SAS Link Layer vs Transport Layer: Frame Encapsulation
Short answer
B The statement is false: the SAS transport layer, not the link layer, encapsulates transmitted commands, status, and data into SAS frames and decomposes them.
Question
Key Takeaways
It tests SAS protocol layering and traps candidates who associate "frames" exclusively with the link layer.
This H13-611 question tests the boundary between the SAS link layer and transport layer. The statement is false because command, status, and data encapsulation into SAS frames belongs to the transport layer.
Common mistake: The plausible wrong answer is A (True), because the link layer does handle frame transmission and primitives; however, it does not define command/status/data encapsulation into frames — that is the transport layer's role.
Expert Analysis
Why A is the seductive choice Option A sounds right because the word "link" naturally suggests frames. In many protocol stacks, the link layer is where frames are built, transmitted, and checked, so a candidate may read "SAS frames" and stop there. The statement also mixes a genuine link-layer concern — moving frames across a SAS connection — with a much more specific function: deciding how commands, status, and data are encapsulated into those frames and later decomposed.
Where the statement breaks SAS is layered. The phy layer covers the electrical interface, clocking, and encoding; the link layer handles primitives, frame transmission, flow control, and link-level error handling; the transport layer defines how upper-layer information — SCSI commands, data, and status — is carried in SAS frames. The application layer is where the SCSI command set sits. The question's wording describes transport-layer encapsulation/decomposition, not link-layer framing mechanics. Therefore the assertion that the link layer of SAS defines how commands, status, and data are encapsulated into SAS frames is false. The correct answer is B (False).
Exam takeaway Do not choose A just because frames appear in both layers. Ask what is being encapsulated. Raw frame transfer and primitives belong to the link layer; command/data/status mapping into a frame belongs to the transport layer. This is the exact distinction H13-611-style protocol questions use to separate memorizers from candidates who understand the SAS layer model.
Official Reference
This link opens the official vendor documentation in a new tab.
Exam Strategy
When a protocol-layer question uses verbs like encapsulate, segment, or decompose, map the verb to the layer that owns payload formatting, not the layer that merely moves bits or frames. For SAS, remember phy = electrical/encoding, link = primitives and frame transfer, transport = command/data/status mapping into frames, and application = SCSI/ATA command sets. If an option credits the link layer with command encapsulation, flag it as the likely distractor and choose the transport-layer description.
Frequently Asked Questions
Does the SAS link layer handle frames at all?
Which SAS layer understands SCSI commands?
Why is True tempting on SAS frame questions?
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 1 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 1
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10c5cfe 👍 1 Answered Bit should be transport layer
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