M3Q17: The OSI Model Flashcards
Module 3: Quiz 17 - The OSI Model
Which layer of the OSI Model is layer 3?
A. Data Link
B. Physical
C. Presentation
D. Network
D. Network
Explanation: Layer 3 is the Network Layer which contains functionality such as routing, protocols such as IP, and devices such as routers.
Network media such as cables and connectors reside on the Data Link Layer of the OSI Model.
A. True
B. False
B. False
Explanation: The Physical Layer (layer 1) is where all cables and media are referenced in the OSI Model. The Data Link Layer is where devices such as Switches operate.
TCP and UDP reside at this layer of the OSI Model.
A. Layer 3
B. Layer 2
C. Layer 7
D. Layer 4
D. Layer 4
Explanation: Layer 4 of the OSI Model is the Transport Layer where TCP and UDP operate.
Which layer is the Data Link Layer of the OSI Model?
A. Layer 3
B. Layer 2
C. Layer 6
D. Layer 1
B. Layer 2
Explanation: The Data Link Layer is the layer just above the Physical Layer (layer 1). The Data Links Layer is layer 2 which contains the MAC and LLC sub-layers and is where switches and MAC addresses reside.
This layer of the OSI Model is a reference point for IP routing and routers.
A. Network
B. Data Link
C. Transport
D. Presentation
A. Network
Explanation: The Network Layer is layer 3 which references logical addressing and the protocols and devices (such as routers) that make it possible to route traffic from one network to another network.
What is the protocol data unit (PDU) at layer 2 of the OSI model?
A. Packet
B. Bits
C. Data
D. Frame
D. Frame
Explanation: Frames represent encapsulation (the packaging of information) at the Data Link layer. The Frame is the last form of encapsulation before the information is placed onto the physical medium as ones and zeros.
What is the protocol data unit (PDU) at layer 3 of the OSI model?
A. Packet
B. Bits
C. Data
D. Segment
A. Packet
Explanation: When information arrives at the Network Layer (layer 3) it includes logical addressing added to it such as the source and destination IP address. When this happens we call it most commonly a Packet, such as an IP Packet. However, it can also be called a datagram if it’s a connection-less transmission.
What is the protocol data unit (PDU) at layer 4 of the OSI model?
A. Transport
B. Bits
C. Segment
D. Data
C. Segment
Explanation: When information arrives at the Transport Layer it includes port based information to define the protocol or application that the information is for. When information is referenced with a TCP port number it is called a Segment.
What is the protocol data unit (PDU) at layer 1 of the OSI model?
A. Transport
B. Bits
C. Segment
D. Data
B. Bits
Explanation: When information is ready to be placed onto the wired or wireless transmission medium it is performed by signaling a series of ons and offs similar to a flash light turning on and then off again in repetition. These ons and offs equate to ones and zeros in the world of computing and are called bits. This is the reason why we call the information bits when is it at the physical Layer of the OSI Model (layer 1).
The protocol data unit for the top three layers of the OSI Model (layers 5 – 7) is the same.
A. True
B. False
A. True
Explanation: Layer 5 – 7 of the OSI Model are the Session Layer, Presentation Layer and Application Layer respectively. These layers all have the same PDU which is simply called Data.
A Host computer works at which layer(s) of the OSI Model.
A. Layers 5-7
B. No layers
C. Layers 1-4
D. All layers
D. All layers
Explanation: Host computers run applications that access network resources. This is the entire reason why we need networks in the first place – so that an application on a computer can send data to an application on another computer. So, host computers work at the Application Layer and process information all the way down the OSI model encapsulating the Data into Segments, Packets, Frames, and then placing it onto the medium as bits via the network interface card.
