Questions and Answers
What is the primary function of the Data-Link layer in the Internet?
What type of link is characterized by two nodes being physically connected by a transmission medium?
What is the purpose of the Address Resolution Protocol (ARP)?
What are the two sublayers of the Data-Link layer?
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What type of address is used to send packets to a group of nodes on the same network?
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What is the primary purpose of Address Resolution Protocol (ARP)?
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What is the main difference between a single-bit error and a burst error?
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What is the central concept in detecting or correcting errors?
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What does error correction require?
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What determines the strength of a coding scheme?
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Study Notes
Data-Link Layer
- The Data-Link layer is responsible for node-to-node communication, controlling how data travels between two directly connected devices (nodes) in a network.
- It is located between the Physical and Network layers, providing services to the Network layer and receiving services from the Physical layer.
Nodes and Links
- A node is a device that forwards data packets, such as routers or switches.
- A link is a connection between two nodes, which can be a physical medium like a cable or air.
Services Provided by Data-Link Layer
- Framing: dividing data into frames
- Flow Control: managing data transmission rate
- Error Control: detecting and correcting errors
- Blocking Control: controlling data transmission in a link
Types of Links
- Point-to-point link: a direct connection between two nodes
- Broadcast link: a connection that allows data to be sent to multiple nodes
Sublayers of Data-Link Layer
- Data Link Control (DLC): responsible for point-to-point and broadcast links
- Media Access Control (MAC): responsible for broadcast links only
Link-Layer Addressing
- IP addresses are not enough to route packets across multiple networks, so link-layer addresses are needed to identify the path a packet takes.
- There are three types of link-layer addresses: Unicast, Multicast, and Broadcast.
- Even numbers are used for Multicast addresses.
Address Resolution Protocol (ARP)
- Used to resolve IP addresses to link-layer addresses
- When a node has an IP packet to send, it needs the link-layer address of the next node in the path
Types of Errors
- Single-bit error: one bit of data is changed from 1 to 0 or 0 to 1
- Burst error: two or more bits are changed in a data unit
Redundancy and Error Detection/Correction
- Redundancy is the central concept in detecting or correcting errors, achieved by sending extra bits with data
- Detection is easier than correction, as it only checks if an error has occurred
- Correction requires knowing the exact number of corrupted bits and their location in the message
Coding Schemes
- Redundancy is achieved through various coding schemes that create a relationship between redundant bits and data bits
- The ratio of redundant bits to data bits and the strength of the process are important factors in any coding scheme
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Description
Learn about the Data-Link Layer's role in node-to-node communication, controlling packet transfer between hosts across networks.
