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Questions and Answers
What is the main duty of the Physical Layer in a network?
What is the main duty of the Physical Layer in a network?
To move or transport data in signal form from one device/node to another via a transmission medium.
What are some examples of transmission media that can be used in networking?
What are some examples of transmission media that can be used in networking?
Copper wire, optical fiber, or air.
What does the Data-link Layer do with the data before it reaches the Physical Layer?
What does the Data-link Layer do with the data before it reaches the Physical Layer?
Encapsulates the data into a Frame.
How is a Frame, composed of bits, transformed for transmission by the Physical Layer?
How is a Frame, composed of bits, transformed for transmission by the Physical Layer?
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Name some of the topics related to the Physical Layer in ECE courses/subjects.
Name some of the topics related to the Physical Layer in ECE courses/subjects.
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What are the two options when the buffer of the receiver Data-link layer becomes full?
What are the two options when the buffer of the receiver Data-link layer becomes full?
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What are the three main components of Error Control at the Data-link layer?
What are the three main components of Error Control at the Data-link layer?
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In what scenarios does Congestion Control typically apply?
In what scenarios does Congestion Control typically apply?
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What are the two ways the Data-link layer controls the utilization of the transmission medium?
What are the two ways the Data-link layer controls the utilization of the transmission medium?
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Differentiate between Point-to-point and Broadcast links in terms of capacity usage and device connectivity.
Differentiate between Point-to-point and Broadcast links in terms of capacity usage and device connectivity.
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Study Notes
Flow Control
- Flow control is used to manage the rate of producing and consuming frames to prevent buffer overflow.
- When the buffer is full, two options are available:
- Excess frames are automatically dropped.
- The data-link layer sends feedback to the sending/source data-link layer to ask it to stop or slow down.
Error Control
- Error control involves:
- Detection
- Correction
- Discard and retransmission
- Electromagnetic signals are susceptible to errors due to EMI, crosstalk, etc., which affect the integrity of the frame.
Categories of Links
- There are two ways the data-link layer controls the way transmission medium is used:
- Point-to-point link
- Broadcast link
- Point-to-point link:
- The data-link layer uses the whole capacity of the transmission medium.
- The link is dedicated to the two connecting devices/hosts.
- Examples: Bluetooth, remote control, microwave link, satellite link.
- Broadcast link:
- The data-link layer uses only a part of the capacity of the link.
- The link is shared among several pairs of devices.
- Examples: Wi-Fi, cellular service, radio/tv stations.
The Link Layer
- The Link Layer is also called the Network Interface Layer or Network Access Layer.
- It is composed of the Physical and Data-link layers.
- The Link Layer is the group of methods and communications protocols confined to the link that a host is physically connected to.
The Duty and Scope of the Physical Layer
- The duty of the Physical Layer is to move or transport data in signal form from one device/node to another via a transmission medium.
- The transmission medium can be copper wire, optical fiber, or air.
- The data can be texts, numbers, images, audio, or video encapsulated into a Frame at the Data-link Layer.
Nodes and Links
- Nodes are hosts and routers.
- Links are the connecting networks in between.
- Data-link Layer logical connection is Node-to-Node.
- Data units from the source host to the destination host in the Internet pass through multiple nodes and links.
Duty Scope of the Data-Link Layer
- The Data-Link Layer provides services to the Network Layer.
- Its duty is node-to-node, hop-to-hop, link-to-link (not end-to-end).
- It is responsible for the delivery of a Datagram from one node to the next.
- The Data-Link layer of the sending node encapsulates the Datagram from the Network layer to become a Frame.
- The Data-Link layer of the receiving node decapsulates the Datagram from the Frame.
Data-Link Layer Services
- The Data-Link Layer services are:
- Framing
- Flow Control
- Error Control
- Congestion Control
Framing
- Framing is the first service of the Data-Link Layer.
- At each node, the Datagram has to be encapsulated in a Frame before sending it to the next node.
- The node also has to decapsulate the Datagram from the Frame received on the logical channel.
- A Frame has a header and a trailer.
- The framing formats are dictated by the Data-link layer standard being implemented, e.g., Ethernet.
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Description
Test your knowledge on the composition of the Link Layer and the services of the Physical Layer in data communications. This quiz covers topics from Module 3.1 Week 7 lectures by ENGR.J.E.T.TENAZAS at the Electronics Engineering Department, Technological Institute of the Philippines - Quezon City.
