Which two functions are performed at the MAC sublayer of the OSI Data Link Layer to facilitate Ethernet communication? (Choose two.)

In the context of Ethernet communication, the MAC (Media Access Control) sublayer of the OSI Data Link Layer performs several crucial functions. Among these, the two functions that are most relevant to your query are:

1. Places information in the Ethernet frame that identifies which network layer protocol is being encapsulated by the frame: This function involves adding a type field to the Ethernet frame. This type field indicates the network layer protocol that the frame is carrying, such as IPv4, IPv6, ARP, etc. This allows the receiving device to understand how to process the encapsulated data.
2. Adds Ethernet control information to network protocol data: This involves the encapsulation process where Ethernet-specific headers and trailers are added to the network layer data. This Ethernet header includes source and destination MAC addresses and other control information, while the trailer typically contains a Frame Check Sequence (FCS) for error detection.

The other options you mentioned, such as “handles communication between upper layer networking software and Ethernet NIC hardware” and “applies delimiting of Ethernet frame fields to synchronize communication between nodes,” are not specifically functions of the MAC sublayer in the context of Ethernet. The MAC sublayer is more focused on frame formatting, addressing, and error checking. The synchronization of communication is more of a function of the Physical layer. The communication between upper layer networking software and Ethernet hardware is an overarching function of the entire Data Link layer and the network stack, not just the MAC sublayer.

or Ethernet communication, the MAC (Media Access Control) sublayer of the OSI Data Link Layer primarily performs functions related to framing and addressing of data packets. Based on the options provided, the two functions performed at the MAC sublayer are:

1. Adds Ethernet control information to network protocol data: This function involves the process of framing, where Ethernet headers and trailers are added to network layer data. The Ethernet header typically includes source and destination MAC addresses, which are crucial for the framing and addressing of packets on a network. The trailer usually contains a Frame Check Sequence (FCS) for error detection.
2. Implements CSMA/CD over legacy shared half-duplex media: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) is a network control protocol that was used in early Ethernet technology on shared, half-duplex channels. It is designed to minimize collisions by first checking if the channel is free before transmitting data. If a collision is detected, it employs algorithms to reschedule the transmission. This function is a key aspect of the MAC sublayer in managing access to the physical medium in traditional Ethernet environments.

The other options, such as “integrates Layer 2 flows between 10 Gigabit Ethernet over fiber and 1 Gigabit Ethernet over copper,” and “enables IPv4 and IPv6 to utilize the same physical medium,” are more related to overall network design and the functionality of network devices rather than specific functions of the MAC sublayer. Similarly, “handles communication between upper layer networking software and Ethernet NIC hardware” is more of a general description of the Data Link layer’s role rather than a specific function of the MAC sublayer.

In the context of Ethernet communication within the MAC (Media Access Control) sublayer of the OSI Data Link Layer, the two functions among those listed are:

1. Implements trailer with frame check sequence for error detection: This is a key function of the MAC sublayer. The Frame Check Sequence (FCS) is a part of the Ethernet frame trailer used for error detection. It ensures the integrity of data by enabling the receiving end to detect any corruption of data that might have occurred during transmission.
2. Adds Ethernet control information to network protocol data: This involves the encapsulation process where the MAC sublayer adds Ethernet-specific headers (and trailers, including the FCS mentioned above) to the data received from the network layer. This Ethernet header typically includes source and destination MAC addresses and is essential for proper framing and addressing within an Ethernet network.

The other options, such as “handles communication between upper layer networking software and Ethernet NIC hardware” and “places information in the Ethernet frame that identifies which network layer protocol is being encapsulated by the frame,” while relevant to the overall functioning of Ethernet communication, are not specifically functions of the MAC sublayer. The MAC sublayer’s main focus is on addressing and framing of the data for Ethernet networks, along with error checking. The delineation of fields within an Ethernet frame is part of the general framing process, but is not as distinctly a function as adding control information and implementing error checking mechanisms.