Chapter 7 Quiz

Networking Essentials - 8th Edition

• This is a guide to networking essentials, 8th edition, copyright 2020 Cengage. All rights reserved. Scanning, copying, or distributing this material is prohibited.

Chapter 7: Network Reference Models and Standards

• Objectives: Describe the OSI and IEEE 802 networking models and summarize IEEE 802 networking standards.

Introducing the OSI and IEEE 802 Networking Models

• The Open Systems Interconnection (OSI) reference model, proposed by the International Organization for Standardization (ISO), provides a common framework for networking developers and students.
• The OSI model isn't tied to a specific protocol suite and applies to most networking protocols.
• It structures how data travels through a network with seven layers.

Role of a Reference Model

• A layered model, like the US Postal Service, simplifies complex processes.
• Components within layers work independently, but together form the overall process.
• Changes to one layer don't necessarily affect other layers.

Role of a Reference Model (Continued)

• Individual tasks in a layered process can be handled independently.
• Modifications to one part of the process can be implemented without disrupting other parts.

Structure of the OSI Model

• A seven-layer model visually describes the flow of data.
• Layers cooperate and interact, from lowest (Physical layer) to highest (Application layer).

Structure of the OSI Model (Continued)

• Each layer has well-defined functions for network data operation.
• Layer functions interact with adjacent layers above and below it.
• TCP/IP model is referenced for comparison.

Structure of the OSI Model (Continued)

• The diagram visually compares the OSI model with the TCP/IP model.
• Each layer has its associated protocols (e.g. HTTP, TCP, IP).

Structure of the OSI Model (Continued)

• Network functions run in layers, up-and-down the protocol stack.
• Data is divided into protocol data units (PDUs).
• PDUs are passed between layers; some layers add headers to the PDU for formatting.
• De-encapsulation strips headers at the receiving end, converting the PDU to the original data.

Application Layer

• The Application layer (Layer 7) provides interfaces (e.g., file sharing, messaging) for applications to access network services.
• Client and server components exist in the Application layer.
• Common protocols include HTTP, FTP, and SMTP.

Presentation Layer

• The Presentation layer (Layer 6) handles data formatting and translation (e.g. conversion of formats).
• Handles conversion of incoming and outgoing data to/from the application layer.
• Redirects requests that can't be handled locally.

Session Layer

• The Session layer (Layer 5) governs ongoing communications, known as a session.
• It manages connections, communication setups, and communication teardown.
• Functions include name lookup, user login/logoff, and synchronization of data streams (e.g., video and audio).

Transport Layer

• The Transport layer (Layer 4) manages data transfer.
• It breaks larger data streams into smaller segments and ensures reliability through acknowledgments and resequencing.
• Uses a maximum transmission unit (MTU) and reorders segments in the correct sequence
• Important PDUs at this layer include segments and UDP datagrams.

Transport Layer (Continued)

• Data in the transport layer is divided into segments.
• The Transport layer header carries port numbers and sequencing information.
• Problems include large network segments causing performance degradation.

Network Layer

• The Network layer (Layer 3) handles logical addresses, mapping to physical addresses, and best path routing in an internetwork.
• Routers operate in the Network Layer.
• Issues include incorrect IP addresses, incorrect router configurations, and router errors.

Network Layer (Continued)

• Visual representation shows how Network layer PDUs are packet-based.

Data Link Layer

• The Data Link layer (Layer 2) is the intermediary between the Network layer and the Physical layer.
• Defines access to network medium (media access control).
• Layer 2 frames consist of headers and trailers, including CRC for error checking.
• The CRC value checks the data's integrity.

Data Link Layer (Continued)

• The Data Link layer (Layer 2) is responsible for frame error verification and processing.
• Frame headers and trailers include source and destination addresses.
• Hardware components including NICs and switches.

Physical Layer

• The Physical layer (Layer 1) converts bits into signals and vice versa.
• Transmits signals based on the network medium (wire, fiber, wireless)
• Details on connectors and the type of signals used are specified in this layer.
• Includes components such as cables, connectors, repeaters, and hubs.

Physical Layer (Continued)

• Encoding processes represent binary data as physical signals (voltage, light pulses).
• Components include cabling, connectors, repeaters, and hubs.
• Problems can exist with incorrect media terminations, electromagnetic interference, and malfunctioning NICs/hubs.

IEEE 802 Networking Standards

• These standards ensure compatibility between different network interfaces and cabling systems.
• Predate the OSI model and influence the lower layers of the model.
• Specifications describe how network interface cards (NICs) access and transfer data.

IEEE 802 Specifications (Continued)

• IEEE 802 documents are numbered (e.g., 802.3, 802.11).
• Each number often corresponds to technologies and their enhancements.

IEEE 802 Specifications (Continued)

• Different variations of Ethernet technologies are enumerated.

IEEE 802 Extensions to the OSI Model

• The two lowest OSI layers (Physical and Data Link) are further divided into sublayers (e.g., LLC and MAC) in IEEE 802 standards.
• This separation ensures logical and media access control within the network.

Chapter Summary

• OSI reference model and IEEE Project 802 provide a framework for networking, classifying functions into layers and describing media access.
• Different layers in OSI model have different functionalities.
• IEEE 802 defines network interfaces and cabling standards.

Chapter Summary (Continued)

• The IEEE 802.2 standard specifies a Logical Link Control (LLC) and Media Access Control (MAC) sublayer, improving network standardization and compatibility.