OSI Model Layers and Functions

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At which of the following layers of the Open Systems Interconnection (OSI) model do the protocols on a typical local area network (LAN) use media access control (MAC) addresses to identify other computers on the network?

  • Network
  • Physical
  • Transport
  • Data link (correct)

Which of the following organizations developed the Open Systems Interconnection (OSI) model?

  • American National Standards Institute (ANSI)
  • International Organization for Standardization (ISO) (correct)
  • International Telecommunication Union (ITU-T)
  • Institute of Electrical and Electronics Engineers (IEEE)
  • Comité Consultatif International Télégraphique et Téléphonique (CCITT)

Which layer of the Open Systems Interconnection (OSI) model is responsible for the logical addressing of end systems and the routing of datagrams on a network?

  • Application
  • Network (correct)
  • Physical
  • Presentation
  • Session
  • Transport
  • Data link

On a TCP/IP network, which layers of the Open Systems Interconnection (OSI) model contain protocols that are responsible for encapsulating the data generated by an application, creating the payload for a packet that will be transmitted over a network? (Choose all that apply.)

<p>Presentation (C), Transport (G)</p> Signup and view all the answers

Which layer of the Open Systems Interconnection (OSI) model is responsible for translating and formatting information?

<p>Presentation (C)</p> Signup and view all the answers

Which of the following devices typically operates at the Network layer of the Open Systems Interconnection (OSI) model?

<p>Router (B)</p> Signup and view all the answers

Which layer of the Open Systems Interconnection (OSI) model provides an entrance point to the protocol stack for applications?

<p>Application (F)</p> Signup and view all the answers

Which layer of the Open Systems Interconnection (OSI) model is responsible for dialogue control between two communicating end systems?

<p>Session (F)</p> Signup and view all the answers

Some switches can perform functions associated with two layers of the Open Systems Interconnection (OSI) model. Which two of the following layers are often associated with network switching? (Choose all that apply.)

<p>Physical (C), Data link (F)</p> Signup and view all the answers

At which layer of the Open Systems Interconnection (OSI) model are there TCP/IP protocols that can provide either connectionless or connection-oriented services to applications?

<p>Transport (B)</p> Signup and view all the answers

Which of the following layers of the Open Systems Interconnection (OSI) model typically have dedicated physical hardware devices associated with them? (Choose all that apply.)

<p>Data link (B), Physical (D)</p> Signup and view all the answers

At which layer of the Open Systems Interconnection (OSI) model is there a protocol that adds both a header and a footer to the information that is passed down from an upper layer, thus creating a frame?

<p>Data link (G)</p> Signup and view all the answers

Identify the layer of the Open Systems Interconnection (OSI) model that controls the addressing, transmission, and reception of Ethernet frames, and also identify the media access control method that Ethernet uses.

<p>Data link layer: CSMA/CD (C)</p> Signup and view all the answers

At which layer of the OSI model do you find the protocol responsible for the delivery of data to its ultimate destination on an internetwork?

<p>Network (A)</p> Signup and view all the answers

Which of the following is not a protocol operating at the Network layer of the OSI model?

<p>IMAP (C)</p> Signup and view all the answers

Ed is a software developer who has been given the task of creating an application that requires guaranteed delivery of information between end systems. At which layer of the Open Systems Interconnection (OSI) model does the protocol that provides the guaranteed delivery run, and what type of protocol must Ed use?

<p>Transport layer; connection-oriented (B)</p> Signup and view all the answers

Alice is a network administrator designing a new local area network (LAN). She needs to determine the type of cabling and the network topology to implement. Which layers of the Open Systems Interconnection (OSI) model apply to cabling and topology elements?

<p>Physical and Data link layers (B)</p> Signup and view all the answers

Which layers of the Open Systems Interconnection (OSI) model do not have protocols in the TCP/IP suite exclusively dedicated to them? (Choose all that apply.)

<p>Session (A), Data link (C), Application (E), Presentation (F), Physical (G)</p> Signup and view all the answers

The protocols at which layer of the Open Systems Interconnection (OSI) model use port numbers to identify the applications that are the source and the destination of the data in the packets?

<p>Transport (C)</p> Signup and view all the answers

Which of the following is a correct listing of the Open Systems Interconnection (OSI) model layers, in order, from top to bottom?

<p>Application, Presentation, Session, Transport, Network, Data link, Physical (E)</p> Signup and view all the answers

At which of the Open Systems Interconnection (OSI) model layers do switches and bridges perform their basic functions?

<p>Data link (C)</p> Signup and view all the answers

On a TCP/IP network, flow control is a function implemented in protocols operating at which layer of the Open Systems Interconnection (OSI) model?

<p>Transport (C)</p> Signup and view all the answers

Which layer of the Open Systems Interconnection (OSI) model defines the medium, network interfaces, connecting hardware, and signaling methods used on a network?

<p>Physical (E)</p> Signup and view all the answers

Which of the OSI model layers is responsible for syntax translation and compression or encryption?

<p>Presentation (D)</p> Signup and view all the answers

Which layer of the Open Systems Interconnection (OSI) model is responsible for transmitting signals over the network medium?

<p>Physical (F)</p> Signup and view all the answers

Specify the layer of the Open Systems Interconnection (OSI) model at which the Internet Protocol (IP) operates and whether it is connection-oriented or connectionless.

<p>Network; connectionless (A)</p> Signup and view all the answers

An Ethernet network interface adapter provides functions that span which two layers of the Open Systems Interconnection (OSI) model?

<p>Physical and Data link (C)</p> Signup and view all the answers

Which of the following protocols operate at the Application layer of the Open Systems Interconnection (OSI) model? (Choose all that apply.)

<p>SNMP (B), HTTP (D)</p> Signup and view all the answers

Which layer of the Open Systems Interconnection (OSI) model would be responsible for converting a text file encoded using EBCDIC on the sending system into ASCII code, when required by the receiving system?

<p>Presentation (D)</p> Signup and view all the answers

Which of the following protocols operates at the Network layer of the OSI model but does not encapsulate data generated by an upper layer protocol for transmission over the network?

<p>ARP (B)</p> Signup and view all the answers

Which of the following devices run exclusively at the Physical layer of the Open Systems Interconnection (OSI) model? (Choose all that apply.)

<p>Hubs (A), Repeaters (B)</p> Signup and view all the answers

Which of the following devices enables two computers to communicate when they are using different protocols at each layer of the Open Systems Interconnection (OSI) reference model?

<p>A router (B)</p> Signup and view all the answers

Which of the following best describes the function of a firewall?

<p>A device located between two networks that enables administrators to restrict incoming and outgoing traffic (D)</p> Signup and view all the answers

Which of the following terms is used to describe the method by which a firewall examines the port numbers in Transport layer protocol headers?

<p>Service-dependent filtering (B)</p> Signup and view all the answers

Which of the following physical network devices can conceivably be implemented as software in a computer's operating system? (Choose all that apply.)

<p>Switch (A), Firewall (B), Router (D)</p> Signup and view all the answers

Which of the following criteria does a firewall capable of service-dependent filtering use to block traffic?

<p>Port numbers (B)</p> Signup and view all the answers

Ralph is a freelance network consultant installing a three-node small business network. The computers are all in the same room and use wired Ethernet to connect to the switched ports of a multifunction device. The device also functions as a network address translation (NAT) router for a cable modem connection to the Internet. NAT provides a measure of security, but Ralph wants to be sure that the network is protected from unauthorized Internet traffic and attacks against open ports. Which of the following solutions would enable Ralph to accomplish this goal with the minimum cost to the client?

<p>Install a personal firewall on each of the computers. (C)</p> Signup and view all the answers

Which of the following statements about hubs and switches are true? (Choose all that apply.)

<p>There are switches available with Network layer functionality, but there are no hubs with that capability. (A), All of the devices connected to a hub are part of a single collision domain, whereas each device connected to a switch has its own collision domain. (B), Switches create a separate broadcast domain for each connected device, whereas hubs create a single broadcast domain for all of the connected devices. (D)</p> Signup and view all the answers

Which of the following devices perform essentially the same function? (Choose two.)

<p>Bridges (C), Switches (D)</p> Signup and view all the answers

Which of the following switch types immediately forwards frames after looking at only the destination address?

<p>Cut-through (C)</p> Signup and view all the answers

Which of the following is something that only a firewall capable of stateful packet inspection can do?

<p>Track the state of ongoing connections to prevent unauthorized connections (D)</p> Signup and view all the answers

Flashcards

OSI model layer for MAC addresses

Data Link layer

Developer of the OSI model

International Organization for Standardization (ISO)

OSI layer for logical addressing & routing

Network layer

OSI layers for data encapsulation (TCP/IP)

Transport, Session, Presentation, Application

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OSI layer for translation & formatting

Presentation layer

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Network layer device

Router

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OSI layer for application entrance

Application layer

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OSI layer for dialogue control

Session layer

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OSI layers used in switching

Physical, Data Link

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OSI layer for connection-oriented/less services

Transport layer

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OSI layers with dedicated hardware

Physical, Data Link

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OSI layer creating frames

Data Link layer

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Ethernet's data link layer protocol

CSMA/CD

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OSI layer for ultimate destination

Network layer

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Non-Network layer protocol

IMAP

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OSI layer for guaranteed delivery

Transport layer

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OSI layers for cabling/topology

Physical and Data Link

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OSI layers without direct TCP/IP protocols

Physical, Data Link, Session, Presentation

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OSI layer for application identification

Transport layer

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Correct order of OSI layers (top to bottom)

Application, Presentation, Session, Transport, Network, Data Link, Physical

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OSI layers used by switches/bridges

Data Link

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OSI layer for flow control

Transport layer

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OSI layer defining network medium

Physical layer

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OSI layer for syntax translation

Presentation layer

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OSI layer for transmitting signals

Physical layer

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IP's OSI layer and type

Network layer; connectionless

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OSI layers covered by Ethernet adapter

Physical and Data Link

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Application layer protocols

HTTP, SNMP

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OSI layer for character code conversion

Presentation layer

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Network layer protocol (no upper layer encapsulation)

ICMP

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Physical layer devices

Repeaters, Hubs

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Device for different protocol communication

Gateway

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Firewall function

Restricting network traffic (incoming and outgoing)

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Firewall method using port numbers

Service-dependent filtering

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Implementable network device as software

Firewall

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Firewall criteria for service-dependent filtering

Protocol identifiers and port numbers

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MAC addresses on LANs

MAC addresses are used to identify specific computers on a local area network (LAN). This process occurs at the Data Link layer of the OSI model, where protocols handle physical addressing.

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OSI Model Creator

The Open Systems Interconnection (OSI) model was developed by the International Organization for Standardization (ISO).

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TCP/IP Encapsulation Layers

The Transport, Session, Presentation, and Application layers in the OSI model are responsible for encapsulating data generated by applications before transmission over a network. These layers build the payload for a packet.

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OSI Layers in Network Switching

The Physical and Data Link layers of the OSI model are involved in network switching. The Physical layer handles the transfer of data on the physical network, while the Data Link layer manages physical addressing and error control.

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Connection-Oriented or Connectionless Services

The Transport layer of the OSI model provides services to applications for reliable data transfer. It can offer both connection-oriented and connectionless services depending on the needs of the application.

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Flow Control in TCP/IP

Flow control, a mechanism for managing the flow of data between devices, is primarily implemented at the Transport layer of the OSI model in TCP/IP networks.

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Study Notes

OSI Model Layers and Functions

  • Layer 1 (Physical): This layer deals with the physical transmission of data, such as cabling and signal methods. Dedicated physical hardware like repeaters and hubs operate at this layer.
  • Layer 2 (Data Link): This layer handles MAC addresses and media access control (e.g., CSMA/CD, CSMA/CA). Switches and bridges function at this layer, creating separate collision domains for connected devices. Ethernet frames use this layer. Protocols for packet delivery to the destination on an internetwork operate at this level.
  • Layer 3 (Network): This layer deals with logical addressing and routing of datagrams across a network. Protocols like IP, ICMP, and IGMP operate at this level; however, UDP does not encapsulate data from higher layers for network transmission at this level. Network layer appliances (routers) connect different networks. Flow control happens at this level. The protocol that provides delivery of data across an internetwork is in this layer.
  • Layer 4 (Transport): This layer provides connection-oriented (like TCP) or connectionless services (like UDP) to applications, including flow control. This determines the manner of transmission. Protocols are responsible for end-system dialogue communication, establishing a two-way communication protocol or enabling the exchange of information. Issues of data formatting and translation are handled at this level. Transport layer protocols operate at this layer of the OSI model.
  • Layer 5 (Session): This layer manages connection and session establishment, maintaining communication channels between applications.
  • Layer 6 (Presentation): This layer handles data translation, formatting, and encryption/decryption for applications. If an application requires encoding conversion or protocol translation for data interchange, this layer does the conversion.
  • Layer 7 (Application): This layer provides interfaces for applications to access network services. The Application layer’s protocols handle user-level activities like port numbers and application access to the network. Examples of protocols are HTTP, SNMP, and others.

Miscellaneous OSI Model Details

  • Multifunction devices: Multifunction devices can act as a combination of network devices such as routers and switches all in one box, as well as acting as a network address translator.
  • Firewall functions: Firewalls are devices that control network traffic between different networks by restricting incoming and outgoing traffic. One type capable of stateful packet inspection can determine whether a packet has a valid return from a specific service.
  • OSI Model Tools: Switches and bridges perform basic functions at the data link layer of the OSI model. Hubs operate at the Physical layer.
  • Protocols: Protocols for an internetwork are commonly located at the Network layer, although some protocols are at other layers. Protocols responsible for guaranteed delivery are from the Transport layer and are connection-oriented.
  • Network Addressing: Identifying network addresses is a significant function at the network layer. Several key entities for network addressing are on this layer.
  • Data Translation and Formatting: The Presentation layer of the OSI model is responsible for data translation, formatting, and encryption/decryption. Data conversion happens at this layer to accommodate differences in encoding schemes that different applications or systems may employ.
  • Network Medium and Connectivity: The Physical layer deals mainly with the physical network medium (the ways that signals pass from one node to another) and provides hardware such as repeaters for this task. This layer also includes network topology.
  • Network Security and Intrusion Prevention: Network intrusion prevention systems (IPS) are employed to detect threats that may bypass other security measures and prevent that traffic.

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