Questions and Answers
What is a Computer Network?
Two or more computers that are connected with one another for the purpose of communicating data electronically and for sharing resources.
What is the role of a Source in a computer network?
A device that generates the data to be transmitted.
What does the Transmitter do?
Transforms and encodes the information that needs to be transmitted.
What is the purpose of the Transmission Medium?
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What is a Receiver in a computer network?
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What does Destination refer to in a computer network?
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A protocol is a set of rules that govern data communication.
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Which of the following layers are part of the OSI Model?
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What is the primary role of the Transport Layer?
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What does the Presentation Layer handle?
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Which of these protocols operates at the Transport Layer?
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The Data Link Layer is responsible for end-to-end communication.
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What does segmentation refer to in the context of the Transport Layer?
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The physical topology defines how devices are connected in a network and can include ______, star, ring, or bus topologies.
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What is a characteristic of circuit switching?
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What is the typical size of data packets transmitted?
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In packet switching, packets are received, buffered, and passed on to the next node.
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What is a datagram?
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Quality of service (QoS) is an issue that has been discussed more than ____ .
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Which of the following are characteristics of reliable transmission?
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Match the following traffic shaping techniques with their descriptions:
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In FIFO queuing, packets are processed based on their arrival order.
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What is starvation in priority queuing?
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What does traffic shaping aim to achieve?
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What is the purpose of TCP in the Internet protocol stack?
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UDP provides reliability, flow control, and congestion control.
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What does the network layer of the Internet do?
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What does the IP protocol define?
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What is a repeater and at what layer does it operate?
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What is the main function of a hub?
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What is the difference between a bridge and a switch?
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What does a router do?
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What is the length of an IPv4 address?
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What is a MAC address?
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What type of connection provides a dedicated link between two devices?
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What does 'DNS' stand for?
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What is a URI?
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Which protocol is used for converting an IP address to a physical address?
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What type of data transfer does unicast represent?
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What is the key characteristic of multicasting?
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Study Notes
Overview of Computer Networks
- A computer network consists of two or more interconnected computers for electronic data communication and resource sharing.
- Devices such as computers, printers, and other capable devices can be connected via communication channels.
Basics of Data Communication
- Data communication involves transmitting data from one point to another.
- Key components include source, transmitter, transmission medium, receiver, and destination.
Key Elements of the Communication Model
- Source: Generates data for transmission.
- Transmitter: Encodes and transforms information for transmission.
- Transmission Medium: Provides the pathway for communication.
- Receiver: Accepts and converts signals from the transmission medium.
- Destination: Final recipient of the data.
Role of Protocols in Networking
- Protocols are sets of rules governing data communication.
- Networks consist of complex pieces: hosts, routers, applications, protocols, hardware, and software.
Layered Network Design
- Layering allows management of complex systems and enhances modularization and maintainability.
- A change in one layer's service does not affect others, simplifying updates.
OSI Model Introduction
- The Open Systems Interconnection (OSI) model is an ISO standard for understanding network communication.
- It consists of seven layers, each with specific roles and responsibilities.
Organization of the OSI Layers
- Layer 1 (Physical Layer): Handles bit transmission over a physical medium, including interfaces and media characteristics.
- Layer 2 (Data Link Layer): Manages framing, physical addressing, flow control, error control, and access control.
- Layer 3 (Network Layer): Responsible for source-to-destination delivery across networks, involving logical addressing and routing.
- Layer 4 (Transport Layer): Ensures process-to-process message delivery, overseeing error and flow control.
- Layer 5 (Session Layer): Establishes and manages communication sessions, supporting dialog control.
- Layer 6 (Presentation Layer): Deals with data format translation, encryption, and compression.
- Layer 7 (Application Layer): Provides user access to network services, supports applications, and interfaces.
Detailed Functions of OSI Layers
- Physical Layer: Defines transmission medium, bit representation, data rate, synchronization, line configuration, physical topology, and transmission mode.
- Data Link Layer: Adds header for addressing, implements flow and error control, and manages access on shared links.
- Network Layer: Implements logical addressing for packet delivery and routing functions across interconnected networks.
- Transport Layer: Responsible for end-to-end communication, including service-point addressing, message segmentation, and connection control.
- Session Layer: Manages sessions, allowing full-duplex and half-duplex communication and adding checkpoints.
- Presentation Layer: Translates data formats, ensures encryption for privacy, and performs data compression.
- Application Layer: Interfaces with users or applications for network access and supports various services.
Internet Protocol Stack
- Mimics the OSI model with five layers, focusing on application (HTTP, FTP, SMTP), transport (TCP, UDP), network (IP), link, and physical.
- Each layer serves specific functions essential for data transmission and application support.
- TCP provides reliable, connection-oriented services, while UDP offers a faster, connectionless approach.
Communication Process in the Internet Protocol Stack
- Address resolution translates human-friendly names to IP addresses.
- Applications communicate via transport layer protocols, with IP facilitating routing of packets across networks.
Summary of OSI and Internet Protocol Functions
- Protocols at each layer work cohesively to manage data transfer, enhance reliability, and ensure effective communication across complex networks.### Internet Protocol Stack
- Protocols depend on the link and transmission medium (e.g., twisted-pair copper, fiber optics).
- Ethernet has multiple physical-layer protocols tailored for different mediums (copper, coaxial, fiber).
Network Devices
- Repeater: Operates at the physical layer, regenerates signals without amplification; two-port device.
- Hub: Multiport repeater connecting several devices; broadcasts data to all connected ports leading to inefficiencies because all devices share the same collision domain.
- Bridge: Functions at the data link layer; filters content using MAC addresses, connects two LANs running the same protocol; two-port device.
- Switch: Multiport bridge with buffering capabilities, performs error checking, routes data packets selectively to the appropriate port; operates at the data link layer.
- Router: Routes packets based on IP addresses; connects LANs and WANs, maintains a dynamic routing table; operates mainly at the network layer.
Network Identifiers
- Hostname: Unique name assigned to each device on a network; accessed via command prompt.
- IP Address: Unique logical address; IPv4 is 32 bits and permits over 4 billion addresses; IPv6 is 128 bits.
- MAC Address: Unique physical identifier for each NIC; 12-nibble, 48 bits, fixed at manufacturing.
- Port: Logical channel for data transmission; represented by 16-bit integer, totaling 65,536 ports.
- Socket: Combination of IP address and port number.
- DNS Server: Translates domain names to IP addresses; facilitates easier navigation of the Internet.
- ARP and RARP: ARP converts IP addresses to MAC addresses; RARP does the reverse.
Internet Overview
- The Internet is a vast interconnected network, governed by no single authority but overseen by organizations like ISOC and the IAB.
- Established from ARPANET in 1983; currently supports about 1 billion computers and 3.2 billion global users.
- Data on the Internet is approximately 5 million Terabytes in size, with the backbone composed of 550,000 miles of underwater cables.
Goals of Computer Networks
- Resource Sharing: Enables shared access to devices such as printers and scanners among geographically distributed computers.
- High Reliability: Provides alternate sources for data, ensuring availability even during failures.
- Inter-process Communication: Facilitates real-time interaction across geographically distant users.
- Flexible Access: Allows access to files from any network computer.
Connection Types
- Point-to-Point Connection: Provides a dedicated link between two devices for direct communication.
- Multipoint Connection: Shares a single link among multiple devices, which can either share spatially or temporally.
Transmission Modes
- Simplex Mode: Unidirectional communication where one device only sends data and the other only receives (e.g., keyboard to monitor).
- Half-Duplex Mode: Both devices can transmit and receive, but not simultaneously (e.g., walkie-talkies).
- Full-Duplex Mode: Allows simultaneous two-way communication, optimizing channel capacity (e.g., telephone conversations).
Types of Transmission Media
- Guided Media: Wired or bounded media offering high speed and security for shorter distances.
- Unguided Media: Wireless or unbounded media suitable for longer distances, but less secure.
Data Transmission Types
- Unicast: One-to-one communication between a single sender and receiver.
- Broadcast: One-to-all communication, with two types: Limited (to all devices within a network) and Direct (to all devices across networks).
- Multicast: Data sent from one or more senders to multiple recipients, striking a balance between unicast and broadcast, often requiring additional protocols like IGMP.
Packet Switching
- Circuit Switching: Resources allocated for a specific call; often results in idle connections.
- Basic Operation: Data transmitted in small packets, each containing control information alongside user data for routing.
- Advantages: Enhances line efficiency and allows for data rate conversion; packets are accepted even in busy networks.
- Transmission Handling: Packets can be treated as datagrams (independent) or through virtual circuits (established route), with differing reliability and flexibility.
Data Traffic Management
- Congestion Control: Mechanisms to prevent or manage network congestion by maintaining packet flow within capacity limits.
- Quality of Service (QoS): Aims to provide enhanced services to specific network traffic; essential for applications with varying reliability and delay sensitivity.
QoS Characteristics
- Reliability: Critical for applications like file transfers and email; less so for telephony.
- Delay: Varied tolerance among applications; minimum delay is crucial for real-time communications.
- Jitter: Variance in packet delay, more disruptive for media applications requiring consistent timing.
- Bandwidth: Different applications have distinct bandwidth requirements based on data size and frequency.
QoS Improvement Techniques
- Scheduling: Manages packets from flows fairly at switches/routers (e.g., FIFO, Priority Queuing).
- Traffic Shaping: Controls and regulates the flow of data to ensure optimal network performance.
- Resource Reservation: Allocates network resources ahead of time for critical applications.
- Admission Control: Regulates which flows can enter the network based on resource availability.### Priority Queuing
- Higher-priority packets are processed before lower-priority packets, improving Quality of Service (QoS).
- Multimedia traffic benefits significantly from reduced delays using priority queues.
- Potential issue of starvation occurs when high-priority traffic continuously monopolizes processing time, blocking lower-priority packets indefinitely.
Weighted Fair Queuing
- Weighted fair queuing allocates different weights to queues based on priority.
- Queues are processed in a round-robin manner; higher weight queues receive more packets.
- Example weights: three packets from the highest priority queue, two from the next, and one from the lowest.
- Without priority, all queues can be assigned equal weights.
Traffic Shaping
- Traffic shaping minimizes network congestion by regulating data transmission rates.
- Involves negotiation between sender and carrier regarding data flow patterns during connection setup.
- Common algorithms for traffic shaping include Leaky Bucket and Token Bucket.
Leaky Bucket Algorithm
- Controls network rate through a fixed output rate regardless of input burstiness.
- Operates like a single-server queue with constant service time, discarding packets if the bucket overflows.
- Maintains uniform packet flow by allowing one packet per clock cycle, smoothing bursts into consistent rates.
- Can be adapted for variable packet sizes by allowing a fixed number of bytes to be processed per tick.
Token Bucket Algorithm
- Allows variable output rates, accommodating bursts larger than the average rate.
- Uses tokens; one token is required to send each packet, generated at a consistent rate.
- Hosts can accumulate tokens (up to a maximum), enabling larger bursts to be sent later.
- Offers more flexibility than the Leaky Bucket, allowing for regulated yet bursty traffic.
Leaky Bucket vs Token Bucket
- In Token Bucket, packets are sent only if sufficient tokens are available, while Leaky Bucket sends packets at a constant average rate.
- Token Bucket can handle bursts more efficiently by allowing storage of tokens for future use, unlike the Leaky Bucket which does not permit any accumulation.
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Description
This quiz covers the fundamentals of advanced computer networks, including the definition of a computer network, its key elements, and the basics of data communication. Test your understanding of how devices communicate and share resources over a network.
