In data communication at the data link layer, a single logically grouped packet or unit of data transmitted on a link is known as what?

Introduction / Context:
This question is from the area of computer networks, specifically the data link layer in the OSI model. Network protocols break user data into smaller units for transmission over physical media. Each layer of the communication model has a standard name for its data units. Recognising these names is essential for understanding how data moves across networks and is frequently tested in networking sections of exams.

Given Data / Assumptions:

• The focus is on a single packet on a data link.
• We are working at the data link layer of the OSI model.
• Options include frame, group, block, path and route unit.
• The question asks for the standard technical term for that single packet at this layer.

Concept / Approach:
In the OSI model, different layers have different names for the unit of data they handle. At the physical layer, bits are transmitted. At the data link layer, the unit is called a frame. At the network layer, it is usually called a packet. At the transport layer, it may be called a segment or datagram depending on the protocol. Therefore, when a question specifically mentions a single packet on a data link, it is pointing to the term frame. Other terms like group or block are more generic and are not the standard OSI terminology.

Step-by-Step Solution:
Step 1: Recall the OSI layer model and the corresponding data units: bits, frames, packets, segments and so on. Step 2: Identify that the phrase on a data link indicates the data link layer, which is responsible for node to node delivery and framing. Step 3: At the data link layer, protocol specifications such as Ethernet define a frame structure that includes headers, payload data and trailer fields such as checksums. Step 4: Therefore, the correct term for a single unit at this layer is frame. Step 5: The word group is a general English term and does not appear as a standard data unit name in OSI terminology. Step 6: Block can refer to blocks of data in storage or some protocols, but the canonical OSI term for a data link unit is frame. Step 7: Path and route unit refer more to network layer concepts and routing, not to the data link layer transmission unit. Step 8: Thus, frame is the correct answer.

Verification / Alternative check:
Networking textbooks and certification guides typically list a table that maps OSI layers to their data units. For the data link layer, they all use the term frame. Examples include Ethernet frames, HDLC frames and PPP frames. These frames encapsulate network layer packets and add addressing and error detection information. This consistent terminology confirms that the correct name for a single packet on a data link is frame.

Why Other Options Are Wrong:
Group and block are vague and are not used as specific OSI layer unit names in basic networking theory. Path refers to the route that data takes through a network, a concept of the network layer rather than the data link layer. Route unit is not a recognised term in standard literature. None of these accurately describe the data link layer unit in the OSI reference model.

Common Pitfalls:
Students sometimes confuse frames and packets, thinking they are exactly the same. While both are units of data, the word packet is usually reserved for the network layer, and frame is associated with the data link layer. Remembering the order bits, frames, packets, segments can help to correctly map each term to the appropriate OSI layer and avoid misinterpretation in exam questions.

Final Answer:
A single packet of data on a data link at the data link layer is known as a frame.