Which statement describes a characteristic of the frame header fields of the data link layer?
a) They all include the flow control and logical connection fields.
b) Ethernet frame header fields contain Layer 3 source and destination addresses.
c) They vary depending on protocols.
d) They include information on user applications.
Correct Answer: c
The frame header fields of the data link layer play a crucial role in the transmission of data over a network. These fields provide essential information for the proper delivery of data frames from the source to the destination.
Let’s examine each statement and its correctness in detail.
a) “They all include the flow control and logical connection fields.”
This statement is not correct. The frame header fields of the data link layer do not necessarily include flow control and logical connection fields. The data link layer primarily deals with the physical addressing and error detection aspects of data transmission.
Flow control and logical connection fields are typically associated with higher layers of the OSI model, such as the transport layer (Layer 4) and the session layer (Layer 5).
The data link layer focuses on tasks like framing, addressing, and error checking to ensure reliable transmission of data frames over the physical medium.
b) “Ethernet frame header fields contain Layer 3 source and destination addresses.”
This statement is not entirely correct either. Ethernet frame headers include Layer 2 addresses, specifically the source and destination MAC (Media Access Control) addresses. These MAC addresses are used for local network communication within the same Ethernet network segment.
Layer 3 addresses, on the other hand, are associated with the network layer (e.g., IP addresses in the case of IPv4 or IPv6). The mapping between Layer 2 (MAC) addresses and Layer 3 (IP) addresses is typically done at the network layer (Layer 3) through protocols like ARP (Address Resolution Protocol).
So, while Ethernet frames do play a role in transporting IP packets, they do not directly contain Layer 3 source and destination addresses in their frame headers.
c) “They vary depending on protocols.”
This statement is correct. The frame header fields of the data link layer can vary significantly depending on the specific network protocol being used. Different data link layer protocols have their own header formats and fields designed to suit their particular requirements.
For example, Ethernet, Wi-Fi, and PPP (Point-to-Point Protocol) are all data link layer protocols with distinct frame header formats.
These formats define how data is framed, addressed, and checked for errors within the scope of that specific protocol. Therefore, the structure and content of frame header fields are protocol-dependent.
d) “They include information on user applications.”
This statement is not correct. The frame header fields of the data link layer are primarily concerned with the lower-level aspects of data transmission, such as addressing, error detection, and frame delineation. They do not contain information related to user applications.
Information about user applications, data content, and higher-layer protocols (e.g., HTTP, FTP, or DNS) is typically encapsulated within the data payload of the frame, which is carried in the higher layers of the OSI model, such as the transport layer (Layer 4) and above.
In summary, the correct characteristic of frame header fields in the data link layer is that they vary depending on protocols. These fields are protocol-specific and define how data frames are structured, addressed, and checked for errors within the scope of a particular data link layer protocol.
They do not include flow control and logical connection fields, do not contain Layer 3 source and destination addresses (but rather Layer 2 addresses), and do not carry information related to user applications.
Understanding these distinctions is essential for designing and troubleshooting network communication at the data link layer.
MBA,BBA.
I am Smirti Bam, an enthusiastic edu blogger with a passion for sharing insights into the dynamic world of business and management through this website.
I hold a MBA degree from Presidential Business School, Kathmandu, and a BBA degree with a specialization in Finance from Apex College,