Introduction to Data-Link Layer

The process of adding a frame header and trailer around a network layer datagram for transmission across a network link.

The process of removing the frame header and trailer from a datagram received over a network link.

A data-link layer protocol is used to transfer data between nodes on a single network link.

The data-link layer uses specific addresses for devices on a link. Each link can have different addresses.

The data-link layer encapsulates a network layer datagram into a frame by adding frame headers and trailers before transmitting the datagram on a network link.

Each intermediate node in the network path receives a frame, decapsulates the datagram from the frame, then encapsulates the datagram into a new frame, and transmits the frame to the next node.

The destination node receives the final frame, decapsulates the datagram, and passes it up to the network layer.

The reason for encapsulation and decapsulation at each intermediate node is that each network link can use different protocols with different frame formats. Even if the same protocol is used, different link-layer addresses may be used.

The data-link layer is responsible for encapsulating a datagram from the network layer into a frame before sending it to the next node. It also decapsulates the datagram from the frame upon receiving it.

The data-link layer works at both the source and destination hosts, as well as at intermediate routers, encapsulating and decapsulating datagrams to send them across physical links.

A frame is a unit of data at the data-link layer. It contains a datagram from the network layer, along with a header and possibly a trailer for control information.

This is the process of adding header and sometimes a trailer to a datagram to create a frame. It is done by the source's data-link layer.

This is the process of removing the header and trailer from a frame to extract the datagram. This is done by the destination's data-link layer.

A physical link is a direct connection between two devices. For example, a cable connecting a router to a computer or a wireless connection.

The data-link layer uses a logical link to transmit frames between nodes. The logical link is defined by the data-link layer protocol and may not correspond directly to a single physical link.

A single router can have multiple data-link layers because it is connected to multiple physical links. Each link requires a separate data-link layer to handle the communication.

A link-layer address designed for one-to-one communication within a specific network link. Each host or router interface has a unique unicast address.

A link-layer address that enables one-to-many communication within a specific network link. It's like sending a message to a group of people on the same network.

A link-layer address used for broadcasting messages to every device on a specific network link. It's like shouting a message to everyone in the same room.

A protocol that translates IP addresses (network layer) into physical link-layer addresses (MAC addresses) to enable communication between devices on a shared network.

A method where a host or router sends a broadcast ARP request to find the MAC address of a device with a specific IP address.

A response to an ARP request containing the target device's MAC address, enabling the sender to establish a direct connection.

A table that stores mappings of IP addresses to MAC addresses, assisting a device in resolving physical addresses for subsequent communication.

A process where a host or router sends a broadcast ARP request to update its ARP cache with the MAC address associated with a specific IP address.

A device on a network, such as a computer, router, or switch, that can send and receive data.

A physical connection between two nodes on a network, allowing data to flow.

The layer of the network model responsible for delivering data frames between nodes on a single network link. It handles tasks like packetization, error control, and flow control.

A network connection that allows data to be sent to all devices on the network simultaneously.

A network connection that allows data to be sent directly between two specific devices.

The end-to-end address is the address of the destination computer, which is typically an IP address. In this scenario, the end-to-end address would be the IP address of the computer at Chicago Airport.

The link-layer address is the address that is used to identify devices on a specific network segment. In this scenario, the link-layer address would be the MAC address of the computer at Los Angeles Airport.

When Alice has to change flights in Denver, the end-to-end address remains the same, which is the IP address of the computer at Chicago Airport. However, the link-layer address changes at each step, reflecting the different networks she traverses.

Yes, the post office uses an end-to-end address to deliver letters, which is the recipient's full address. The end-to-end address is used to route the letter through various postal facilities until it reaches the destination.

Alice can still communicate with Bob, but the data will have to be routed through other devices. The data will be encapsulated into different frames at each intermediate node, and the link-layer addresses in the frames will change accordingly. This highlights the flexibility and robustness of network communication.

A network protocol used to find the physical address of a device by its IP address. It works by broadcasting a request to all devices on a network.

A mechanism for a network to send large amounts of data in smaller chunks. Data is split into multiple datagrams to be transmitted independently. This improves efficiency and reliability.

When using ARP, the sending device (System A) sends a broadcast request asking for the physical address of the receiving device (System B). Only System B responds with its physical address.

The sender device caches the physical address of the receiver device in its memory after receiving the ARP response. This allows for faster communication in subsequent data transmissions.

ARP improves network efficiency by reducing the number of broadcasts required. Sending datagrams directly to the receiver's physical address eliminates unnecessary broadcasts to other devices.

Instead of multiple broadcasts (for ARP requests), one broadcast frame (ARP request) is sent, followed by unicast frames for data transmission. This reduces network traffic.

ARP packets are encapsulated directly into data-link frames. These frames have a specific field indicating that the payload belong to ARP rather than a network-layer datagram.

The hardware type field in an ARP packet identifies the type of link-layer protocol being used. The protocol type field indicates the network-layer protocol being used.