, what is the primary benefit of modularity?

Easier modification of service implementations Signup and view all the answers

What is the role of a protocol layer in network design?

To offer services by using resources from underlying layers Signup and view all the answers

When measuring throughput in a network with multiple downloads, which rate is most likely to limit performance?

The common link's transmission rate Signup and view all the answers

What is a primary characteristic of layered architecture in network systems?

Certain layers may depend directly on the functionalities of other specific layers Signup and view all the answers

How can a protocol layer be implemented in the network?

Via a combination of both software and hardware Signup and view all the answers

What is one major drawback of circuit-switched networks?

They require dedicated resources that can lead to idle periods. Signup and view all the answers

Which multiplexing method reserves time slots for conveying data in circuit-switched networks?

Time-division multiplexing (TDM) Signup and view all the answers

What is the total time required to send a file of 640,000 bits over a circuit-switched network with TDM using 24 slots and a bit rate of 1.536 Mbps?

10.5 seconds Signup and view all the answers

In circuit-switched networks, what happens when two hosts want to communicate?

A dedicated end-to-end connection is established. Signup and view all the answers

How are the forwarding tables in routers initially set up?

Through automated special routing protocols. Signup and view all the answers

Which of the following is true about the packet delivery method used by the Internet?

It makes its best effort to deliver packets but lacks guarantees. Signup and view all the answers

What type of multiplexing is demonstrated by FM radio stations sharing frequency bands?

Frequency-division multiplexing (FDM) Signup and view all the answers

Why is establishing end-to-end circuits in circuit-switched networks considered complicated?

It needs complex signaling software to coordinate switches. Signup and view all the answers

What is the correct formula for calculating nodal delay?

$d_{nodal} = d_{proc} + d_{queue} + d_{trans} + d_{prop}$ Signup and view all the answers

Which component of nodal delay is often negligible but can impact maximum throughput?

Processing delay Signup and view all the answers

What happens to the queuing delay when the traffic intensity $L_a/R$ exceeds 1?

Queuing delay approaches infinity Signup and view all the answers

In which scenario will packets experience no queuing delay?

When packets arrive periodically and the queue is empty Signup and view all the answers

Which factor does not influence queuing delay?

Geographical distance Signup and view all the answers

What is the primary impact of propagation delay in a local area network (LAN)?

Propagation delay is minimal and often negligible Signup and view all the answers

Which statement about queuing delay is TRUE?

Queuing delay can vary based on the nature of traffic arrival Signup and view all the answers

What metric defines the amount of data that can be transmitted per second between end systems?

Throughput Signup and view all the answers

What is the primary function of the transport layer in a networking model?

Transport application-layer messages between application endpoints Signup and view all the answers

Which of the following statements about the physical layer is true?

It moves individual bits within the frame based on the transmission medium. Signup and view all the answers

What drawback can occur due to protocol layering in networking?

Some layers may need access to information not contained within their own scope. Signup and view all the answers

What distinguishes TCP from UDP in transport-layer protocols?

TCP includes flow control and congestion control features, whereas UDP does not. Signup and view all the answers

What are link-layer packets referred to as in networking?

Frames Signup and view all the answers

Which layer is responsible for the delivery of datagrams to the next node along the route?

Link layer Signup and view all the answers

Which of the following protocols operates at the application layer?

HTTP Signup and view all the answers

In terms of implementation, how is the network layer typically structured?

A combination of hardware and software Signup and view all the answers

Study Notes

Introduction to Computer Networks

The Internet is a network of networks.
Students will study the public Internet as a basis for understanding computer networks and their protocols.
The course textbook is Computer Networking: A Top-Down Approach, 8th ed., by Kurose & Ross.

Course Outline

Grading: Attendance and participation (5-7%), Assignments and quizzes (40%), Midterm (15%), Final (40%)
Join the course using the code: 142tcab
Course materials and discussions are on MS Teams.
Teaching Assistant (TA): Eng. Mohamed Essam

Chapter 1: Computer Networks and the Internet

Outline: What Is the Internet?, The Network Edge, The Network Core, Delay, Loss, and Throughput in Packet-Switched Networks, Protocol Layers and Their Service Models

What Is the Internet?

The Internet is a computer network connecting billions of devices worldwide (hosts/end systems).
Estimates indicate approximately 18 billion devices in 2017 and projected to reach 28.5 billion by 2022.

A Nuts-and-Bolts Description

End systems are connected by communication links and packet switches.
Packet switches take incoming packets and forward them to outgoing links.

A Nuts-and-Bolts Description (2/3)

Transmission rates are measured in bits per second (bps).
Common packet switches are routers and link-layer switches.
A route or path is the sequence of communication links and switches traversed by a packet.
End systems access the Internet via Internet Service Providers (ISPs).
Each ISP consists of a network of packet switches and communication links.

A Nuts-and-Bolts Description (3/3)

End systems, packet switches, and other pieces of the Internet run protocols.
TCP (Transmission Control Protocol) and IP (Internet Protocol) are critical protocols.
The combined protocols are known as TCP/IP.
The Internet Engineering Task Force (IETF) develops Internet standards called Requests for Comments (RFCs).
There are nearly 9000 RFCs currently.

End Systems

The Internet's end systems include desktop computers, Macs, Linux boxes, servers (web, email), mobile devices (laptops, smartphones).
End systems also host application programs and are often categorized as clients or servers.
Many servers reside in large data centers (e.g., Google has 19 data centers globally, containing millions of servers).

Access Networks

Home Access: DSL, Cable, FTTH, and 5G fixed wireless.
Enterprise/Home Access: Ethernet and WiFi.
Wide-Area Wireless Access: 3G, LTE 4G, 5G.

Example

Example 1: Determining time required to send a file on a circuit-switched network with TDM
Example 2: Calculating the number of simultaneous users supported on a 1 Mbps link with users active 10% of the time.
Example 3: Determining the time for data transmission using shared bandwidth (TDM) under specific conditions.
Example 4: Understanding throughput considerations when multiple users or downloads utilize resources within a shared network.

Protocol Layers

The internet has layered architecture to manage the complexity of its various components (applications, protocols, end systems, packet switches, and link-level media).
Layers provide services by acting on information from directly beneath, with modularity for changes without affecting others.

Layered Structure

Details of protocols, how they interact, and what information/data exchanged are organized here.

Network Protocols

Protocols set the norms for message formats, order of messages, and actions taken when messages are exchanged/processed.

Circuit Switching

Traditional telephone networks are circuit-switched networks.
For communication, dedicated resources (buffers, link transmission rates) are reserved for the duration of the session.
A network establishes an end-to-end connection for consistent throughput.
In contrast, the Internet is a best-effort system for packet delivery.

Multiplexing in Circuit-Switched Networks

Circuits in a link can be implemented using Frequency-Division Multiplexing (FDM) or Time-Division Multiplexing (TDM), each with different mechanics.

Delay, Loss, and Throughput in Packet-Switched Networks

Physical laws create delay and loss while limiting throughput.
Delay occurs in processing, queuing, transmission, and propagation stages.
Packet loss occurs due to finite buffer sizes in switches, if a queue capacity is exceeded

Nodal Delay

Nodal delay components can vary greatly based on the network's structure (e.g., a LAN or a satellite network).
Packet handling (processing) delays can be negligible in certain configurations; however, they impact a router's maximum throughput.

Queuing Delay

The arrival rates of traffic, link rates, and burst characteristics impact queuing delays.
The intensity of traffic ( La/R ) plays a crucial role in queuing delay, with a value exceeding 1 typically resulting in uncontrolled queues and unbounded delays.

Throughput

Throughput represents the rate at which data is transmitted.
In simple scenarios, throughput is equal to the lowest transmission rate along a network path.
Other factors, including traffic and access networks, also influence throughput.

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Description

Test your understanding of the key concepts introduced in Chapter 1 of 'Computer Networking: A Top-Down Approach'. This quiz covers topics such as the Internet, network edge, network core, and packet-switched networks. Challenge yourself and see how well you grasp the foundational knowledge of computer networks.